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What Scientist Do And Don't Know About The Spread Of The Coronavirus

MARY LOUISE KELLY, HOST:

One point seven million cases, more than 100,000 deaths.

UNIDENTIFIED PERSON #1: Albert Farber (ph). Albert Bernard (ph). Albert Fields, Jr. (ph).

KELLY: People in all 50 states.

UNIDENTIFIED PERSON #2: Evelyn Moore (ph). Evelyn Sanchez (ph).

KELLY: All ages.

UNIDENTIFIED PERSON #3: Shirley Birnesser. Shirley Fine.

KELLY: All walks of life.

UNIDENTIFIED PERSON #3: Ali Dennis Guillermo.

KELLY: So how did we get to this point in America? And short of a vaccine, how do we change course? We're going to consider those questions in this next part of the program, and consider how much we still don't know a little over four months since the first reported case of coronavirus in this country.

BEN ALTHOUSE: Everything has been blowing us away in kind of a perfect storm with this virus.

KELLY: Ben Althouse is a mathematical epidemiologist with the Institute For Disease Modeling - one of the scientists we called who is working furiously to figure out why the virus spreads where it does. Also, who transmits the virus and why. He says compared with the flu, the coronavirus has proven to be much more random in how it spreads, more random in how one sick person might infect others around them. Scientists, including Althouse, now believe just 10% or 20% of cases lead to 80% or 90% of the spread.

ALTHOUSE: You think about flu, where one person may give rise to one or two people on average and that's pretty consistent. But then if you think about COVID, most people give rise to zero infections - maybe one, but then all of a sudden you'll get a person that gives rise to 10, 15, 100. That's what we consider the randomness, and we call those the superspreading events.

KELLY: What is a perfect superspreader event? What is the worst-case scenario?

ALTHOUSE: The worst-case scenario is - so for example, the Washington state choir outbreak. You have a room with, say, one infected individual. Everyone around them is susceptible, and they're out there belting, singing, moving lots of air. There is virus in droplets that come out of your mouth. And that's the perfect storm. And, in fact, most people in that choir got infected.

KELLY: Sure did - 53 out of 61 who attended the 2 1/2-hour rehearsal, according to the CDC. Two people died. And turns out, that choir in Skagit County, Wash., was not the only one.

GWEN KNIGHT: Something that we're looking into is the relatively high number of choirs that we have seen come through. So a couple in the U.S., couple in Germany. Possible one in the U.K.

KELLY: Gwen Knight and her colleagues at the London School of Hygiene and Tropical Medicine are working on a global database of clusters of coronavirus cases. They want to figure out which settings are riskiest for transmission and why. So far, there are some tantalizing clues, but still many questions, in part, because outside of Asia there hasn't been a whole lot of contact tracing.

KNIGHT: We don't really have a systematic idea of where and when transmission has occurred.

KELLY: Now, we do know all signs point to indoor settings as more risky. Think of the outbreaks on cruise ships, in nursing homes, in worker dormitories and at funerals and other religious gatherings. But Knight says there are settings she is surprised haven't been virus hot spots - at least that we know of - places like the playing fields of full-contact sports.

KNIGHT: What I am interested in is the fact that we haven't seen many local sports teams, for example. Like, rugby teams, for example. It hasn't popped up apart from choirs.

KELLY: And do we know why?

KNIGHT: I don't think they yet. But one thing may be that they're spending time outdoors. It could be that we're just not seeing them because they haven't been detected so we don't have good enough contact tracing. Or it could be that it's less risky than singing together. But it's really not clear.

KELLY: So many unknowns. Here's one more. Why of all the factories all over the world - why do America's meatpacking plants seem to be such hot spots?

(SOUNDBITE OF MONTAGE)

UNIDENTIFIED REPORTER #1: Tyson has announced that they will temporarily pause production at their pork plant in Storm Lake, Iowa. Good evening, everyone.

UNIDENTIFIED REPORTER #2: More troubles at Colorado's largest meatpacking plant. Dozens of workers sick...

UNIDENTIFIED REPORTER #3: Production lines have become coronavirus hot spots. Here in North Carolina, nearly 500 workers...

KELLY: Nationwide, nearly 20,000 meatpacking workers have been infected in 33 states. That's according to the Midwest Center for Investigative Reporting. At least 69 have died. We do know meatpacking plants are cold to keep the meat cold and viruses thrive in chilly temperatures. Again, Gwen Knight.

KNIGHT: I know that that has come up as one of the hypotheses that it's because they're cold. It could also be because they're loud.

KELLY: So people might have to shout to be heard.

KNIGHT: And also, long shifts. I think it's interesting as well that these places have come up. And once they start to come up, then it becomes a bit of a spiral because then you start looking there because you know that that's a setting that transmission has occurred. And I wonder if we're not seeing it in other settings because we just haven't looked.

KELLY: And, in fact, there are now produce farms in the U.S. reporting outbreaks.

I mean, it sounds like there are still way more questions than answers as we roll into June and half a year of this.

KNIGHT: Definitely. I think it's going to be very interesting, from an epidemiological point of view, now, to see what settings pop up unfortunately linked in more clusters as we go forward.

KELLY: More clusters because as states reopen and people squint and blink and return to public spaces, might opportunities for superspreader events be returning, too?

(CROSSTALK)

KELLY: Memorial Day weekend - the unofficial start of summer - brought out crowds not seen in months. This video shows revelers packed in a pool at the Lake of the Ozarks in Missouri. It sparked outrage, and then outrage at the outrage. This, my friend, is called freedom and liberty. It's called constitutional rights, tweeted one woman, who said she was there. I asked Ben Althouse of the Institute for Disease Modeling what he thought.

As someone who studies this stuff, what went through your head when you saw some of those pictures and videos of people standing shoulder-to-shoulder in pools, in lakes, over the Memorial Day weekend?

ALTHOUSE: I was - yeah, I was disappointed. I was disheartened. You know, as epidemiologists, we work really hard to study how these viruses transmit. And now that we have a bit of knowledge about how it is transmitted and how transmissible it is and contagious, it really was disappointing to me. And it just brings home the message that we need to think carefully about this. I've seen the numbers. I've seen that social distancing works.

KELLY: So do we know to what extent the way that things unfolded - the way the virus spread this spring - to what extent that will predict how things may unfold this summer as the country reopens and people start to emerge from their homes?

ALTHOUSE: Right. Well it's hard to predict about the future. In terms of warm weather, there has been some speculation that we'll catch a break and the warm weather will tamp down some of the transmission, but we don't know for sure. It's being transmitted across the globe across a range of seasons right now, so we may not get a break in summer.

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KELLY: One more set of numbers to keep in mind - as of now, new cases of the coronavirus are rising in just over a dozen states. They're falling in a few more than that. And the remaining states say their number of new infections is holding more or less steady. As the virus continues to circulate, so do questions about how it spreads, how to protect ourselves and our loved ones and how to balance risk with our desire to reopen the economy and rejoin life in full swing. Transcript provided by NPR, Copyright NPR.