I spent much of yesterday (probably like most people) watching scenes of protests and clashes with police across many America cities. I may have watched it with a slightly different perspective than others. In addition to the messages of outrage and social injustice, I saw a spectrum of protective measures taken against COVID-19 by protesters and law enforcement alike.

We should expect an increase in coronavirus cases in those cities with mass gatherings. You may remember early on in the epidemic that groups of greater than 20 were prohibited. Simply stated, the dynamics of having a large crowd in one place will facilitate the spread of a respiratory virus. Further, people may have traveled from hundreds of miles away to participate in protests, potentially bringing the virus back to a previously unaffected area.

We do know that COVID-19 spreads less readily outdoors The fact that protests occurred outdoors (as opposed to an indoor stadium for example) will exert some protective effect. A study of over 300 transmission clusters in China showed only 1 cluster (of 2 people) with outdoor spread. The remainder were primarily in the home or public transportation. However, the spread outdoors may be modified by usual greater distance between an infected individual and those susceptible to the infection. in cases where protesters were squeezed into a confined space by their own volition or by police action, distancing became simply impossible.

Shouting and singing are modalities by which COVID-19 can spread more readily. Notably religious services (South Korea) and choir practice (Washington State) have been case studies of this phenomenon. But, again, both of these reports were from indoor gatherings, not outdoors.

I saw a wide variety of personal protections being taken by law enforcement. Some police officers had masks, face shields, gloves and long sleeved pants and shirts. Others were wearing T-shirts and no mask or face protection at all. The face shields in particular might function as effective protection against COVID-19. It would be unlikely that respiratory droplets expelled could work their way upwards underneath the shield’s opening.

There was significant geographic variation as well (none of these observations are scientific). In NYC, officers appeared to be more generally protected. Officers in Salt Lake City often had no face coverings whatsoever. I did not see any officers with hand sanitizer (presumably, such would cause them to loosen grip). Officers in Minneapolis were able to disperse crowds from a far distance using a combination of tear gas and flash/bangs leading to little direct contact. In Los Angeles’ Fairfax district and Chicago, police and protestors were essentially engaged in a prolonged shoving matches.

Similarly protesters opted for a range of protection from N95 masks and ski goggles to none whatsoever. Again, this showed a regional variation with those in NYC having more robust personal protection than those in Atlanta, Miami, Chicago and Minneapolis. Also, it is important to remember that face masks get to be very hot and uncomfortable over time (which is a problem for health care workers as well). So as the protests went later and also as the demonstrations became more vigorous, personal protection was shed.

Cases of COVID-19 have been declining dramatically over the past two weeks in Los Angeles County (see graph below). Just in the last week they have dropped from 8.82 daily cases per 100,000 population to 5.22. It will probably be another two weeks before we see any uptick associated with these protests. But hopefully, Los Angeles has enough momentum from shelter-in-place orders to minimize its impact on case numbers.

Lastly, in the chaos and adrenaline of the moment, the public health measures we have been so carefully emphasizing were hard to remember. This became obvious to me after an interview between Los Angeles Police Chief Michel Moore and CNN’s Paul Vercammen. As their emotional interview ended, they did the usual, expected, pre-COVID-19 thing – they shook hands.