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armchair epidemiology, which Slate described as “convincing but flawed epidemiological analyses.”

The prime example is a Medium blog post titled “Covid-19 — Evidence Over Hysteria” by Aaron Ginn, a Silicon Valley product manager and “growth hacker” who argued against the severity of the virus and condemned the mainstream media for hyping it.

Conservative pundits, who’d spent weeks downplaying the seriousness of the virus, were drawn to Mr. Ginn’s conclusion that “shuttering the local economy is a distraction and arbitrary with limited accretive gain outside of greatly annoying millions and bankrupting hundreds of businesses.”

The Fox News political analyst Brit Hume tweeted the post, and then so did the anchors Bret Baier and Laura Ingraham. Within hours, the blog post was amplified across conservative media.

“I am seeing this playbook more and more,” Dr. Bergstrom said. “Secondhand data showing a crisis narrative that feels just a bit too well crafted. Mixing the truth with the plausible and the plausible with that which seems plausibly true in a week.”

Epidemiologists disagreed, pointing to some of Mr. Ginn’s assumptions as “unsubstantiated” and ignorant of “first-chapter-of-the-epidemiology-textbook stuff.”

After a 31-tweet thread from the infectious-disease expert Carl Bergstrom debunking Mr. Ginn’s data as cherry-picked, Medium took the post down, prompting a backlash in conservative spheres. More than two million people had already viewed it.

Mr. Ginn’s post, which seems informed by his reflexive skepticism of the mainstream media, filled two needs for readers: It offered a scientific-seeming explanation that real scientists would not provide. And it provided a political foil, the media.

This, according to Dr. Bergstrom, is what makes armchair epidemiology so harmful. Posts like Mr. Ginn’s “deplete the critical resource you need to manage the pandemic, which is trust,

“When people are getting conflicting messages, it makes it very hard for state and local authorities to generate the political will to take strong actions downstream.”

At first glance, the piece looked quite convincing. Mr. Ginn drew heavily from charts from the C.D.C., Johns Hopkins and the Financial Times. “You don’t need a special degree to understand what the data says and doesn’t say,” he claimed.

Dr. Bergstrom argues that the advances in available data make it easier than ever for junk-science peddlers to appear legitimate.

“Statistical analysis is a black box to most of us,” Dr. Bergstrom said. “And it’s like, ‘I can’t challenge a multilinear statistical regression because I don’t know what that is,’

“And so a form of authority gets imposed on a reader and we tend not to challenge data the way we’ve learned to challenge words.”

Mr. Evans is concerned that ultimately important nuance will be lost and pro-Trump pundits will use the news to exclusively scapegoat China and divert blame away from domestic failings. “What’s scary is how smart the false stuff is,” he said.

Covid-19 and the immediate threat to public health means that networks like Facebook, Twitter and YouTube have been unusually decisive about taking down misinformation. “In a case of a pandemic like this, when we are seeing posts that are urging people not to get treatment,” Facebook’s chief executive, Mark Zuckerberg, said recently, “that’s a completely different class of content versus the back-and-forth of what candidates may say about each other.”

The Trump administration and right-wing media watchdogs will weaponize changing facts about the virus, pointing to them as proof of a deep state bent on damaging the president or a media apparatus trying to swing an election

Others will try to pin the blame for the pandemic solely on the Trump administration

What we don’t know about Covid-19 will degenerate into ever more intricate conspiracies — some almost believable, some outrageous but all dangerous.

“We’re in a stream of ever-evolving data, and it’s being shaped around cognitive biases, partisanship and preferences embedded in our cultural identities,”

I called Mr. Pomerantsev because the information vacuum around the virus made me think of the title of his earlier book on Russia — “Nothing Is True and Everything Is Possible.

In the absence of new, vetted information, reckless speculation takes its place, muddling our conception of the truth.

in crisis situations — especially early on — our desire for information exceeds our ability to accurately deliver it. Add to this the complexities of epidemiology: exponential growth; statistical modeling; and the slow, methodical nature of responsible science.

Together, they create the ideal conditions for distrust, bad-faith interpretations and political manipulation, the contours of which we’re only beginning to see.

“The really big question that haunts me is, ‘When do we return to reality?’” Mr. Pomerantsev mused over the phone from his own quarantine. “Or is it that in this partisan age absolutely everything is chopped, cut and edited to fit a different view? I’m waiting for society to finally hit up against a shared reality, like diving into the bottom of swimming pool. Instead we just go deeper.”

Kuh and others emphasize that fates are not fixed by early life. "I don't ever want the findings to be interpreted as purely deterministic," says Kuh; she prefers the more optimistic idea that disease risks result from an accumulation of experiences throughout life, and that education, diet or other factors can shift poor trajectories to better ones.

They worried that a vaccine would initially elude scientists, that weary citizens would abandon restrictions despite the risks, that the virus would be with us from now on.

Most experts believed that once the crisis was over, the nation and its economy would revive quickly. But there would be no escaping a period of intense pain.

Exactly how the pandemic will end depends in part on medical advances still to come. It will also depend on how individual Americans behave in the interim. If we scrupulously protect ourselves and our loved ones, more of us will live. If we underestimate the virus, it will find us.

More Americans may die than the White House admits.

The epidemiological model often cited by the White House, which was produced by the University of Washington’s Institute for Health Metrics and Evaluation, originally predicted 100,000 to 240,000 deaths by midsummer. Now that figure is 60,000.

The institute’s projection runs through Aug. 4, describing only the first wave of this epidemic. Without a vaccine, the virus is expected to circulate for years, and the death tally will rise over time.

Fatality rates depend heavily on how overwhelmed hospitals get and what percentage of cases are tested. China’s estimated death rate was 17 percent in the first week of January, when Wuhan was in chaos, according to a Center for Evidence-Based Medicine report, but only 0.7 percent by late February.

Various experts consulted by the Centers for Disease Control and Prevention in March predicted that the virus eventually could reach 48 percent to 65 percent of all Americans, with a fatality rate just under 1 percent, and would kill up to 1.7 million of them if nothing were done to stop the spread.

A model by researchers at Imperial College London cited by the president on March 30 predicted 2.2 million deaths in the United States by September under the same circumstances.

China has officially reported about 83,000 cases and 4,632 deaths, which is a fatality rate of over 5 percent. The Trump administration has questioned the figures but has not produced more accurate ones.

The tighter the restrictions, experts say, the fewer the deaths and the longer the periods between lockdowns. Most models assume states will eventually do widespread temperature checks, rapid testing and contact tracing, as is routine in Asia.

In this country, hospitals in several cities, including New York, came to the brink of chaos.

Only when tens of thousands of antibody tests are done will we know how many silent carriers there may be in the United States. The C.D.C. has suggested it might be 25 percent of those who test positive. Researchers in Iceland said it might be double that.

China is also revising its own estimates. In February, a major study concluded that only 1 percent of cases in Wuhan were asymptomatic. New research says perhaps 60 percent were.

The virus may also be mutating to cause fewer symptoms. In the movies, viruses become more deadly. In reality, they usually become less so, because asymptomatic strains reach more hosts. Even the 1918 Spanish flu virus eventually faded into the seasonal H1N1 flu.

The lockdowns will end, but haltingly.

it is likely a safe bet that at least 300 million of us are still vulnerable.

Until a vaccine or another protective measure emerges, there is no scenario, epidemiologists agreed, in which it is safe for that many people to suddenly come out of hiding. If Americans pour back out in force, all will appear quiet for perhaps three weeks.

The gains to date were achieved only by shutting down the country, a situation that cannot continue indefinitely. The White House’s “phased” plan for reopening will surely raise the death toll no matter how carefully it is executed.

Every epidemiological model envisions something like the dance

On the models, the curves of rising and falling deaths resemble a row of shark teeth.

Surges are inevitable, the models predict, even when stadiums, churches, theaters, bars and restaurants remain closed, all travelers from abroad are quarantined for 14 days, and domestic travel is tightly restricted to prevent high-intensity areas from reinfecting low-intensity ones.

In his wildly popular March 19 article in Medium, “Coronavirus: The Hammer and the Dance,” Tomas Pueyo correctly predicted the national lockdown, which he called the hammer, and said it would lead to a new phase, which he called the dance, in which essential parts of the economy could reopen, including some schools and some factories with skeleton crews.

Even the “Opening Up America Again” guidelines Mr. Trump issued on Thursday have three levels of social distancing, and recommend that vulnerable Americans stay hidden. The plan endorses testing, isolation and contact tracing — but does not specify how these measures will be paid for, or how long it will take to put them in place.

On Friday, none of that stopped the president from contradicting his own message by sending out tweets encouraging protesters in Michigan, Minnesota and Virginia to fight their states’ shutdowns.

China did not allow Wuhan, Nanjing or other cities to reopen until intensive surveillance found zero new cases for 14 straight days, the virus’s incubation period.

Compared with China or Italy, the United States is still a playground.Americans can take domestic flights, drive where they want, and roam streets and parks. Despite restrictions, everyone seems to know someone discreetly arranging play dates for children, holding backyard barbecues or meeting people on dating apps.

Even with rigorous measures, Asian countries have had trouble keeping the virus under control

But if too many people get infected at once, new lockdowns will become inevitable. To avoid that, widespread testing will be imperative.

Reopening requires declining cases for 14 days, the tracing of 90 percent of contacts, an end to health care worker infections, recuperation places for mild cases and many other hard-to-reach goals.

Immunity will become a societal advantage.

Imagine an America divided into two classes: those who have recovered from infection with the coronavirus and presumably have some immunity to it; and those who are still vulnerable.

“It will be a frightening schism,” Dr. David Nabarro, a World Health Organization special envoy on Covid-19, predicted. “Those with antibodies will be able to travel and work, and the rest will be discriminated against.”

Soon the government will have to invent a way to certify who is truly immune. A test for IgG antibodies, which are produced once immunity is established, would make sense

Dr. Fauci has said the White House was discussing certificates like those proposed in Germany. China uses cellphone QR codes linked to the owner’s personal details so others cannot borrow them.

As Americans stuck in lockdown see their immune neighbors resuming their lives and perhaps even taking the jobs they lost, it is not hard to imagine the enormous temptation to join them through self-infection

My daughter, who is a Harvard economist, keeps telling me her age group needs to have Covid-19 parties to develop immunity and keep the economy going,”

It would be a gamble for American youth, too. The obese and immunocompromised are clearly at risk, but even slim, healthy young Americans have died of Covid-19.

The virus can be kept in check, but only with expanded resources.

Resolve to Save Lives, a public health advocacy group run by Dr. Thomas R. Frieden, the former director of the C.D.C., has published detailed and strict criteria for when the economy can reopen and when it must be closed.

once a national baseline of hundreds of thousands of daily tests is established across the nation, any viral spread can be spotted when the percentage of positive results rises.

To keep the virus in check, several experts insisted, the country also must start isolating all the ill — including mild cases.

“If I was forced to select only one intervention, it would be the rapid isolation of all cases,”

In China, anyone testing positive, no matter how mild their symptoms, was required to immediately enter an infirmary-style hospital — often set up in a gymnasium or community center outfitted with oxygen tanks and CT scanners.

There, they recuperated under the eyes of nurses. That reduced the risk to families, and being with other victims relieved some patients’ fears.

Still, experts were divided on the idea of such wards

Ultimately, suppressing a virus requires testing all the contacts of every known case. But the United States is far short of that goal.

In China’s Sichuan Province, for example, each known case had an average of 45 contacts.

The C.D.C. has about 600 contact tracers and, until recently, state and local health departments employed about 1,600, mostly for tracing syphilis and tuberculosis cases.

China hired and trained 9,000 in Wuhan alone. Dr. Frieden recently estimated that the United States will need at least 300,000.

There will not be a vaccine soon.

any effort to make a vaccine will take at least a year to 18 months.

the record is four years, for the mumps vaccine.

for unclear reasons, some previous vaccine candidates against coronaviruses like SARS have triggered “antibody-dependent enhancement,” which makes recipients more susceptible to infection, rather than less. In the past, vaccines against H.I.V. and dengue have unexpectedly done the same.

A new vaccine is usually first tested in fewer than 100 young, healthy volunteers. If it appears safe and produces antibodies, thousands more volunteers — in this case, probably front-line workers at the highest risk — will get either it or a placebo in what is called a Phase 3 trial.

It is possible to speed up that process with “challenge trials.” Scientists vaccinate small numbers of volunteers, wait until they develop antibodies, and then “challenge” them with a deliberate infection to see if the vaccine protects them.

Normally, it is ethically unthinkable to challenge subjects with a disease with no cure, such as Covid-19.

“Fewer get harmed if you do a challenge trial in a few people than if you do a Phase 3 trial in thousands,” said Dr. Lipsitch, who recently published a paper advocating challenge trials in the Journal of Infectious Diseases. Almost immediately, he said, he heard from volunteers.

The hidden danger of challenge trials, vaccinologists explained, is that they recruit too few volunteers to show whether a vaccine creates enhancement, since it may be a rare but dangerous problem.

if a vaccine is invented, the United States could need 300 million doses — or 600 million if two shots are required. And just as many syringes.

“People have to start thinking big,” Dr. Douglas said. “With that volume, you’ve got to start cranking it out pretty soon.”

Treatments are likely to arrive first.

The modern alternative is monoclonal antibodies. These treatment regimens, which recently came very close to conquering the Ebola epidemic in eastern Congo, are the most likely short-term game changer, experts said.

as with vaccines, growing and purifying monoclonal antibodies takes time. In theory, with enough production, they could be used not just to save lives but to protect front-line workers.

Having a daily preventive pill would be an even better solution, because pills can be synthesized in factories far faster than vaccines or antibodies can be grown and purified.

Goodbye, ‘America First.’

A public health crisis of this magnitude requires international cooperation on a scale not seen in decades. Yet Mr. Trump is moving to defund the W.H.O., the only organization capable of coordinating such a response.

And he spent most of this year antagonizing China, which now has the world’s most powerful functioning economy and may become the dominant supplier of drugs and vaccines. China has used the pandemic to extend its global influence, and says it has sent medical gear and equipment to nearly 120 countries.

This is not a world in which “America First” is a viable strategy, several experts noted.

“If President Trump cares about stepping up the public health efforts here, he should look for avenues to collaborate with China and stop the insults,”

If we alienate the Chinese with our rhetoric, I think it will come back to bite us,” he said.“What if they come up with the first vaccine? They have a choice about who they sell it to. Are we top of the list? Why would we be?”

Once the pandemic has passed, the national recovery may be swift. The economy rebounded after both world wars, Dr. Mulder noted.

In one of the most provocative analyses in his follow-up article, “Coronavirus: Out of Many, One,” Mr. Pueyo analyzed Medicare and census data on age and obesity in states that recently resisted shutdowns and counties that voted Republican in 2016.

He calculated that those voters could be 30 percent more likely to die of the virus.

In the periods after both wars, Dr. Mulder noted, society and incomes became more equal. Funds created for veterans’ and widows’ pensions led to social safety nets, measures like the G.I. Bill and V.A. home loans were adopted, unions grew stronger, and tax benefits for the wealthy withered.

If a vaccine saves lives, many Americans may become less suspicious of conventional medicine and more accepting of science in general — including climate change

it would probably be many years until it was safe enough to “return to approximately the lifestyle we had.” She said, “We have to settle to live with the virus.”

Epidemiologists are worried about many unknowns, including how long immunity lasts; how the virus may mutate; the challenges of vaccine distribution; and the possible reluctance to accept the vaccine among some groups.

the epidemiologists are living with stringent precautions and new workarounds in place, far stricter than those of many ordinary Americans

Most scientists say around 70 percent of the population will need to be immune for the United States to reach herd immunity, when the virus slows down significantly or stops

Three-quarters of respondents said they planned to spend Christmas, Hanukkah or other winter holidays only with members of their household, or not celebrate at all, similar to how they spent Thanksgiving.

most epidemiologists agreed on these general principles: They are less worried about outdoor activities and about touching surfaces, and more worried about indoor activities and those with large groups.

“Indoor venues with lots of people is the riskiest situation,” said Leland Ackerson of the University of Massachusetts. “Outdoors with few people, social distancing and precautions is the least risky.” He said that during the last month, he had hiked with friends, opened mail without precautions and run errands.

“It’s funny: When you asked this before, I was so optimistic about the U.S. being able to lead and address this in a timely fashion,” said Rachel Widome, associate professor at the University of Minnesota. “I told you I thought things would be better by now. I was very wrong. They are dramatically worse.”

Of 23 activities of daily life that the survey asked about, there were only three that the majority of respondents had done in the last month: gathering outdoors with friends; bringing in mail without precautions; and running errands, like going to the grocery store or pharmacy.

Nearly a third of respondents said they would be comfortable returning to more activities of daily life once they were vaccinated. Some said they would feel comfortable doing only certain things, like socializing with people who had also been vaccinated

A few said they would wait until the country had reached the herd immunity threshold and they had received a vaccine themselves.

“I would do some minimal travel, small indoor gatherings with other close relatives when I am vaccinated, but maintain safety precautions such as wearing a mask and social distance.”

Some said they were less worried than last spring about socializing outdoors, touching surfaces or sending young children to school. They were more worried about indoor air transmission and the dangers of not wearing masks.

“It entirely depends upon what we do as a nation to address the pandemic,” said Emeli Anderson, a doctoral student of epidemiology at Emory. “Right now, we are not nearly doing enough.”

Many epidemiologists expressed disappointment and frustration that public health messaging had not been more effective, and that a growing share of Americans seemed to distrust science. They feared that the politicization of measures like wearing masks and staying home would have long-term consequences.

“This virus has humbled me as a professional and a person,” said Michelle Odden, associate professor of epidemiology at Stanford. “I did not think this level of failure in a federal response was possible in the United States. We have a lot of work to do.”

assuming a highly effective therapeutic drug isn’t developed, a significant number said it would be at least a year before they felt it would be safe to do many of the things they used to.

“I expect that wearing a mask will become part of my daily life, moving forward, even after a vaccine is deployed,”

Many said they planned to keep working from home at least part of the time. Some said they would always be more hesitant about greeting people with a handshake or a hug, being in crowded places or traveling internationally.

“I think it will be a few years before gathering with large groups of people in crowded public places and being on airplanes and other public transportation will feel safe to me,”

Others cautioned that even when the physical dangers of the pandemic recede, other consequences are likely to be long-lasting. They mentioned the effects of isolation on children’s developing brains; the exposure of deep inequities in health care and in safety nets; and the fear and sadness of so much illness and death.

t the beginning of this century, journalism was in extremis. Recessions, coupled with readers’ changing habits, prodded media companies to gamble on a digital future unencumbered by the clunky apparatus of publishing on paper. Over a decade, the number of newspaper employees dropped by 38 percent. As journalism shriveled, its prestige plummeted. One report ranked newspaper reporter as the worst job in America. The profession found itself forced to reconsider its very reasons for existing. All the old nostrums about independence suddenly seemed like unaffordable luxuries.

My master was Chartbeat, a site that provides writers, editors, and their bosses with a real-time accounting of web traffic, showing the flickering readership of each and every article. Chartbeat and its competitors have taken hold at virtually every magazine, newspaper, and blog. With these meters, no piece has sufficient traffic—it can always be improved with a better headline, a better approach to social media, a better subject, a better argument

Upworthy would write 25 different headlines, test all of them, and determine the most clickable of the bunch. Based on these results, it uncovered syntactical patterns that almost ensured hits. Classic examples: “9 out of 10 Americans Are Completely Wrong About This Mind-Blowing Fact” and “You Won’t Believe What Happened Next.” These formulas became commonplace on the web, until readers grew wise to them.

The core insight of Upworthy, BuzzFeed, Vox Media, and other emerging internet behemoths was that editorial success could be engineered, if you listened to the data. This insight was embraced across the industry and wormed its way into the New Republic.

Jonah Peretti, the founder of BuzzFeed, had put this way: R = ßz. (In epidemiology, ß represents the probability of transmission; z is the number of people exposed to a contagious individual.) The equation supposedly illustrates how a piece of content could go viral. But although Peretti got the idea for his formula from epidemiology, the emerging science of traffic was really a branch of behavioral science: People clicked so quickly, they didn’t always fully understand why. These decisions were made in a semiconscious state, influenced by cognitive biases. Enticing a reader entailed a little manipulation, a little hidden persuasion.

The new generation of media giants has no patience for the old ethos of detachment. It’s not that these companies don’t have aspirations toward journalistic greatness. BuzzFeed, Vice, and the Huffington Post invest in excellent reporting and employ first-rate journalists—and they have produced some of the most memorable pieces of investigative journalism in this century. But the pursuit of audience is their central mission. They have allowed the endless feedback loop of the web to shape their editorial sensibility, to determine their editorial investments

this is just a digitally enhanced version of an old-fashioned media pile-on. But social media amplify the financial incentive to join the herd. The results are highly derivative. Joshua Topolsky, a founder of The Verge, has bemoaned this creeping homogenization: “Everything looks the same, reads the same, and seems to be competing for the same eyeballs.”

Donald Trump is the culmination of the era. He understood how, more than at any other moment in recent history, the media need to give the public the circus that it desires. Even if the media disdained Trump’s outrages, they built him up as a plausible candidate, at which point they had no choice but to cover him. Stories about Trump yielded the sort of traffic that pleased the data gods and benefited the bottom line.

We were idealistic about our shared idealism. But my vision of the world was moralistic and romantic; his was essentially technocratic. He had faith in systems—rules, efficiencies, organizational charts, productivity tools

Makers of magazines and newspapers used to think of their product as a coherent package—an issue, an edition, an institution. They did not see themselves as the publishers of dozens of discrete pieces to be trafficked each day on Facebook, Twitter, and Google.

Thinking about bundling articles into something larger was intellectually liberating. Editors justified high-minded and quixotic articles as essential for “the mix.

Journalism has performed so admirably in the aftermath of Trump’s victory that it has grown harder to see the profession’s underlying rot. Now each assignment is subjected to a cost-benefit analysis—will the article earn enough traffic to justify the investment? Sometimes the analysis is explicit and conscious, though in most cases it’s subconscious and embedded in euphemism. Either way, it’s this train of thought that leads editors to declare an idea “not worth the effort” or to worry about whether an article will “sink.”

CNN chief medical correspondent Dr. Sanjay Gupta said that the coronavirus could spread at protests depending on factors like mask-wearing, how closely people gathered, and how long people stayed in close contact.

"It is a contagious virus. People being outside, people wearing masks, people moving by each other more quickly may reduce the likelihood of significant exponential growth. But that's still the concern."

The virus has particularly impacted African-Americans, who make up a disproportionate percentage of Covid-19 cases and deaths.

For one, the textbook combination of identification, isolation and quarantine for contacts helped stop the potential spread of coronavirus an Air Force basic training camp. Military doctors said their approach kept the case count to just five among 10,000 recruits at Joint Base San Antonio-Lackland in Texas in March and April.

The base used techniques including quarantine, social distancing, early trainee screening, rapid isolation and monitored re-entry to slow the transmission, the researchers said in a report published by the US Centers for Disease Control and Prevention Tuesday.

"Climate only would become an important seasonal factor in controlling COVID-19 once a large proportion of people within a given community are immune or resistant to infection," Collins wrote, citing experts in infectious disease transmission and climate modeling.

The US should have 100 million doses of one candidate Covid-19 vaccine by the end of the year, Dr. Anthony Fauci, the director of the National Institute of Allergy and Infectious Diseases (NIAID) and a member of the White House coronavirus task force, said Tuesday.

Being in close proximity to people I don’t know will always feel less safe than it used to,” said Ellicott Matthay, a postdoctoral scholar at the University of California, San Francisco.

Three-quarters of respondents said they planned to spend Christmas, Hanukkah or other winter holidays only with members of their household, or not celebrate at all, similar to how they spent Thanksgiving.

Most scientists say around 70 percent of the population will need to be immune for the United States to reach herd immunity, when the virus slows down significantly or stops.

Nearly a third of respondents said they would be comfortable returning to more activities of daily life once they were vaccinated.

Since the spring, 79 percent of the epidemiologists said their assessment of various risks had changed, and that they had adjusted their behaviors accordingly. Science is a process, they said, and the virus is new, so even those studying it most closely have learned things along the way.

“It entirely depends upon what we do as a nation to address the pandemic,” said Emeli Anderson, a doctoral student of epidemiology at Emory. “Right now, we are not nearly doing enough.”

Many epidemiologists expressed disappointment and frustration that public health messaging had not been more effective, and that a growing share of Americans seemed to distrust science.

“This virus has humbled me as a professional and a person,” said Michelle Odden, associate professor of epidemiology at Stanford. “I did not think this level of failure in a federal response was possible in the United States. We have a lot of work to do.”

As for the future, some said that parts of life could begin to return to normal sometime in the summer, thanks to vaccines. B

ut assuming a highly effective therapeutic drug isn’t developed, a significant number said it would be at least a year before they felt it would be safe to do many of the things they used to.

Many said they planned to keep working from home at least part of the time. Some said they would always be more hesitant about greeting people with a handshake or a hug, being in crowded places or traveling internationally.

more significant, we are not very good at predicting who is likely to be dangerous in the future.

“Most of these killers are young men who are not floridly psychotic. They tend to be paranoid loners who hold a grudge and are full of rage.”

Even though we know from large-scale epidemiologic studies like the E.C.A. study that a young psychotic male who is intoxicated with alcohol and has a history of involuntary commitment is at a high risk of violence, most individuals who fit this profile are harmless.

“Can we reliably predict violence?  ‘No’ is the short answer. Psychiatrists, using clinical judgment, are not much better than chance at predicting which individual patients will do something violent and which will not.”

Even if clinicians could predict violence perfectly, keeping guns from people with mental illness is easier said than done. Nearly five years after Congress enacted the National Instant Criminal Background Check System, only about half of the s

All the focus on the small number of people with mental illness who are violent serves to make us feel safer by displacing and limiting the threat of violence to a small, well-defined group

But the sad and frightening truth is that the vast majority of homicides are carried out by outwardly normal people in the grip of all too ordinary human aggression to whom we provide nearly unfettered access to deadly force.

the mouth feel of soda and many other food items, especially those high in fat, is second only to the bliss point in its ability to predict how much craving a product will induce.

He organized focus-group sessions with the people most responsible for buying bologna — mothers — and as they talked, he realized the most pressing issue for them was time. Working moms strove to provide healthful food, of course, but they spoke with real passion and at length about the morning crush, that nightmarish dash to get breakfast on the table and lunch packed and kids out the door.

as the focus swung toward kids, Saturday-morning cartoons started carrying an ad that offered a different message: “All day, you gotta do what they say,” the ads said. “But lunchtime is all yours.”

When it came to Lunchables, they did try to add more healthful ingredients. Back at the start, Drane experimented with fresh carrots but quickly gave up on that, since fresh components didn’t work within the constraints of the processed-food system, which typically required weeks or months of transport and storage before the food arrived at the grocery store. Later, a low-fat version of the trays was developed, using meats and cheese and crackers that were formulated with less fat, but it tasted inferior, sold poorly and was quickly scrapped.

One of the company’s responses to criticism is that kids don’t eat the Lunchables every day — on top of which, when it came to trying to feed them more healthful foods, kids themselves were unreliable. When their parents packed fresh carrots, apples and water, they couldn’t be trusted to eat them. Once in school, they often trashed the healthful stuff in their brown bags to get right to the sweets.

This idea — that kids are in control — would become a key concept in the evolving marketing campaigns for the trays. In what would prove to be their greatest achievement of all, the Lunchables team would delve into adolescent psychology to discover that it wasn’t the food in the trays that excited the kids; it was the feeling of power it brought to their lives.

The prevailing attitude among the company’s food managers — through the 1990s, at least, before obesity became a more pressing concern — was one of supply and demand. “People could point to these things and say, ‘They’ve got too much sugar, they’ve got too much salt,’ ” Bible said. “Well, that’s what the consumer wants, and we’re not putting a gun to their head to eat it. That’s what they want. If we give them less, they’ll buy less, and the competitor will get our market. So you’re sort of trapped.”

at last count, including sales in Britain, they were approaching the $1 billion mark. Lunchables was more than a hit; it was now its own category

he holds the entire industry accountable. “What do University of Wisconsin M.B.A.’s learn about how to succeed in marketing?” his presentation to the med students asks. “Discover what consumers want to buy and give it to them with both barrels. Sell more, keep your job! How do marketers often translate these ‘rules’ into action on food? Our limbic brains love sugar, fat, salt. . . . So formulate products to deliver these. Perhaps add low-cost ingredients to boost profit margins. Then ‘supersize’ to sell more. . . . And advertise/promote to lock in ‘heavy users.’ Plenty of guilt to go around here!”

men in the eastern part of Finland had the highest rate of fatal cardiovascular disease in the world. Research showed that this plague was not just a quirk of genetics or a result of a sedentary lifestyle — it was also owing to processed foods. So when Finnish authorities moved to address the problem, they went right after the manufacturers. (The Finnish response worked. Every grocery item that was heavy in salt would come to be marked prominently with the warning “High Salt Content.” By 2007, Finland’s per capita consumption of salt had dropped by a third, and this shift — along with improved medical care — was accompanied by a 75 percent to 80 percent decline in the number of deaths from strokes and heart disease.)

I tracked Lin down in Irvine, Calif., where we spent several days going through the internal company memos, strategy papers and handwritten notes he had kept. The documents were evidence of the concern that Lin had for consumers and of the company’s intent on using science not to address the health concerns but to thwart them. While at Frito-Lay, Lin and other company scientists spoke openly about the country’s excessive consumption of sodium and the fact that, as Lin said to me on more than one occasion, “people get addicted to salt

the marketing team was joined by Dwight Riskey, an expert on cravings who had been a fellow at the Monell Chemical Senses Center in Philadelphia, where he was part of a team of scientists that found that people could beat their salt habits simply by refraining from salty foods long enough for their taste buds to return to a normal level of sensitivity. He had also done work on the bliss point, showing how a product’s allure is contextual, shaped partly by the other foods a person is eating, and that it changes as people age. This seemed to help explain why Frito-Lay was having so much trouble selling new snacks. The largest single block of customers, the baby boomers, had begun hitting middle age. According to the research, this suggested that their liking for salty snacks — both in the concentration of salt and how much they ate — would be tapering off.

Riskey realized that he and his colleagues had been misreading things all along. They had been measuring the snacking habits of different age groups and were seeing what they expected to see, that older consumers ate less than those in their 20s. But what they weren’t measuring, Riskey realized, is how those snacking habits of the boomers compared to themselves when they were in their 20s. When he called up a new set of sales data and performed what’s called a cohort study, following a single group over time, a far more encouraging picture — for Frito-Lay, anyway — emerged. The baby boomers were not eating fewer salty snacks as they aged. “In fact, as those people aged, their consumption of all those segments — the cookies, the crackers, the candy, the chips — was going up,” Riskey said. “They were not only eating what they ate when they were younger, they were eating more of it.” In fact, everyone in the country, on average, was eating more salty snacks than they used to. The rate of consumption was edging up about one-third of a pound every year, with the average intake of snacks like chips and cheese crackers pushing past 12 pounds a year

Riskey had a theory about what caused this surge: Eating real meals had become a thing of the past.

“We looked at this behavior, and said, ‘Oh, my gosh, people were skipping meals right and left,’ ” Riskey told me. “It was amazing.” This led to the next realization, that baby boomers did not represent “a category that is mature, with no growth. This is a category that has huge growth potential.”

The food technicians stopped worrying about inventing new products and instead embraced the industry’s most reliable method for getting consumers to buy more: the line extension.

He zeroed right in on the Cheetos. “This,” Witherly said, “is one of the most marvelously constructed foods on the planet, in terms of pure pleasure.” He ticked off a dozen attributes of the Cheetos that make the brain say more. But the one he focused on most was the puff’s uncanny ability to melt in the mouth. “It’s called vanishing caloric density,” Witherly said. “If something melts down quickly, your brain thinks that there’s no calories in it . . . you can just keep eating it forever.”

Frito-Lay acquired Stacy’s Pita Chip Company, which was started by a Massachusetts couple who made food-cart sandwiches and started serving pita chips to their customers in the mid-1990s. In Frito-Lay’s hands, the pita chips averaged 270 milligrams of sodium — nearly one-fifth a whole day’s recommended maximum for most American adults — and were a huge hit among boomers.

There’s a paradox at work here. On the one hand, reduction of sodium in snack foods is commendable. On the other, these changes may well result in consumers eating more. “The big thing that will happen here is removing the barriers for boomers and giving them permission to snack,” Carey said. The prospects for lower-salt snacks were so amazing, he added, that the company had set its sights on using the designer salt to conquer the toughest market of all for snacks: schools

The company’s chips, he wrote, were not selling as well as they could for one simple reason: “While people like and enjoy potato chips, they feel guilty about liking them. . . . Unconsciously, people expect to be punished for ‘letting themselves go’ and enjoying them.” Dichter listed seven “fears and resistances” to the chips: “You can’t stop eating them; they’re fattening; they’re not good for you; they’re greasy and messy to eat; they’re too expensive; it’s hard to store the leftovers; and they’re bad for children.” He spent the rest of his memo laying out his prescriptions, which in time would become widely used not just by Frito-Lay but also by the entire industry.

Dichter advised Frito-Lay to move its chips out of the realm of between-meals snacking and turn them into an ever-present item in the American diet. “The increased use of potato chips and other Lay’s products as a part of the regular fare served by restaurants and sandwich bars should be encouraged in a concentrated way,”

the largest weight-inducing food was the potato chip. The coating of salt, the fat content that rewards the brain with instant feelings of pleasure, the sugar that exists not as an additive but in the starch of the potato itself — all of this combines to make it the perfect addictive food. “The starch is readily absorbed,” Eric Rimm, an associate professor of epidemiology and nutrition at the Harvard School of Public Health and one of the study’s authors, told me. “More quickly even than a similar amount of sugar. The starch, in turn, causes the glucose levels in the blood to spike” — which can result in a craving for more.

If Americans snacked only occasionally, and in small amounts, this would not present the enormous problem that it does. But because so much money and effort has been invested over decades in engineering and then relentlessly selling these products, the effects are seemingly impossible to unwind.

Todd Putman, who worked at Coca-Cola from 1997 to 2001, said the goal became much larger than merely beating the rival brands; Coca-Cola strove to outsell every other thing people drank, including milk and water. The marketing division’s efforts boiled down to one question, Putman said: “How can we drive more ounces into more bodies more often?”

“Americans don’t really grasp how pollution impacts their lives,” said Drew Shindell, a professor of Earth science at Duke University and the study’s lead author. “You say, ‘My uncle went to the hospital and died of a heart attack.’ You don’t say the heart attack was caused by air pollution, so we don’t know. It’s still a big killer here. It’s much bigger than from people who die from plane crashes or war or terrorism, but we don’t see the link so clearly

The models calculated about 7 million deaths per year if governments fail to work toward zero emissions by the end of the century, starting today.

they “calculated the human health impacts of pollution exposure under each scenario all over the world — but focusing on results in major cities — using well-established epidemiological models based on decades of public health data on air-pollution related deaths,”

Shindell used an automaker’s problem with faulty ignition switches in 2014 to further illustrate his point. When the switches failed, more than 3 million recalls were involved and auto executives were summoned to Washington to testify before Congress. “But the combined tailpipes of automobiles kill dozens and dozens more people than faulty ignition switches,” the researcher said. “We should be far more worried about pollution than the things we actually worry about.

“There’s got to be a significant amount of progress within the 2020s or it’s too late,” Shindell said. Even for the researchers, it’s a pie-in-the-sky goal, given that South Asian nations such as India, where pollution is among the worst in the world, argue correctly that their per-capita use is small compared with historical use in the Western Hemisphere and that they should be allowed time to develop just as other countries did.

The rules almost certainly mean that the United States is still greatly understating the number of people nationwide who are sick with COVID-19, experts say. There are more than 1,800 discovered coronavirus cases in the United States, but estimates of the outbreak using statistical and genetic models suggest that thousands of people are already sick.

The CDC guidelines—which do not carry legal force—allow for testing a wider array of patients than is currently allowed under many state-level rules. Under guidelines updated earlier this week, the agency noted that “priorities for testing” may include severely ill hospitalized patients with no other diagnosis; symptomatic adults who are older or who have a complicating factor, such as heart disease or a suppressed immune system; and any patient who had close contact with a “suspect or laboratory-confirmed” COVID-19 patient.

But the guidelines may also keep doctors from understanding the “local epidemiology”—that is, the extent of the coronavirus’s spread—in their own region.

Most state guidelines do not apply to tests conducted by private laboratory firms that do routine medical testing, such as Quest Diagnostics and LabCorp. Those firms say they can test 5,000 people a day, combined, but they take three to four days to deliver results, compared with 24 hours for a state public-health or on-site hospital lab test.

we have enough information to know this virus is rapidly transmissible and lethal.

The qualities we most need in a president during this crisis are calmness, wisdom, and reassurance; a command of the facts and the ability to communicate them well; and the capacity to think about the medium and long term while carefully weighing competing options and conflicting needs

We need a leader who can persuade the public to act in ways that are difficult but necessary, who can focus like a laser beam on a problem for a sustained period of time, and who will listen to—and, when necessary, defer to—experts who know far more than he does.

We need a president who can draw the nation together rather than drive it apart, who excels at the intricate work of governing, and who works well with elected officials at every level. We need a chief executive whose judgment is not just sound, but exceptional.

There are some 325 million people in America, and it’s hard to think of more than a handful who are more lacking in these qualities than Donald Trump.

This president does not have the capacity to listen to, synthesize, and internalize information that does not immediately serve his greatest needs: praise, fealty, adoration.

Let’s start with what we know

Someone with Trump’s psychological makeup, when faced with facts and events that are unpleasant, that he perceives as a threat to his self-image and public standing, simply denies them.

After a few days in which he was willing to acknowledge the scope and scale of this crisis—he declared himself a “wartime president”—he has now regressed to type, once again becoming a fountain of misinformation

the coronavirus pandemic may lead to a rapid and even more worrisome psychological and emotional deterioration in the commander in chief.

a former White House adviser who has worked on past pandemics told me, “This fool will bring the death of thousands needlessly. We have mobilized as a country to shut things down for a time, despite the difficulty. We can work our way back to a semblance of normality if we hold out and let the health system make it through the worst of it.” He added, “But now our own president is undoing all that work and preaching recklessness. Rather than lead us in taking on a difficult challenge, he is dragging us toward failure and suffering. Beyond belief.”

The thing to understand about Donald Trump is that putting others before self is not something he can do, even temporarily. His attempts to convey facts that don’t serve his perceived self-interest or to express empathy are forced, scripted, and always short-lived, since such reactions are alien to him.

As one person who consults with the Trump White House on the coronavirus response put it to me, “He has chosen to imagine the worst is behind us when the worst is clearly ahead of us.”

“He finds it intolerable when those things are missing,” a clinical psychologist told me. “Praise, applause, and accolades seem to calm him and boost his confidence. There’s no room for that now, and so he’s growing irritable and needing to create some way to get some positive attention.”

Trump’s success as a politician has been built on his ability to impose his will and narrative on others, to use his experience on a reality-television show and his skill as a con man to shape public impressions in his favor, even—or perhaps, especially—if those impressions are at odds with reality.

Spin and lies about COVID-19, including that it will soon magically disappear, as Trump claimed it would, don’t work. In fact, they have the opposite effect. Misinformation will cause the virus to increase its deadly spread.

So as the crisis deepens—as the body count increases, hospitals are overwhelmed, and the economy contracts, perhaps dramatically—it’s reasonable to assume that the president will reach for the tools he has used throughout his life: duplicity and denial.

What happens if the tricks that have allowed him to walk away from scandal after scandal don’t work quite so well, if the doors of escape are bolted shut, and if it dawns on even some of his supporters—people who will watch family members, friends, and neighbors contract the disease, some number of whom will die—that no matter what Trump says, he can’t alter this epidemiological reality?

As the health-care and economic crises worsen, Trump’s hallmarks will be even more fully on display. The president will create new scapegoats

He will try to create an alternate story to distract people from an inconvenient truth—but in this case, the public is too afraid, the story is too big, and the carnage will be too great to be distracted from it.

America will make it to the other side of this crisis, as it has after every other crisis. But the struggle will be a good deal harder, and the human cost a good deal higher, because we elected as president a man who is so damaged and so broken in so many ways.

Just as a return to even a new normal is unthinkable for the foreseeable future — and well past Easter, Mr. Trump — a complete shutdown and shelter-in-place strategy cannot last for months

A middle-ground approach is the only realistic one — and defining what that looks like means doing our best to keep all such workers safe.

In three to four weeks, there will be a major shortage of chemical reagents for coronavirus testing

When leaders tell the truth about even near-desperate situations, when they lay out a clear and understandable vision, the public might remain frightened, but it will act rationally and actively participate in the preservation of its safety and security.

begin by stating a number of hard truth

The first is that no matter what we do at this stage, numerous hospitals in the United States will be overrun. Many people, including health care workers, will get sick and some will die. And the economy will tank. It’s too late to change any of this now.

It also means leadership. Above all, it means being realistic about what is possible and what is not, and communicating that clearly to the American public.

Much better, instead, to immediately gear up for epidemic intelligence

it simply won’t be available.

The second hard truth is that at this stage, any public health response that counts on widespread testing in the United States is doomed to fail.

illness surveillance, in which epidemiologists survey a sample of doctors’ offices in a given geographic region each day to learn how many patients sought care for illnesses with symptoms of fever, cough and muscle aches.

A third hard truth is that shortages of personal protective equipment — particularly N-95 masks — for health care workers will only get worse in the United States as global need continues to rise precipitously

If you can’t make nearly enough masks to meet the need, then you must conserve the masks you can make. Unfortunately, some hospitals in the United States are not employing science-based methods for conserving these invaluable lifesaving masks.

Making ventilators — machines that breathe for patients who cannot effectively do so on their own — poses an even more formidable challenge

a Medtronic ventilator has about 1,500 parts, supplied by 14 separate countries.

More machines might, at best, be manufactured by the hundreds a month — but not by the thousands, as is needed right now.

a national strategy and leadership are crucial. Otherwise, hospitals, governors and politicians will only vie against one anothe

“Respirators, ventilators, all of the equipment — try getting it yourselves,” Mr. Trump said

This is exactly the wrong message. The White House must take charge, keeping track of national inventory, purchasing the precious resources and distributing them where they are most needed at the moment.

More than anything, what the United States needs right now is for the president to undertake an intellectual Manhattan Project: gather the best minds in public health, medicine, medical ethics, catastrophe preparedness and response; political leadership; and private-sector manufacturing and the pharmaceutical industry.

The effort against Covid-19 will need to be bear fruit within days — and come up with a comprehensive but realistic blueprint for getting America through the next 12 to 18 months, or however long it takes for a vaccine to become widely available or herd immunity to take hold in the population

You can fault George W. Bush in any number of ways, but he did not spend the months before 9/11 repeatedly telling the public that there was absolutely no threat of a terrorist attack on our soil or boasting that he had it all under control, or claiming Osama bin Laden was a liberal hoax to delegitimize his presidency and wreck the economy.

Bret: The inability of so much of the public to remember what Trump was saying just a month ago suggests that, in addition to the coronavirus crisis, we’re also experiencing a national amnesia pandemic.

here’s my fear: the Biden campaign reminds me a bit of John McCain’s 2008 campaign — minus the Sarah Palin part, of course. McCain started off as the presumptive front-runner, then nearly ran out of gas before making a miraculous primary comeback. But then his campaign sorta just flatlined. In the meantime, he ran as the candidate of character and personal biography, not energy, ideas, and hope. And he got crushed as the country went through the crucible of the 2008 financial crisis.

Biden’s not like that. He isn’t a personality-personal-history candidate; he’s a former-vice-president-who-knows-how-the-system-works candidate.

ret: If Biden is going to make himself more relevant to the moment, I think he needs to do more than emphasize his command of bureaucracy or his experience of personal tragedy. He’s going to need to reintroduce voters to the “Scranton Joe” side of his biography. One reason I suspect Trump is benefiting politically from the pandemic is that he’s been talking about minimizing the economic fallout and getting the country back to work

That might be irresponsible from a medical and epidemiological point of view. But it resonates with millions of Americans, especially small business owners and their employees faced with complete financial ruin if the shutdowns carry on for months.

the idea of a much longer nationwide shutdown strikes me as no less dangerous, potentially more so. The economic damage would be monumental, beyond anything in the power of the government to fix. It runs the risk of creating a secondary health crisis in terms of depression, isolation, suicide, addiction and so on.

It doesn’t require, for instance, quickly lifting quarantines based on outlying projections of low fatality rates, as some return-to-normalcy conservatives have been urging in the last week

Rational hope accepts that the situation is genuinely dark, but then it still looks around for signposts leading up and out. It recognizes that things are likely to get worse, but keeps itself alert to the contexts in which they seem to be getting better

three patterns where I’m finding optimism right now.

First, there is modest hope in data compiled by the smart-thermometer company Kinsa, which claims to be able to identify anomalous, unseasonal fever rates using data from its nationwide user base.

Kinsa’s data show a clear February-and-March anomaly across the U.S., especially in areas known to be affected by the coronavirus. But it also shows that anomaly diminishing as lockdowns and social distancing began

the sharp turn suggests that general infection curves can be changed quickly even during a pandemic, and that the policies of the last two weeks might be having a real epidemiological effect.

Second, there is hope in the differing course of the pandemic so far in Greater New York versus the Pacific Coast.

Washington State bent its curve after the initial surge and California’s case rate and death rate trends are a gentle incline — nothing like the New York area’s terrifying spike.

In the most optimistic case, the spike reflects New York’s unique density and heavy reliance on mass transit

maybe some of the divide reflects policy — the fact that West Coast leaders acted ever-so-slightly more swiftly and with more seriousness of purpose than the feckless Bill de Blasio in New York City.

it suggests that even if you initially fail to spot an outbreak, you can still hope to imitate South Korea rather than northern Italy.

the circumstantial evidence of Western versus Asian epidemic curves and the direct evidence of multiple studies suggest that masking works, and that its widespread adoption can change an epidemic’s course.

These three hopeful signs together hint at a path back toward quasi-normalcy. The current shutdown bends infection curves relatively quickly, outside a few major urban outbreaks. That policy response combines with America’s social-distancing sprawl and car culture and younger-than-Europe age profile to compensate for our initial incompetence and natural insubordination. And then the cheapest, lightest-weight means of slowing transmission becomes ubiquitous in U.S. cities by Memorial or Independence Day.

There might be other explanations. With any infection, there are four basic questions to ask when looking at broad differences in death rates. Is the virus different here versus there? NO. Right now, there is no evidence that the virus is mutating toward a more potent strain in the US.Is one country diagnosing the virus sooner than another? YES. As above, this may be skewing German and South Korean results by identifying asymptomatic and mildly symptomatic persons unlikely to require medical care. Hospitalization rates by country, currently not tracked, would help sort out the contribution of aggressive testing to survival rates. Is the infected patient different here versus there? YES. South Korea (young patients) and Italy (old patients) are unique in the outbreak, and the characteristics in Iran are not well known. All other countries with specific information, from China to even the US epicenter of New York City, have shown the same basic distribution with respect to age, sex (more men than women) and smoking. Is the health care system different here versus there? OH YES. Health care system differences at the country level are hard to examine: information is sparse and, given the 50,000-foot view, possibly misleading. However, health care experts typically can rely on "structural measures" to determine the quality of a hospital or a state or a country.

The World Bank tracks health care information by country on three relevant structural measures (though recentness of information varies country to country), each measured per 1,000 general population: doctors, nurses and hospital beds. They and other sources also track two other relevant variables: lifespan per country and health care spending per individual. Neither of these demonstrate differences in affected Western European countries that might explain a difference in Covid-19 survival.

Among the nine countries with the highest number of Covid-19 cases, the country that has the highest nurse rate also has the lowest death rate from the disease. Germany has 13.2 nurses per 1,000 (echoing a trend for high nurse numbers throughout Northern Europe) far above the other heavily Covid-19 affected countries. This may be just another armchair epidemiologist observation of course. But higher numbers of nurses may reflect one of two beneficial factors (or both): first, that nurses, the backbone of hospital (and especially ICU) care, are essential to patient management and, ultimately, survival.

Either way, it is a reminder that Covid-19 will continue to reveal the strengths and weaknesses of health care systems across the world. The current observed differences also mandate that, when we finally are out from underneath the weight of the current crisis, we must work to determine how we can deliver better health care to large populations across the world.

Based on epidemiological projections, as the virus ran unchecked, it would quickly expand to infect somewhat over half the population before herd immunity would slow its course. Assuming a death rate of about 1 percent of those infected, about 1.7 million Americans would die within a year.

The only case in which the benefits of lifting restrictions outweigh the costs in lost lives, Mr. Wolfers said, would be if “the epidemiologists are lying to us about people dying.”

Government agencies calculate these trade-offs regularly. The Environmental Protection Agency, for instance, has established a cost of about $9.5 million per life saved as a benchmark for determining whether to clean up a toxic waste site.

The economy would contract sharply even without a government-imposed lockdown as people chose to stay away from workplaces and stores, hoping to prevent contagion. In that case of voluntary isolation, Mr. Eichenbaum and his colleagues estimated that U.S. consumer demand would decline by $800 billion in 2020, or about 5.5 percent.

It’s useful to adopt the cost-benefit frame, but the moment you do that, the outcomes are so overwhelming that you don’t need to fill in the details to know what to do,”

A policy to contain the virus by reducing economic activity would slow the progression of the virus and reduce the death rate, but it would also impose a greater economic cost.

Mr. Eichenbaum and his colleagues say the “optimal” policy — assessing economic losses alongside lives — requires restrictions that slow the economy substantially. Under their approach, the decline in consumption in 2020 more than doubles, to $1.8 trillion, but the deaths drop by half a million people

That would amount to $2 million in lost economic activity per life saved.

an important corollary is that there are limits to the sacrifice: Beyond a certain point, it would not be worth it to lose more economic activity in order to save more people.

The discussion gets even more touchy when one considers the age profile of the dead. It raises the question: Is saving the life of an 80-year-old as valuable as saving the life of a baby?

Cass Sunstein, a legal scholar who worked for the Obama administration, heading the White House office in charge of these valuations, once proposed focusing government policies on saving years of life rather than lives, as is customary in other countries.

Here is the plain fact: You cannot reconstruct the economy until COVID-19 is under control. Period. Full-stop.

There a number of milestones that need to be passed before we can seriously begin rebuilding the economy: (1) We need to have a clear epidemiological picture of the scope of infection and transmission rates. (2) The healthcare system needs to be in a place where it has the resources to manage the demand load. (3) We need to have the capacity to rapidly test (and immediately process) an hugely elastic number of people.

Once those tasks have been met, we can start to slowly rebuild. To attempt to "restart" the economy before they have been met will give us the worst of both worlds: An out-of-control pandemic plus a ravaged, non-functional economy.

imagine how the economy would function with large numbers of Americans hospitalized; with many others sick; with people afraid for the lives of their loved ones; with some large percentage of children pulled from school; with workers calling out sick for fear of infecting their workplaces; with international travel severely curtailed; with supply chain disruptions across the globe; with demand—especially international demand—decimated.

is 500-some deaths worrisome? I mean, sure, in the sense that every life is precious. But that number isn't what's really scary: What's scary is the curve and were that projects out to 8 days, or 16 days, or 32 days from now

To believe that you can have a robust—or even functional—economy with a pandemic raging in the background is a fantasy. And it's a dangerous fantasy, because acting on that belief will cause both more death and more economic pain.

As of this morning, we have only 46,481 confirmed cases of COVID-19 in the U.S. and 593 deaths

the problem is not the number of cases. It's the rate of increase:

That puts us as 40,000 new cases per day in eight days' time, with a total addition of somewhere in the neighborhood of 180,000 news cases during that period.

Until the new case curve begins to flatten we can't have any sense of what the steady-state looks like.

I've been banging on about this for weeks now, but I want to hammer it again: Where we are today doesn't matter. 

If this is what your case distribution looks like, then you can safely assume that the virus has achieved break-out and is basically everywhere. The places without positive results are most likely just places where tests haven't been available yet.

Until you have control over these curves, any attempt to "restart" the economy will fail because the underlying economic problem—a global pandemic which has the United States in its grip

A second expert agreed broadly. Dr. Arnold Monto, a professor of epidemiology at the University of Michigan School of Public Health, said by email: "I agree that by 3 weeks, we will have a better idea of what is going to happen going forward. The outbreaks seem to be hitting different communities at different times and at different intensities, so it is hard to generalize However, I agree in general. And that is why action now in terms of social distancing is so important."

He said he was more skeptical about the United States being able to lift restrictions on only part of the population. "Asking a subset to remain sheltered in place, to remain in home, that's more difficult to do," he said by phone.

Dr. William Schaffner, an infectious disease specialist at Vanderbilt University, said the peak might take three more weeks.

One disease modeler said it was "impossible to predict" when the peak would hit. Dr. Stefan Flasche, a disease modeler at The London School of Hygiene & Tropical Medicine, told CNN by email the peak was influenced by the efficiency of lockdown measures, and "may be anywhere between some time very soon and not for another few months."

President Donald Trump has said his desire to lift measures as quickly as possible is motivated by a desire to get the American economy moving again. He has expressed a belief that the economy could experience a "v" shaped, ultra-fast recovery. Yet one economist expressed doubt recovery could be that fast-paced and warned that snapping back in and out of restrictions could cause greater damage.

Erin Strumpf, a professor of economics at McGill University, told CNN: "Nothing suggests that we could just 'snap back' to life as it was before. We're taking concrete actions to lower the probability of an uncertain outcome."

Some people clucked over his decision to keep his annual St. Patrick’s Day date with President Trump in Washington during the early days of the outbreak. While there, he called a dramatic news conference at Blair House, opposite the White House, to announce he was closing Irish schools and banning large gatherings.

he compensated for those stumbles with an address on St. Patrick’s Day that was viewed by commentators as one of the most memorable ever delivered by an Irish leader.

while Ireland lags top performers like Iceland and Norway, it has tested at more than double the rate of Britain.

Last month, Ireland got in early in negotiating a €208 million ($226 million) deal with China for this protective gear and scheduled Aer Lingus flights to bring it back. Some of the gowns had been cut for Chinese medics and were too short for Irish doctors. But today Ireland is not suffering from the shortages that afflict other countries

Nor does it have a shortage of ventilators, thanks to a chain of manufacturers.

At the outset of the contagion, Dr. Kearney said, Ireland aggressively tested and traced the contacts of people with symptoms. That quickly stretched its testing capacity, and it was forced to pull back.

Dr. Varadkar’s decision to go back to work as a physician was motivated by a desire to help ease the burden on health care workers, his spokesman said. He also issued a plea for emigrant Irish doctors and nurses, and others who had left the field, to return to help with the surge of patients. So far, 60,000 have responded.

Ireland also moved swiftly to impose social distancing, working off an influenza pandemic plan developed 13 years ago

It called off a major rugby match between Ireland and Italy in late February, an unpopular decision at the time. But now, experts said, people are adhering to Ireland’s lockdown better than those in Britain.

“We’ve all rolled in behind these measures,” Dr. McConkey said. “Even though we’ve had a legacy of shooting at each other over decades, we’re actually quite a socially cohesive society.”