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The US Centers for Disease Control and Prevention says building immunity to Covid-19 "typically takes a few weeks" after vaccination and that it's possible a person could be infected before or after being vaccinated

CNN reported earlier this week that Correa was accosted by President Donald Trump supporters at Dulles International Airport following the Pro-Trump insurrection at the Capitol.

The situation has caused concern in places struggling to secure enough vaccine supply, principally in Europe.

Dr. Byrne and her colleagues measured risky decision-making by presenting people with a gambling scenario. They could choose between two bets: One offered a guaranteed amount of money, while the other offered the possibility of a larger amount of money but also the possibility of receiving no cash. A different exercise measured people’s preference for immediate versus delayed rewards: Participants could choose a certain amount of money now, or a larger amount later.

Study subjects also reported Covid-19 precautions they had taken in their daily lives, including masking and social distancing.

with Covid-19, people don’t feel sick immediately after an exposure so the benefits of wearing a mask, social distancing or getting vaccinated aren’t immediately apparent. “You don’t see the lives you potentially save,” she says

“People generally are more motivated by immediate gratification or immediate benefits rather than long-term benefits, even when the long-term benefits are much greater,

Research has also found being extroverted or introverted affects how people make decisions about Covid-19 precautions. A recent study of more than 8,500 people in Japan published in the journal PLOS One in October 2020 found that those who scored high on a scale of extraversion were 7% less likely to wear masks in public and avoid large gatherings, among other precautions.

The study also found that people who scored high on a measure of conscientiousness—valuing hard work and achievement—were 31% more likely to follow Covid-19 public-health precautions.

Scientists believe that a person’s propensity to take risks is partly genetic and partly the result of early life experiences

Certain negative childhood experiences including physical, emotional or sexual abuse, parental divorce, or living with someone who was depressed or abused drugs or alcohol are linked to risky behavior in adulthood like smoking and drinking heavily, other research has found.

Studies of twins have generally found that about 30% of the difference in individual risk tolerance is genetic

And scientists have discovered that the brains of people who are more willing to take risks look different than those of people who are more cautious.

ambling task had differences in the structure and function of the amygdala, a part of the brain involved in detecting threats, and the prefrontal cortex, a region involved in executive

Even people who have the same information and a similar perception of the risks may make different decisions because of the ways they interpret the information. When public-health officials talk about breakthrough infections in vaccinated individuals being rare, for example, “rare means different things” to different people

An outbreak isn’t a double pendulum; it’s much more convoluted. Myriad chains of events, operating in overlapping networks, conspire to chart its course.

It’s the double pendulum, and as a physical object, it’s very simple: A pendulum (a string and a weight) is attached to the bottom of another. Its movement is explained by the laws of motion written by Isaac Newton hundreds of years ago.

But slight changes in the initial condition of the pendulum — say it starts its swing from a little higher up, or if the weight of the pendulum balls is a little heavier, or one of the pendulum arms is a bit longer than the other — lead to wildly different outcomes that are very hard to predict.

The double pendulum is chaotic because the motion of the first pendulum influences the motion of the second, which then influences the entire apparatus. There isn’t a simple scale or ratio to describe how the inputs relate to the outputs. A one-gram change to the weight of a pendulum ball can result in a very different swing pattern than a two-gram change.

It teaches us to understand the mechanics of a system — the science of how it works — without being able to precisely predict its future. It helps us visualize how something that seems like it should be linear and predictable just isn’t.

That’s why, when pressed, epidemiologists have to say they don’t know what’s going to happen.

Climate scientists clearly tell us adding CO2 to the air will increase global temperatures. Yet they argue about when the worst effects of climate change will be felt and how bad it will be

Still, they know the mechanics of outbreaks. The chaos “doesn’t necessarily mean we know nothing,” Kissler says. They understand the conditions that make an outbreak worse and the conditions that make it better.

There is a tough tension of the current moment that we all need to work through: The future is clouded in chaos, but we know the mechanics of this system

Here are the mechanics. Scientists know that if we let up on social distancing, without an alternative plan in place, the virus can infect more people. They know this virus is likely to persist for at least a few years without a vaccine. They know it’s very contagious. That it’s very deadly. They also know that its pandemic potential is hardly spent, and that most of the population of the United States and the world is still vulnerable to it.

Will residents keep up with mask-wearing and social distancing, even when their leaders relax regulations? Plus, there are scientific questions about the virus still not understood: Will it diminish transmission in a seasonal pattern? Do children contribute greatly to its spread? How long does immunity last after an infection? Why do some people breathe out more of the virus than others? The answers to these questions will influence the future, and we do not know the answers.

Scientists are still unraveling what makes the difference between a sprawling outbreak in one city and a more manageable one in another. Some of it is the result of policy, some is the result of demographics, some is about structural inequality and racism, and some comes down to individual behavior. Some of it is just luck. That’s chaos for you.

“I don’t see uncertainty as a lack of knowledge,” says Philipp Lorenz-Spreen, a physicist who studies the chaos of a different sort of viral dynamics. “I think it’s a fundamental part of how our world works. It’s not our fault we do not know where this all will go.”

Newton clearly told us what happens when an object drops from the sky. But follow his laws, and find that the path of a double pendulum is very, very difficult to predict.

There’s a simple mechanism that is helping me understand the many possible futures we face with the Covid-19 pandemic.

Epidemiologists are clearly telling us what happens when you bring masses of people together during a pandemic. But they can’t tell us the exact shape this outbreak will take.

With Germany set for a four-day-weekend in early April due to the Easter holiday, Spahn said the country isn't ready to relax travel and physical distancing rules. In fact, he said, Germans should be prepared to revert to tighter restrictions.

"Health experts are calling on the German government to order a third lockdown to prevent hospitals from being overrun," NPR's Rob Schmitz reports from Berlin.

As it tries to boost its vaccine campaign, Germany is also moving ahead with talks to acquire Russia's Sputnik V vaccine — with or without the rest of the EU's involvement.

Spahn said Friday that he believes a deal with Russia could be reached quickly once a delivery amount is agreed upon.

He is doing so, he said, partly based on new science, and partly on his gut feeling that the country is finally ready to hear what he really thinks.

Now that some polls are showing that many more Americans are ready, even eager, for vaccines, he said he felt he could deliver the tough message that the return to normal might take longer than anticipated.

We really don’t know what the real number is. I think the real range is somewhere between 70 to 90 percent.

not sure there will be enough voluntary acceptance of vaccines to reach that goal.

They also came with a warning: All answers are merely “guesstimates.”

Humans move around, so studying disease spread among them is far harder.

It took about two months to be certain that there were many asymptomatic people who had also spread the virus.

The more transmissible a pathogen, the more people must become immune in order to stop it.

Dr. Dean noted that to stop transmission in a crowded city like New York, more people would have to achieve immunity than would be necessary in a less crowded place like Montana.

If we can vaccinate almost all the people who are most at risk of severe outcomes, then this would become a milder disease.”

Sorrentino said the study defined economic impact by the extent that a city's economy was closed -- businesses like restaurants, gyms, salons and airports that would lose business without people's physical presence.

The study took into account both the costs associated with quarantining (which requires supervision costs as well as costs due to lowered productivity) as well as social distancing (which incurs costs only due to productivity).

"But our model shows that even before we achieve herd immunity, we can relax social distancing compared to the situation prior to immunization."

The analysis looked at Seattle, beginning on December 14, 2020, when the vaccine was first being administered. Even with this limited data, the effect of vaccinations was dramatic, impacting the so-called "optimal control solution."

While the optimal interventions would vary depending on a number of factors, we always saw that a gradual relaxation of social distancing was possible after roughly 10% of the population got vaccinated," he said.

After just 20 days, the trend was becoming clear when comparing with the case in which the effects of vaccinations were not incorporated in the model.

Sorrentino emphasizes also that everyone should continue to follow the current policy and health guidelines, and that the relaxing of social distancing should adhere to these guidelines and be gradual. And of course, that guidance may change, based on the rates of spread of the virus and the variants.

But one piece of advice almost no one is giving? Be lucky. Pediatrician Neil Stone says that there’s no “secret” for staying Covid-19 free because there’s just too much luck involved.

As for me, I have some data that can, to an extent, quantify and explain my own good luck in avoiding Covid so far. I’m participating in a study on immunity which allowed me to learn that my blood still carries loads of antibodies induced by my vaccine and December booster shot, and no signs of any prior infection. Not everyone’s antibodies wane at the same rate, and in some people, the antibodies don’t wane much at all. (At some point it should become routine to collect this information to help people decide whether to get additional booster shots.)

My high level of vaccine antibodies probably explains my success more than my behavior. I make some effort to avoid Covid, but have been far from perfect. And I’ve been potentially exposed at least twice: Once last December, when someone at a small holiday gathering I’d attended developed symptoms the next day, and more recently, when I shared a large indoor space with two people who later tested positive. But according to my lab work, I’ve never had even a silent infection.

It’s possible I was protected by my high antibodies, or that some quirk of air flow meant I never breathed in enough virus to get sick. Or perhaps I benefited from a different form of luck. There’s another facet to immunity called the innate immune system, which acts as a first line of defense and sometimes knocks out a virus or other pathogen before it replicates enough to elicit the production of antibodies. Good innate immunity might help explain something many of us have experienced — not getting a cold or flu even when sleeping in the same bed with the sick person through the whole illness.

Stress, diet, general health and even sunlight might all affect innate immunity. So could other factors. There’s so much we still don’t know about the immune system. And that’s one reason we talk about “luck.”

understanding how the luck works could help other people avoid Covid, whether for the first time or for the second or third time. Taking a closer look at what passed for luck helped researchers like Gary Taubes discover that public health had obesity all wrong, and the standard high carb/low fat diets were causing people to gain weight.

On the domestic front, travelers arriving in the U.S. from the U.K. are now required to show proof of a negative COVID-19 test under new rules issued by CDC on Christmas day.

Despite such measures, the new strain has already been detected in mainland Europe, Israel, Canada and Japan, among other places.

compared to Hong Kong, which has put in place a "prohibition of group gatherings of more than two persons."

While some other places are shortening COVID quarantines from 14 days down to 10 or 7, Hong Kong is now requiring a mandatory 21 days.

Thailand, which had kept its daily tally of reported COVID-19 cases in the single digits for much of the pandemic, is grappling with its worst surge to date.

South Korea, which successfully contained two earlier waves of COVID-19, is facing record numbers of new cases and a spike in fatalities.

Given the high levels of transmission already occurring in the U.S., a more transmissible form of the virus could mean more even more dire numbers just as massive vaccine campaigns are starting.

“One of the things that we are feeling better about is the data around SARS-CoV-2 transmission and recognizing that outdoor activities have not turned out, as best as we can tell, to be a significant factor in pushing the pandemic forward,” Brewer said, referring to the fact that the threat of virus spread is low in socially distant, outdoor settings

People who are vaccinated can also spend time indoors with unvaccinated, low-risk people from a single household.

“If you look at what’s happening with cases in particular, they’ve really fallen off since the beginning of January,” Brewer said. “It’s really hard to attribute that to population changes; something else has to be driving that. It couldn’t have been vaccines at that point, we didn’t have as many vaccines as we do now.”

“I continue to look for signals and continue to scrutinize the data, but so far I’m encouraged by the fact that we haven’t seen a real rise in case numbers particularly in the states where they have reported the variants,” said Nuzzo, who has been tracking COVID-19 trends and data since the pandemic’s beginning.

Much of the old nomenclature has turned out to be not only stigmatizing but inaccurate. The Ebola virus, for instance, gets its name from a river that sits about forty miles from Yambuku, the Congolese village where researchers first investigated the disease, in 1976.

Still, it’s hard not to see a similarity between the recent reports of harassment against Asian-Americans and the stigmatization that gay people suffered in the wake of the AIDS outbreak.

Evolutionary psychologists refer to a “behavioral immune system” that attunes humans to physical differences or unfamiliar behavior, even when it poses no risk.

Last week, an Asian-American journalist reported that a member of the President’s staff called COVID-19 the “kung flu” to her face.

This may seem like a trivial issue to some, but disease names really do matter to the people who are directly affected

no disease better illustrates the perils of disease naming than AIDS, which, in its early days, was sometimes called “gay cancer.”

No test is perfectly accurate; all generate false positives and false negatives. How many varies by the test — the new Abbott Labs test, for example, has a false negative rate of about 3 percent and a false positive rate of about 1.5 percent.

We’d also require public understanding that test results are a risk-assessment tool rather than a definitive answer. And shifting the public’s thinking might be harder than shifting Trump.

Doing that would also require fundamentally changing our thinking.

For mass testing to work, people will need to understand that even an event where all attendees just tested negative isn’t necessarily covid-free, because some false negatives might have slipped through

Giving hundreds of millions of citizens this crash course in elementary statistics would be very difficult. Teaching people how to think about a positive result would be even harder — especially if mass testing does its job of reducing caseloads. Because as case numbers fall, false positives will become a bigger and bigger problem.

Say we’re testing 200 people, 10 of whom have covid-19. Given its rate of false negatives, the Abbott test would probably catch all 10. But with false positives, it could also tell one or two people who don’t have covid-19 that they’re infected. That’s not ideal — as good citizens, they’d have to go home and quarantine. But a more sensitive follow-up test could substantially mitigate this problem, shortening such quarantines to a day or so. It would be worth it to get those 10 true positives out of circulation.

Doing this, we might eventually reduce the share of the population that’s infected to, say, 0.5 percent from 5 percent. Unfortunately, the false positive rate won’t budge, so now for every one true positive uncovered, roughly three false positives would still be generated.

That’s inherently costly: Every false positive means skipping your flight, rehearsal or birthday party. But it would be catastrophic if people didn’t understand that a positive covid-19 test is a guideline, not a guarantee

People who think that they’ve had covid-19, when they haven’t, are apt to go out and engage in risky behavior, maybe a lot of it. And if mass testing ever becomes common, there could be a lot of those people.

So mass testing isn’t just a matter of getting a test that is cheap enough and plentiful enough; the administration and the public must be educated to use this bounty wisely. That’s a hard messaging problem. Given the alternative, though, it’s the kind of problem we’d really like to have.

“Since older people are also more likely to experience severe disease symptoms and, sadly, die, our findings make clear how important it is to implement policies to protect the elderly during the pandemic,

The large new study out of Denmark did not examine the role of variants in reinfection, given the time frame of the research. So it does not offer any clues about whether variants make it more likely for someone to come down with COVID-19 more than once.

The Centers for Disease Control and Prevention recommends that people who have had COVID-19 should get vaccinated once it’s available to them, in large part because there is a slim chance they could become infected again if they come into contact with the virus.

Screens, small and large, became crucial links to the rest of the world.

In doing so, they rediscovered each other, and experienced the joys of bonding and the suffocation of constant proximity.

In some instances, these revelations were not happy ones: lawyers and mediators saw a spike in clients looking to divorce as soon as courts reopened.

Engagements and pregnancy announcements seemed to pop up constantly on social media. And there were plenty of weddings.

Couples in quarantine learned a lot about their significant others.

Inside nursing homes, Covid-19 outbreaks became all too regular, with more than 163,000 residents and workers dying of the virus.

In one study, almost one-third of the teens interviewed said they had felt unhappy or depressed.

Parents, especially mothers, left the work force quickly and in large numbers in the spring.

Those who continued working had to balance the demands of their jobs with domestic chores, child care and online schooling, putting strain on their mental health.

Retirees put off plans that had been years in the making, like travel and volunteer work.

Young people around the world, cut off from their usual social lives, faced a “mental health pandemic.”

Delivery drivers dealt with health risks, theft and assault.

Airline workers who weren’t furloughed had to confront passengers who refused to wear masks.

hospital staff around the country dealt with the gut-wrenching horrors of a steep surge in cases.

Doctors and nurses agonized over putting their families at risk, and dealt with intense burnout and pay cuts.

Some said that being characterized as heroes by the public left them little room to express vulnerability.

a toll higher than in any other country.

The world’s struggle to contain the coronavirus was often compared to a war

in this case, the enemy claimed more Americans than World War I, World War II and the Vietnam War combined

Grief and loss defined the last year

Funerals and final goodbyes took place over video calls, if at all.

a sign that people will soon be finding their way back to each other.

If you’re wondering what comes after, we are, too.Are you anxious that things will never be the same? Or are you fearful that we’ll return to “the same” much too quickly? Or maybe there is something seemingly small that you will cherish being able to do?

In the early months of the pandemic, the economic downturn in low- and middle-income countries was almost certainly worse than any other recent global economic crisis that we know of, whether the Asian financial crisis of the late 1990s, the Great Recession that started in 2008, or the more recent Ebola crisis,

The pandemic has produced some hopeful innovations, including a partnership between the government of Togo in West Africa and UC Berkeley's Center for Effective Global Action (CEGA) on a system to provide relief payments via digital networks.

The new study -- the first of its kind globally -- reports that after two decades of growth in many low- and middle-income countries, the economic crisis resulting from the COVID-19 pandemic threatens profound long-term impact: Reduced childhood nutrition could have health consequences later in life.

The study was launched in spring 2020, as China, Europe and the U.S. led global efforts to check spread of the virus through ambitious lockdowns of business, schools and transit. Three independent research teams, including CEGA, joined to conduct surveys in the countries where they already worked.

"COVID-19 and its economic shock present a stark threat to residents of low- and middle-income countries -- where most of the world's population resides -- which lack the social safety nets that exist in rich countries,

Reports early in the pandemic suggested that developing countries might be less vulnerable because their populations are so much younger than those in Europe and North America.

In Colombia, 87% of respondents nationwide reported lost income in the early phase of the pandemic. Such losses were reported by more than 80% of people nationwide in Rwanda and Ghana.

In the Philippines, 77% of respondents nationwide said they faced difficulty purchasing food because stores were closed, transport was shut down or food supplies were inadequate. Similar reports came from 68% of Colombians and 64% of respondents in Sierra Leone; rates were similar for some communities within other countries.

Food insecurity rose sharply.

: In Bangladesh, 69% of landless agricultural households reported that they were forced to eat less, along with 48% of households in rural Kenya

Between April and early July 2020, they connected with 30,000 households, including over 100,000 people, in nine countries with a combined population of 500 million: Burkina Faso, Ghana, Kenya, Rwanda and Sierra Leone in Africa; Bangladesh, Nepal and the Philippines in Asia; and Colombia in South America. The surveys were conducted by telephone.

The evidence we've collected shows dire economic consequences ... which, if left unchecked, could thrust millions of vulnerable households into poverty."

In North America and Europe, nations may be struggling with vaccination plans, but vaccines have barely arrived in most low-income countries, he said

If we can spread the wealth in terms of pandemic relief assistance and vaccine distribution, we're all going to get out of this hole faster."

The state of California is also reporting staggering numbers with more than 2.9 million confirmed cases, according to NBC News counts. Texas, with 2 million cases, and Florida, with 1.5 million, are the next two states with the most infections. New York, which was one of the country’s first and biggest hot spots, has recorded 1.2 million cases to date.

But its faster spread will lead to more cases overall, the study authors wrote, "exacerbating the burden on an already strained health care system, and resulting in more deaths."

Since then, rates have increased by 1,000 percent and have disproportionately affected Latinos, who comprise roughly half of the total population.

It will take a number of months to reach the level of vaccination needed in the population to curb ongoing transmission of the virus."

The pandemic’s descent from medical emergency to political flash point can be mapped as a series of surges of bickering over that one simple phrase. “Follow the science!” people on both sides insisted, as the guidance from politicians and public health officials shifted over the past two years from anti-mask to pro-mask to “keep on masking” to more refined recommendations about which masks to wear and now to a spotty lifting of mandates.

demands that the other side “follow the science” are often a complete rejection of another person’s cultural and political identity: “It’s not just people believing the scientific research that they agree with. It’s that in this extreme polarization we live with, we totally discredit ideas because of who holds them.

“I’m struggling as much as anyone else,” she said. “Our job as informed citizens in the pandemic is to be like judges and synthesize information from both sides, but with the extreme polarization, nobody really trusts each other enough to know how to judge their information.

Many people end up putting their trust in some subset of the celebrity scientists they see online or on TV. “Follow the science” often means “follow the scientists” — a distinction that offers insight into why there’s so much division over how to cope with the virus,

although a slim majority of Americans they surveyed don’t believe that “scientists adjust their findings to get the answers they want,” 31 percent do believe scientists cook the books and another 16 percent were unsure.

Those who mistrust scientists were vastly less likely to be worried about getting covid-19 — and more likely to be supporters of former president Donald Trump,

A person’s beliefs about scientists’ integrity “is the strongest and most consistent predictor of views about … the threats from covid-19,”

When a large minority of Americans believe scientists’ conclusions are determined by their own opinions, that demonstrates a widespread “misunderstanding of scientific methods, uncertainty, and the incremental nature of scientific inquiry,” the sociologists concluded.

Americans’ confidence in science has declined in recent decades, especially among Republicans, according to Gallup polls

The survey found last year that 64 percent of Americans said they had “a great deal” or “quite a lot” of confidence in science, down from 70 percent who said that back in 1975

Confidence in science jumped among Democrats, from 67 percent in the earlier poll to 79 percent last year, while Republicans’ confidence cratered during the same period from 72 percent to 45 percent.

The fact that both sides want to be on the side of “science” “bespeaks tremendous confidence or admiration for a thing called ‘science,’ ”

Even in this time of rising mistrust, everybody wants to have the experts on their side.

That’s been true in American debates regarding science for many years

Four decades ago, when arguments about climate change were fairly new, people who rejected the idea looked at studies showing a connection between burning coal and acid rain and dubbed them “junk science.” The “real” science, those critics said, showed otherwise.

“Even though the motive was to reject a scientific consensus, there was still a valorization of expertise,”

“Even people who took a horse dewormer when they got covid-19 were quick to note that the drug was created by a Nobel laureate,” he said. “Almost no one says they’re anti-science.”

“There isn’t a thing called ‘the science.’ There are multiple sciences with active disagreements with each other. Science isn’t static.”

The problem is that the phrase has become more a political slogan than a commitment to neutral inquiry, “which bespeaks tremendous ignorance about what science is,”

t scientists and laypeople alike are often guilty of presenting science as a monolithic statement of fact, rather than an ever-evolving search for evidence to support theories,

while scientists are trained to be comfortable with uncertainty, a pandemic that has killed and sickened millions has made many people eager for definitive solutions.

“I just wish when people say ‘follow the science,’ it’s not the end of what they say, but the beginning, followed by ‘and here’s the evidence,’

As much as political leaders may pledge to “follow the science,” they answer to constituents who want answers and progress, so the temptation is to overpromise.

It’s never easy to follow the science, many scientists warn, because people’s behaviors are shaped as much by fear, folklore and fake science as by well-vetted studies or evidence-based government guidance.

“Science cannot always overcome fear,”

Some of the states with the lowest covid case rates and highest vaccination rates nonetheless kept many students in remote learning for the longest time, a phenomenon she attributed to “letting fear dominate our narrative.”

“That’s been true of the history of science for a long time,” Gandhi said. “As much as we try to be rigorous about fact, science is always subject to the political biases of the time.”

A study published in September indicates that people who trust in science are actually more likely to believe fake scientific findings and to want to spread those falsehoods

The study, reported in the Journal of Experimental Social Psychology, found that trusting in science did not give people the tools they need to understand that the scientific method leads not to definitive answers, but to ever-evolving theories about how the world works.

Rather, people need to understand how the scientific method works, so they can ask good questions about studies.

Trust in science alone doesn’t arm people against misinformation,

Overloaded with news about studies and predictions about the virus’s future, many people just tune out the information flow,

That winding route is what science generally looks like, Swann said, so people who are frustrated and eager for solid answers are often drawn into dangerous “wells of misinformation, and they don’t even realize it,” she said. “If you were told something every day by people you trusted, you might believe it, too.”

With no consensus about how and when the pandemic might end, or about which public health measures to impose and how long to keep them in force, following the science seems like an invitation to a very winding, even circular path.

SEIR models start to fall apart when you think about the underlying causes of the data. You need models that can allow for all possible states, and assess which ones matter for shaping the pandemic’s trajectory over time.

These techniques have enjoyed enormous success ever since they moved out of physics. They’ve been running your iPhone and nuclear power stations for a long time. In my field, neurobiology, we call the approach dynamic causal modelling (DCM). We can’t see brain states directly, but we can infer them given brain imaging data

Epidemiologists currently tackle the inference problem by number-crunching on a huge scale, making use of high-performance computers. Imagine you want to simulate an outbreak in Scotland. Using conventional approaches, this would take you a day or longer with today’s computing resources. And that’s just to simulate one model or hypothesis – one set of parameters and one set of starting conditions.

Using DCM, you can do the same thing in a minute. That allows you to score different hypotheses quickly and easily, and so to home in sooner on the best one.

This is like dark matter in the universe: we can’t see it, but we know it must be there to account for what we can see. Knowing it exists is useful for our preparations for any second wave, because it suggests that targeted testing of those at high risk of exposure to Covid-19 might be a better approach than non-selective testing of the whole population.

Our response as individuals – and as a society – becomes part of the epidemiological process, part of one big self-organising, self-monitoring system. That means it is possible to predict not only numbers of cases and deaths in the future, but also societal and institutional responses – and to attach precise dates to those predictions.

How well have your predictions been borne out in this first wave of infections?For London, we predicted that hospital admissions would peak on 5 April, deaths would peak five days later, and critical care unit occupancy would not exceed capacity – meaning the Nightingale hospitals would not be required. We also predicted that improvements would be seen in the capital by 8 May that might allow social distancing measures to be relaxed – which they were in the prime minister’s announcement on 10 May. To date our predictions have been accurate to within a day or two, so there is a predictive validity to our models that the conventional ones lack.

What do your models say about the risk of a second wave?The models support the idea that what happens in the next few weeks is not going to have a great impact in terms of triggering a rebound – because the population is protected to some extent by immunity acquired during the first wave. The real worry is that a second wave could erupt some months down the line when that immunity wears off.

the important message is that we have a window of opportunity now, to get test-and-trace protocols in place ahead of that putative second wave. If these are implemented coherently, we could potentially defer that wave beyond a time horizon where treatments or a vaccine become available, in a way that we weren’t able to before the first one.

We’ve been comparing the UK and Germany to try to explain the comparatively low fatality rates in Germany. The answers are sometimes counterintuitive. For example, it looks as if the low German fatality rate is not due to their superior testing capacity, but rather to the fact that the average German is less likely to get infected and die than the average Brit. Why? There are various possible explanations, but one that looks increasingly likely is that Germany has more immunological “dark matter” – people who are impervious to infection, perhaps because they are geographically isolated or have some kind of natural resistance

Any other advantages?Yes. With conventional SEIR models, interventions and surveillance are something you add to the model – tweaks or perturbations – so that you can see their effect on morbidity and mortality. But with a generative model these things are built into the model itself, along with everything else that matters.

Are generative models the future of disease modelling?That’s a question for the epidemiologists – they’re the experts. But I would be very surprised if at least some part of the epidemiological community didn’t become more committed to this approach in future, given the impact that Feynman’s ideas have had in so many other disciplines.

Makeshift morgues have been set up across the state, ICUs are full, oxygen is being rationed and ambulance teams have been told not to transport those unlikely to survive the night because hospitals are too full.

Disneyland, which has been closed since March, is now being turned into a massive vaccination centre

And like most places, Covid-19 has hit Los Angeles' poor the hardest.

For every case of Covid in Beverly Hills, there are six times more in Compton. While two people from Bel Air have died, more than 230 people have lost their lives in working-class East LA.

As the virus spreads, it's likely mutating more than we know, says Dr Neha Nanda."Maybe the bigger the place, the more variation," she says.