It’s been an honor to serve and learn as a member of the COVID-19 Sports and Society Working Group, co-chaired by ex-Obama healthcare head Andy Slavitt and the VP of Basketball Performance for NBA Minnesota Timberwolves Dr. Robby Sikka.
The guys and I wrote down some key takeaways from the different COVID-19 prevention and testing protocols implemented by major league sports in 2020, now published as a paper in The Journal of Bone and Joint Surgery. Here’s the tl;dr:
- Basketball and Hockey: isolation and frequency of testing
- Soccer: shortening time to test result, protocol enforcement, and mask spotters
- Baseball: risks of travel and flying
- Football: scheduling, screening, and high-risk populations
What frequent testing made possible
My favorite* of all the leagues, the NBA, should be incredibly proud of the prevention safety and testing protocols that resulted in 0 cases among players. People were paying close attention to life in the bubble at Disney World. This video below shows the daily testing process, which collected both saliva and nasal swab specimens for testing.
The saliva specimens were used by my brilliant friends at Yale, Anne Wyllie and Nate Grubaugh, to develop the SalivaDirect testing protocol that was granted an emergency use authorization by the Food and Drug Administration in August.
Viral dynamics revealed
That daily testing of players and staff also generated gorgeous real world data to describe the viral dynamics of SARS-CoV-2 infection (Kissler et al). Look at that heterogeneity below! It means that people are really unique and virus replication looks different in every person.
An important thing I learned here is that after an exposure and infection, a lot of people won’t test positive until day 3. That sucks because it’s also the day you’re probably the most contagious and not showing symptoms yet.
This data also changed my thinking about the infectiousness vs share of infections that are attributed to symptomatic vs asymptomatic cases. My current theory is that asymptomatic, pre-symptomatic, and symptomatic people can be equally infectious but the duration of infectiousness is longer for people who show symptoms.
Check out the figure below. It shows the length of days with acute infection is shorter for people without symptoms (blue) compared to people with symptoms (red).
Peak Ct and infection stage duration distributions according to symptoms reported at time of diagnosis (Kissler et al)
We could test out this theory comparing the probability of transmission from a single infectious exposure to results from a household transmission study. Living with a symptomatic person, you would have more exposures because it drags on longer. The evidence might point to higher cumulative probability of transmission from a symptomatic housemate compared to asymptomatic because living together facilitates repeated exposure. Bad causal inference assumes the explanation is that people who never show symptoms are less infectious. My hypothesis is that people never showing symptoms are infectious for a shorter duration of time. Per unit of virus exposure the probability of transmission is probably the same regardless of symptoms, especially around days 3-5. But if the cumulative number of infectious exposures is higher, then it’s more likely one of those aerosolized coronaviruses will successfully make its way into your lungs, past your mucus membranes, bind to an ACE2 receptor, and infect a cell.
The key takeaway for epidemiologists and biostatisticians is that we are short on time. More studies of transmission risk factors should try using time-to-event analysis, such as a Cox proportional hazards models, or other methods to keep the aspect of time in every function.
*The NBA is my favorite because of their early and serious public health leadership during the pandemic.
Even more fun
To end in a happy place, I’ll leave you with a favorite comfort food video to demonstrate some of the impressive logistics inside the NBA bubble. Watching will be way more fun than reading our lessons learned about testing.
See also these washing machines.
Acknowledgements
Huge thanks to the leadership of Robby Sikka and to the COVID Sports and Society Working Group for including me as part of the team.
Photo credit: Jesse D Garrabrant, National Basketball Association, Getty Images