Attention to the Unseen

A few people in the crowd will be responsible for the bulk of a disease’s spread. Pacific Press /LightRocket via Getty Images Elizabeth McGraw, Pennsylvania State University The coronavirus has traveled the globe, infecting one person at a time. Some sick people might not spread the virus much further, but some people infected with the SARS-CoV-2 are what epidemiologists call “superspreaders.” Elizabeth McGraw, the director of the Center for Infectious Disease Dynamics at Pennsylvania State University, explains the evidence and…

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Ars Technica reports: Much about how the new coronavirus spreads from one victim to the next remains a maddening mystery. But amid all the frantic efforts to understand transmission, there is one finding that appears consistent: that it is inconsistent. Some people—most, even—don’t spread the virus to anyone in the course of their infection. Others infect dozens at a time. It’s a phenomenon that looked, at first, like anomalous anecdotes—a large outbreak from a Washington choir practice, a South Korean…

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SFGate reports: We’ve all heard it many times: Wear a face covering — indoors, outdoors, on trains and buses. At work, in the supermarket and at church. But now a new modeling study out of Cambridge and Greenwich universities suggests that face masks may be even more important than originally thought in preventing future outbreaks of the new coronavirus. To ward off resurgences, the reproduction number for the virus (the average number of people who will contract it from one…

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CNBC reports: Coronavirus patients without symptoms aren’t driving the spread of the virus, World Health Organization officials said Monday, casting doubt on concerns by some researchers that the disease could be difficult to contain due to asymptomatic infections. Some people, particularly young and otherwise healthy individuals, who are infected by the coronavirus never develop symptoms or only develop mild symptoms. Others might not develop symptoms until days after they were actually infected. Preliminary evidence from the earliest outbreaks indicated that…

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The Washington Post reports: Shutdown orders prevented about 60 million novel coronavirus infections in the United States and 285 million in China, according to a research study published Monday that examined how stay-at-home orders and other restrictions limited the spread of the contagion. A separate study from epidemiologists at Imperial College London estimated the shutdowns saved about 3.1 million lives in 11 European countries, including 500,000 in the United Kingdom, and dropped infection rates by an average of 82 percent,…

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The Canadian Press reports: Masks and social distancing can help control the coronavirus but hand washing and other measures are still needed, a new study from Hamilton’s McMaster University says. Researchers concluded single-layer cloth masks are less effective than surgical masks, while tight-fitting N95 masks provide the best protection. A distance of 1 metre (more than 3 feet) between people lowers the danger of catching the virus, while 2 metres (about 6 1/2 feet) is even better. Eye protection such…

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Helen Branswell writes: New research has poured cold water on the theory that the Covid-19 outbreak in Washington state — the country’s first — was triggered by the very first confirmed case of the infection in the country. Instead, it suggests the person who ignited the first chain of sustained transmission in the United States probably returned to the country in mid-February, a month later. The work adds to evidence that the United States missed opportunities to stop the SARS-CoV-2…

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Science reports: On 9 March, a patient who had recently traveled to Europe and had symptoms of COVID-19 visited the emergency department of St Augustine’s, a private hospital in Durban, South Africa. Eight weeks later, 39 patients and 80 staff linked to the hospital had been infected, and 15 patients had died—fully half the death toll in KwaZulu-Natal province at that time. Now, scientists at the University of KwaZulu-Natal have published a detailed reconstruction of how the virus spread from…

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Ian Sample reports: Earlier this week, England’s deputy chief medical officer Jonathan Van-Tam said the words nobody wanted to hear: “We can’t be sure we will get a vaccine.” But he was right to be circumspect. Vaccines are simple in principle but complex in practice. The ideal vaccine protects against infection, prevents its spread, and does so safely. But none of this is easily achieved, as vaccine timelines show. More than 30 years after scientists isolated HIV, the virus that…

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