201 - Overdispersion of COVID-19: Why A Small Percentage of People May Be Responsible for the Majority of Transmission
Public Health On Call
The Johns Hopkins Bloomberg School of Public Health
4.6 • 644 Ratings
🗓️ 13 November 2020
⏱️ 12 minutes
🧾️ Download transcript
Summary
High profile instances show up in the news as "super spreader" events, but there's evidence that the phenomenon of "overdispersion" could be much more common. Infectious disease epidemiologist Dr. Justin Lessler and doctoral student Kyra Grantz talk with Dr. Josh Sharfstein about the biological and social contributors to overdispersion, and what it could mean for public health strategy.
KEYWORDS: pandemic response; contact tracing; viral shedding
Transcript
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| 0:00.0 | Welcome to Season 2 of Public Health On Call, a podcast from the Johns Hopkins Bloomberg School of Public Health. |
| 0:13.6 | I'm Joshua Sharfstein, Vice Dean for Public Health Practice and Community Engagement, |
| 0:18.7 | and a former secretary of Maryland's Health Department. |
| 0:21.9 | Our goal is to bring scientific evidence and experience to the public health news of the day |
| 0:27.3 | through informative interviews with scientists, community leaders, policy experts, public health |
| 0:32.7 | officials, clinicians, and more. If you have ideas or questions for us to cover, please email us at |
| 0:39.8 | Public Health Question at jhhhu.edu. That's public health question at jhhu.edu for future podcast |
| 0:47.8 | episodes. Today, I speak to two infectious disease epidemiologists at Johns Hopkins about the concept of over dispersion, |
| 0:57.3 | the idea that maybe 10 or 20% of people with COVID |
| 1:01.0 | are responsible for a large share of the diseases spread. |
| 1:04.5 | What's the evidence for over dispersion? |
| 1:06.9 | And what does it mean for how we can respond? |
| 1:09.2 | Joining me is Dr. Justin Lusler and Kira Grants, a doctoral student at the school. |
| 1:15.0 | Let's listen. |
| 1:16.6 | So Kira, thanks so much for joining me. |
| 1:19.4 | And I want to start with a question. |
| 1:21.5 | Can you explain over-dispersion? |
| 1:23.7 | Sure. |
| 1:24.2 | And thank you for having us to talk about this. |
| 1:26.7 | So over-dispersion is actually not something specific to infectious diseases. It's more of a statistical phenomenon. But it just means that you have a lot of variability in your population. And in infectious diseases, that normally manifests as this idea that a small proportion of people are responsible for a very |
| 1:46.4 | large proportion of transmission. And so for COVID-19 or SARS-Co2, the virus, we think that about |
| 1:53.5 | 10% of people are responsible for about 80% of transmission, which means that it's highly over-dispersed. |
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