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Since the emergence of coronavirus disease 2019 (COVID-19), unprecedented movement restrictions and social distancing measures have been implemented worldwide. The socioeconomic repercussions have fueled calls to lift these measures. In the absence of population-wide restrictions, isolation of infected individuals is key to curtailing transmission. However, the effectiveness of symptom-based isolation in preventing a resurgence depends on the extent of presymptomatic and asymptomatic transmission. We evaluate the contribution of presymptomatic and asymptomatic transmission based on recent individual-level data regarding infectiousness prior to symptom onset and the asymptomatic proportion among all infections. We found that the majority of incidences may be attributable to silent transmission from a combination of the presymptomatic stage and asymptomatic infections. Consequently, even if all symptomatic cases are isolated, a vast outbreak may nonetheless unfold. We further quantified the effect of isolating silent infections in addition to symptomatic cases, finding that over one-third of silent infections must be isolated to suppress a future outbreak below 1% of the population. Our results indicate that symptom-based isolation must be supplemented by rapid contact tracing and testing that identifies asymptomatic and presymptomatic cases, in order to safely lift current restrictions and minimize the risk of resurgence.

There is a need to better understand the contribution of asymptomatic SARS-CoV-2 infections (those with no symptoms at all throughout the infection) in driving the current pandemic. However, there are caveats that in our opinion are pertinent when interpreting the reported findings of this review, including the lack of a clear definition of asymptomatic infection and selective inclusion of cross-sectional studies. In addition, there is a problematic interpretation of a narrative review containing a dearth of poor-quality evidence resulting in an overestimate of asymptomatic infections, which might misinform policy response.

Among the many uncertainties that remain about Covid-19 is how the human immune system responds to infection and what that means for the spread of the disease. Immunity after any infection can range from lifelong and complete to nearly nonexistent. So far, however, only the first glimmers of data are available about immunity to SARS-CoV-2, the coronavirus that causes Covid-19.

Antigen tests don't amplify their protein signal, so they are inherently less sensitive. To make matters worse, that signal gets diluted when samples are mixed with the liquid needed to enable the material to flow across test strips. As a result, most antigen tests have a sensitivity of anywhere between 50% and 90%-in other words, one in two infected people might incorrectly be told they don't have the virus. Last month, Spanish health authorities returned thousands of SARS-CoV-2 antigen tests to the Chinese firm Shengzhen Bioeasy Biotechnology after finding the tests correctly identified infected people only 30% of the time, according to a report by the Spanish newspaper El Pais.

Aerosol transmission of viruses must be acknowledged as a key factor leading to the spread of infectious respiratory diseases. Evidence suggests that SARS-CoV-2 is silently spreading in aerosols exhaled by highly contagious infected individuals with no symptoms. Owing to their smaller size, aerosols may lead to higher severity of COVID-19 because virus-containing aerosols penetrate more deeply into the lungs (10). It is essential that control measures be introduced to reduce aerosol transmission. A multidisciplinary approach is needed to address a wide range of factors that lead to the production and airborne transmission of respiratory viruses, including the minimum virus titer required to cause COVID-19; viral load emitted as a function of droplet size before, during, and after infection; viability of the virus indoors and outdoors; mechanisms of transmission; airborne concentrations; and spatial patterns. More studies of the filtering efficiency of different types of masks are also needed. COVID-19 has inspired research that is already leading to a better understanding of the importance of airborne transmission of respiratory disease.

Ehre, a member of the UNC Marsico Lung Institute and the UNC Children's Research Institute, captured these images to illustrate how intense the SARS-CoV-2 infection of the airways can be in very graphic and easily understood images. Her lab conducted this research in collaboration with the labs of Ralph Baric, Ph.D., the William R. Kenan Distinguished Professor of Epidemiology at the UNC Gillings School of Public Health, who holds a joint faculty appointment at the UNC Department of Microbiology and Immunology, and Richard Boucher, MD, the James C. Moeser Eminent Distinguished Professor of Medicine and Director of the Marsico Lung Institute at the UNC School of Medicine Covid-19

Bart Haagmans (Erasmus MC) concludes: "The observations made in this study provide definite proof that SARS-CoV-2 can multiply in cells of the gastrointestinal tract. However, we don't yet know whether SARS-CoV-2, present in the intestines of COVID-19 patients, plays a significant role in transmission. Our findings indicate that we should look into this possibility more closely." The current study is in line with other recent studies that identified gastrointestinal symptoms in a large fraction of COVID-19 patients and virus in the stool of patients free of respiratory symptoms. Special attention may be needed for those patients with gastrointestinal symptoms. More extensive testing using not only nose and throat swabs, but also rectal swabs or stool samples may thus be needed.

" Fearless commentary on finance, economics, politics and power Follow yvessmith on Twitter Feedburner RSS Feed RSS Feed for Comments Subscribe via Email SUBSCRIBE Recent Items Links 3/11/17 - 03/11/2017 - Yves Smith Deutsche Bank Tries to Stay Alive - 03/11/2017 - Yves Smith John Helmer: Australian Government Trips Up Ukrainian Court Claim of MH17 as Terrorism - 03/11/2017 - Yves Smith 2:00PM Water Cooler 3/10/2017 - 03/10/2017 - Lambert Strether Why a 400-Year Program of Modernist Thinking is Exploding - 03/10/2017 - Yves Smith Links 3/10/17 - 03/10/2017 - Yves Smith Why It Will Take a Lot More Than a Smartphone to Get the Sharing Economy Started - 03/10/2017 - Yves Smith CalPERS' General Counsel Railroads Board on Fiduciary Counsel Selection - 03/10/2017 - Yves Smith Another Somalian Famine - 03/10/2017 - Yves Smith Trade now with TradeStation - Highest rated for frequent traders Why a 400-Year Program of Modernist Thinking is Exploding Posted on March 10, 2017 by Yves Smith By Lynn Parramore, Senior Research Analyst at the Institute for New Economic Thinking. Originally published at the Institute for New Economic Thinking website Across the globe, a collective freak-out spanning the whole political system is picking up steam with every new "surprise" election, rush of tormented souls across borders, and tweet from the star of America's great unreality show, Donald Trump. But what exactly is the force that seems to be pushing us towards Armageddon? Is it capitalism gone wild? Globalization? Political corruption? Techno-nightmares? Rajani Kanth, a political economist, social thinker, and poet, goes beyond any of these explanations for the answer. In his view, what's throwing most of us off kilter - whether we think of ourselves as on the left or right, capitalist or socialist -was birthed 400 years ago during the period of the Enlightenment. It's a set of assumptions, a particular way of looking at the world that pushed out previous modes o

A sweeping effort to map a hospital's microorganisms has found that infectious pathogens hide in a place that's all about cleaning: the sink. Niranjan Nagarajan at the Genome Institute of Singapore and his colleagues sampled bacteria from bed rails, sinks and other sites in a Singapore hospital. Microbes that tend to grow in slimy 'biofilms' and cause hospital-acquired infections were prevalent on sink traps and faucet aerators, whereas skin-dwelling bacteria were abundant on objects, such as door knobs and bed rails, that are often touched. Frequently touched sites harboured multidrug-resistant microbes such as methicillin-resistant Staphylococcus aureus, which might persist in the hospital environment for more than eight years, the team suggested.

A new machine-learning framework uses reported test results and death rates to calculate estimates of the actual number of current COVID-19 infections within all 50 U.S. states and 50 countries. Jungsik Noh and Gaudenz Danuser of the University of Texas Southwestern Medical Center present these findings in the open-access journal PLOS ONE on February 8,