How superspreading is fueling the pandemic — and how we can stop it
“On average, people with the coronavirus infect about two other people; most pass the virus to just one other person, or to no one else at all.
But some people go on to infect many more — often before they even get symptoms. Many of these transmission chains begin with superspreading events, where one person (usually in a crowded indoor space) passes the virus to dozens of others. Early contact tracing studies suggest these events have been a large driver of transmission around the world. By some estimates, 10 percent of people have been causing 80 percent of new infections.”
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“To understand what might kick off a superspreading event, let’s review some basics about how this virus, SARS-CoV-2, spreads. Researchers have found that it often spreads through microscopic droplets created when an infected person coughs or sneezes — or even speaks — and another person breathes them in. These disease-containing droplets are a large part of the reasoning behind staying at least 6 feet away from people and wearing a mask in public.
But scientists are finding that the virus likely also spreads through even tinier, longer-lasting particles from breathing or speaking (or flushing a toilet) called aerosols. These are so small they can linger in the air after an infectious person has left — and may contain infectious virus particles for up to three hours. And they may be a key element to superspreading events: An infected person could seed a poorly ventilated indoor space with virus without even getting physically close to all the people they end up infecting.
Superspreading also appears to be more likely with SARS-CoV-2 because people typically have the highest level of the virus in their system (making them infectious) right before they develop symptoms. (This is very different from other severe coronaviruses like SARS and MERS, where people were most infectious seven to 10 days after they started feeling sick, when they were more likely to be in isolation or in medical care.) So thousands of people with active Covid-19 infections continue to go about their lives not knowing that they could be spreading the disease.”
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“Some individuals seem to develop higher amounts of the virus in their system, upping their odds of transmitting it to others.
And given that the amount of virus in the body tends to shift over the duration of infection — rising until around the onset of symptoms, then declining — the chance that someone is a likely superspreader changes over time.”