On concerns about the spread of COVID-19 at protests

We're worried about the possible increase in spread of the virus when you see people that are congregating together closely and with variable adherence to recommendations like face masking, physical distancing. So we're worried about that. I want to point out that we actually did produce a guidance document that was done not officially through the University California system or through our campuses, but as public health academics. We felt it was important to get a message out, to try to improve the safety and decrease the risk of spread for people that are participating in civil protesting. 

On the recommendation that protesters wear goggles

The recommendations about wearing goggles really are to protect against tear gas and pepper spray. I realized these are deterrents, non-lethal deterrents, that the police have used. And we're not saying that they shouldn't be doing that. We're not trying to make a comment on that. But one of the problems is if people are exposed to tear gas, for example, natural reaction is to put your hands to your face and to your eyes. And so that's a risk factor for picking up the virus. 

On the recommendation to avoid loud chanting, singing

Now there's emerging evidence that loud talking, singing, these are things that increase the risk of transmission of the virus. And of course, these were brought up in the context of religious gatherings and so on. But there's evidence emerging now that there's a higher risk of transmission engaging those activities. So we wanted to at least cover that in our recommendations for people to be thinking about that and perhaps to express themselves in ways other than loud speaking, singing, chanting or screaming. 

On the use of face masks

We think they're better than nothing for sure. There are debates about how effective they are, but the primary reason for wearing the face masks are really to prevent you from potentially spreading it to other people if you are infected. That's the major role that they play. And this is, again, we're not talking about N95 masks worn correctly, where there is actually protection for the person wearing the mask. But this is really a way of trying to reduce the spread to other people. That's the reason for that. And there's been a lot of work done now to look at the types of face mask and materials used, what kinds of cloth, how porous is it? But I think that the recommendations are that certainly covering your mouth and nose in public with these coverings is going to likely have some impact on reducing spread. 

On African-American communities being disproportionately affected by COVID-19

There is very clear evidence in our country that communities of color, the African American community in particular, has been severely impacted. And this may be mostly related to the existence of co-morbidities. The major co-morbidities I'm talking about are heart disease, hypertension, diabetes and obesity. And there is a disproportionate prevalence of those conditions in the African-American community. And so this is just adding to that which we don't need to have. It's not right to be able to have to have folks live through this extra risk. 

And with regard to Mr. Floyd being positive [Editor's note: George Floyd was found to be positive with COVID-19 after his death], there is an example, again, of somebody who wasn't symptomatic but is walking around. And so you just don't know. And that's why we try to think about this as taking universal precautions. You don't know if the person next to you is capable of shedding the virus and transmitting it. And so that's why we've been so effective at doing the social distancing, is that we basically lower our risk of being exposed by keeping that physical distance. And that's really the rationale for this and why California has been so successful relative to other parts of the country at trying to bend the curve.

This interview has been edited for brevity and clarity. Click the “play” button to listen to the entire interview.