COVID-19: What we’ve learned

A new meta-analysis of COVID studies shows how the virus spreads and what we can do to avoid it.

There have been no lack of studies of COVID-19 since the novel coronavirus that causes it emerged as a worldwide pathogen early this year. A new meta-analysis conducted by virologists from the U.K. looked at almost 100 of these studies to tease out what we know about the virus and how people can avoid it.

The researchers, including Dr. Müge Çevik of the U.K.’s New and Emerging Respiratory Virus Threats Advisory Group, drew from research published since 2003 on the virus behind COVID-19 as well as those that caused the SARS and MERS epidemics earlier this century. All are coronaviruses.

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What did they find? Some important things that could affect how we respond to the current pandemic.

Indoor Spread: The riskiest place to be is indoors with a group of people.

Early on in the pandemic scientists thought every interaction with a potentially infected person was equally risky, according to Çevik. It turns out that spending time indoors with a group of people in a small space is far more conducive to transmitting infection than any other activity.

“There are some studies showing that just opening a window decreases the risk of infection,” said Çevik in an interview with the BBC’s Science Focus.

Handwashing: While washing your hands is important, it pales in comparison to the risk of spending time indoors with others. Again, ventilation is important. Opening a window allows air to circulate and limits the risk of infection.

Clusters: Çevik said that COVID-19 spreads in clusters, but contact tracing practices have yet to catch up with this methodology.

Currently, contact tracing efforts focus on tracking every individual who has tested positive for the coronavirus. Instead, contact tracers should focus on environments where multiple people may have been infected in one situation.

“Most people will have been infected by someone who also infected other people, often at the same time. That means we need to backwards contact – trace those people to identify the settings of transmission,” said Çevik.

Asymptomatic Transmission: People who haven’t yet developed symptoms of COVID-19 aren’t the biggest cause of the spread of the virus.

Data shows that only about 20% of transmission of the coronavirus comes from asymptomatic people. While still a large number, people showing symptoms seem to be far more likely to spread the virus.

Çevik said that the cluster approach to contact tracing could also be useful for testing regimens. He points to Japan, which is focusing its testing protocols on large groups and high risk environments.

“One of the epidemiologists from Japan says that their approach is like looking at a forest and trying to find the clusters, not the trees,” she said. “And he thinks that the Western world is getting distracted by the trees and got a little lost.”

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