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Three Important Ways the COVID Problem Is Incredibly Concentrated

People wear face masks as they wait in line to receive free food at a curbside pantry in the Brooklyn borough of New York City, April 24, 2020. (Mike Segar/Reuters)

A few items that caught my eye these past few days:

First, just before the long weekend, this analysis of the virus’s genetic changes dropped. The results imply that just 1 to 10 percent of carriers cause 80 percent of secondary infections. (You can find a lot more research in a similar vein here.) This means we should think a lot more about “superspreading,” in terms both of superspreading events and of superspreading people.

Superspreading events tend to be situations where lots of adults come into close contact with each other for prolonged periods indoors, often talking or singing loudly. In such a situation, one infected person can pass the virus to many others at once. If superspreading is a big part of how this virus spreads in general, we need to be very careful about these situations. On the flip side, we might be a little less uptight about other interactions, where contacts are brief or outdoors, though masks and safe distances are still good when convenient.

Another possible contributor to the study’s result is superspreading individuals. Maybe there’s some reason these folks expel the virus more, or maybe — owing to their jobs or what have you — they are just more likely to find themselves in the dangerous situations outlined above. The latter types of superspreaders could actually be good news: People with lots of close contacts were probably more likely to get the virus early and gain some immunity, meaning that the most prolific spreaders might be taken out of commission for future waves, and that “herd immunity” could come at a lower threshold than we previously expected.

Second: We already knew that the elderly were far more vulnerable to COVID-19 than the young, and of course that viruses spread more easily in close quarters. Add those together and it’s clear nursing homes are at serious risk. But Avik Roy has managed to put some numbers on the problem: Nursing homes and assisted-living facilities hold just 0.6 percent of the population but have produced 43 percent of COVID deaths in the U.S. 

It is very difficult to completely isolate these places, because care workers need to go home for the night and family members want to visit. But as we reopen, nursing homes must be a high priority for testing, temperature checks, and the like. Most important, any nursing-home resident, worker, or visitor found to have COVID-19 must be removed or securely isolated immediately.

Third: Pew got some flak for this dumbly worded tweet, but I think the chart is important. Blue (largely urban) areas were hit harder than red (more rural) areas, but the epidemic seems to be fading more slowly in the latter. These dynamics have both political and epidemiological ramifications we should want to sort out.

Mark Perry made a similar point this week about the severe damage to several dense urban areas, and the lighter toll elsewhere in the country (so far). One-third of U.S. COVID deaths are in counties that hold just 4 percent of the population, and another third are in counties holding 11 percent. As I’ve urged before, we obviously need to have different policies in different places.


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