In study after study, we see that super-spreading clusters of COVID-19 almost overwhelmingly occur in poorly ventilated, indoor environments where many people congregate over time—weddings, churches, choirs, gyms, funerals, restaurants, and such—especially when there is loud talking or singing without masks. For super-spreading events to occur, multiple things have to be happening at the same time, and the risk is not equal in every setting and activity, Muge Cevik, a clinical lecturer in infectious diseases and medical virology at the University of St. Andrews and a co-author of a recent
extensive review of transmission conditions for COVID-19, told me.
...
Because of overdispersion, most people will have been infected by someone who also infected other people, because only a small percentage of people infect many at a time, whereas most infect zero or maybe one person. As Adam Kucharski, an epidemiologist and the author of the book
The Rules of Contagion, explained to me, if we can use retrospective [backwards] contact tracing to find the person who infected our patient, and
then trace the forward contacts of the infecting person, we are generally going to find
a lot more cases compared with forward-tracing contacts of the infected patient, which will merely identify
potential exposures, many of which will not happen anyway, because most transmission chains die out on their own.
...
Meanwhile,
researchers have shown that rapid tests that are very accurate for identifying people who do
not have the disease, but not as good at identifying infected individuals, can help us contain this pandemic. As Dylan Morris, a doctoral candidate in ecology and evolutionary biology at Princeton, told me, cheap, low-sensitivity tests can help mitigate a pandemic even if it is not overdispersed, but they are particularly valuable for cluster identification during an overdispersed one. This is especially helpful because some of these tests can be administered via saliva and other less-invasive methods, and be distributed outside medical facilities.
for example there were some very bad cholera outbreaks at the same time.
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