Question: I thought this article, “K: This Overlooked Variable Is Key to the Pandemic,” was really insightful about our approach to the pandemic. I guess the question is, what are your thoughts on what this might look like in practice (here in the US)?

Answer: Thanks for sharing the article from The Atlantic. I also thought it was insightful. For those of you who haven’t read it, here are the main points (but the article is way more informative and interesting, so please read it!):

• Instead of spreading in a steady manner (like seasonal flu), SARS-CoV-2 spreads in bursts, where one person infects many (e.g. superspreading events). Enter ‘k’, a measure of dispersion. COVID-19 is overdispersed. Its “highly skewed, imbalanced distribution means that an early run of bad luck with a few super-spreading events, or clusters, can produce dramatically different outcomes even for otherwise similar countries.”
• To stop the spread of COVID-19, we have to focus on superspreading events — focus attention on the cluster bursts rather than the individual infections. [Note: the author points out that super-spreading events overwhelmingly occur in poorly ventilated indoors environments with many people over an extended period of time, especially where there is loud talking or singing. Sound familiar? It’s the same set of conditions as the airborne transmission risks we talked about yesterday!
• Recognizing the nature of COVID-19 transmission, we need to adapt our response:
• Target potential clusters. Keep prohibitions on crowded, indoor events. Mandate mask wearing indoors.
• Refocus contact tracing. Right now, if you’re positive, contact tracers will generally focus on finding everyone you interacted with in the previous 2 weeks to warn them and ask them to test and self-isolate (prospective tracing). Instead, contact tracing should focus on finding who infected you and then trace forward all of their contacts (retrospective tracing). In doing so, contact tracers are more likely to find positive people and stop the cluster from blossoming.
• Focus on rapid, cheap tests. For clustering, overdispersed transmission, speed is more important than accuracy. Instead of focusing testing on more accurate, but more time consuming PCR tests, we should make widespread use of rapid tests. These rapid tests will let us identify cluster events (more important than identifying infected individuals); the moment we suspect a cluster event, we can then use more precise testing while asking those who were at the event to self-isolate.
• Use wastewater testing. Like a canary in the coal mine, wastewater testing can give us a signal that either there are likely no infections or that there is a potential cluster, in which case we need to ask folks, especially in congregant settings, to self-isolate and test.

In the United States, I think the big switch in our approach would be this switch to “cluster busting.” This means that our focus would need to shift to preventing, detecting, and mitigating collective risks/transmission events, rather than individual-level risks/transmission events approach we currently take. The bullets above describe what this approach would look like. We’d need to have more standardized guidance to limit indoor, crowded events and mandate mask wearing, particularly indoors. We’d need to increasingly rely on rapid tests and wastewater testing and take swift action as soon as we get the signal from such tests of a potential cluster. And, we’d need to refocus contact tracing efforts on identifying where a cluster event took place and finding everyone at that event to ask them to test and self-isolate to keep the virus from spreading.