Scientists suggest most people with the coronavirus aren’t contagious

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Most of the spread appears to come in large groups

The longer the coronavirus (COVID-19) pandemic goes on, the more scientists studying the virus learn new things about it. Many of these new things overturn previous assumptions.

For example, an early assumption was that the coronavirus was highly contagious. It is, scientists say, but only from a small number of people who get it, not from the majority who get sick.

A recent article in Science magazine cites data from the Centers for Disease Control and Prevention (CDC) and interviews with researchers that suggest most of the cases of COVID-19 can be traced to so-called “superspreader events,” where 30 or more people are gathered in an enclosed space.

Researchers at the London School of Hygiene & Tropical Medicine (LSHTM) linked an outbreak in a migrant worker dormitory in Singapore to almost 800 cases. The gatherings don’t have to be huge to become superspreader events. 

Live music locations in Osaka, Japan are believed to have contributed to as many as 80 infections, and 65 cases are linked to Zumba classes in South Korea. The scientists say that’s why there have been so many outbreaks at nursing homes, ski resorts, prisons, hospitals, and churches.

Social distancing and avoiding large groups

The takeaway from this latest research suggests policies of social distancing and canceling sporting events that attract arenas full of people may have kept the toll from the virus from being even worse. At the same time, the scientists interviewed for the article say other restrictions might be eased.

“If you can predict what circumstances are giving rise to these events, the math shows you can really, very quickly curtail the ability of the disease to spread,” UCLA’s Jamie Lloyd-Smith told the magazine.

The study of the disease’s spread has led scientists to a rather startling conclusion. A few people with the virus appear to give it to nearly everyone they come in contact with. Others don’t spread it at all. Adam Kucharski, a scientist at LSHTM, estimates that about 10 percent of COVID-19 cases lead to 80 percent of the spread.

Beyond advising people to avoid being in large groups, the researchers say their efforts are aimed at being better able to predict the risk of infection. In doing so, they say mitigation efforts can be more precisely targeted and not shut down wide swaths of the economy.

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