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Experts focus on ‘superspreaders’ to study virus transmission

As businesses reopen and cases across several states in the U.S. and across the world surge, experts worry that “superspreaders,” a small percentage of infected people are transmitting the virus to a much larger percent, could be fueling the pandemic. Hari Sreenivasan speaks with Ben Lopman, an epidemiology professor at Emory University’s Rollins School of Public Health, about the transmission data he and his team are studying.

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  • Hari Sreenivasan:

    One of the concerns of COVID-19, is the ability for a small percentage of infected people to spread the disease to a much larger percent. They are known as "superspreaders."

    And with businesses reopening and more summer gatherings taking place, experts worry that superspreader events will only increase the transmission of the virus.

    I recently spoke with Ben Lopman, professor of epidemiology at Emory University's Rollins School of Public Health about the data he and his team are studying.

    What did you and your team go out to study?

  • Ben Lopman:

    We wanted to study how transmission is occurring in our state in Georgia. We worked with the data collected by the Georgia Department of Public Health and we examined who is who is transmitting this disease and how many people are going on to infect.

  • Hari Sreenivasan:

    And what did you find?

  • Ben Lopman:

    Our main finding is that we found evidence of superspreading. Superspreading is where one person or one event goes on to infect many more people than the typical infectious person.

    We use surveillance data that are collected by the local and the state public health departments. They ask people their age, they ask them where they were when when they their symptoms began. And we use that kind of bread and butter surveillance data, do some statistical studies.

    And in those studies, in that analysis, we found this evidence that some some people or some events are much more important in terms of transmission. In a rural county where we did our work there was a report of a couple of funeral events where there were many documented cases that occurred also in slaughterhouses in the north of the state and nursing homes around our state and has been reported very widely around the country, for that matter.

  • Hari Sreenivasan:

    And when you're able to get this statistical data, is this based on, for example, location from cell phones or stuff that's publicly available where you can see clusters of people gathering?

  • Ben Lopman:

    We don't use individuals cell phone data. However, we did incorporate information on on mobility, not directly on the people who were infected, but how people were moving from county to county, for example. And that was part of the data that helped us to understand how transmission was occurring.

  • Hari Sreenivasan:

    Right now, the article is in preprint for someone who doesn't follow how academic journals work. What does that mean?

  • Ben Lopman:

    That means that our research has not yet been peer-reviewed. And that's an important point. We have a team of investigators that haven't been involved in this research. And we've also been working with our collaborators, for example, with the Georgia Department of Public Health. We've all been scientifically critical of our work.

    This pandemic is obviously moving very fast and academic peer review can be a lengthy process. And so we felt it was important that this information get out there while peer-review is ongoing.

  • Hari Sreenivasan:

    And so when you see these superspreader events, is there any kind of demographic data that you can figure out from there saying, hey, it looks like it's people from this group that are doing it and they're going to have ripple effects on these other demographics?

  • Ben Lopman:

    This is one of the really important findings of our research, is that we've found that younger people, and that's a pretty big category in our work, people under the age of 60, were more important in terms of transmission than older people.

    Now we know that older people bear the burden of this disease. But what we found is that younger people are more important in terms of transmission. So targeting that younger group to stop transmission is probably more important in terms of controlling the epidemic. And it also gives me concern.

    We are seeing now in many states reporting that the age of of cases is is younger than it was early on in the epidemic. And so while that might be good in terms of severe disease, it's worrying, in terms of transmission.

  • Hari Sreenivasan:

    What's the implication here? I mean, how do you translate your findings into policy that leaders should be looking at?

  • Ben Lopman:

    Now, that's very important. You know, this this term superspreading or superspreading events, it sounds ominous, but actually, in terms of public health, it gives us a hook of something that we can actually do.

    We know, for example, that large gatherings are really important in terms of these kinds of events. And so if we target our public health messages there, if we encourage people to not be part of large events, to not go to large events, we can have a bigger impact in terms of curtailing transmission.

  • Hari Sreenivasan:

    Was there anything that surprised you when you looked at all this data?

  • Ben Lopman:

    One thing that was encouraging actually was in the very beginning of the epidemic in Georgia, people were going on to infect, on average, about three people. And then as people started to social distance and the lock-in orders were put in place in our state that number dropped to less than one, which is the number we have we are targeting to keep transmission under control for the epidemic to be declining. So I think one of the important results of our study is that those interventions had a really big effect on transmission.

  • Hari Sreenivasan:

    All right, Ben Lopman, professor of epidemiology from Emory University. Thanks so much for joining us.

  • Ben Lopman:

    My pleasure. Thank you.

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