Black Lives Matter protests are having a counterintuitive effect on Covid-19 spread

After the murder of George Floyd at the hands of Minnesota police, a socially distanced country erupted into mass protest. Given what we know about how coronavirus spreads, there's been a fear that cases would spike in response to protesting crowds.

But according to a new report, a very different response has happened instead.

Covid-19 cases have not spiked in response to the Black Lives Matter protests, according to a working paper posted Monday by the National Bureau of Economic Research.

This conclusion is based on social distancing data collected in 315 US cities between May 15 and June 13. George Floyd was murdered on May 25, in the middle of that data window. The paper has not been peer-reviewed.

It’s possible that the United States still might see cases rise as protests endure — protests in New York, for example, have been happening for 30 days. To account for more recent data, lead study author Dhaval Dave tells Inverse he has run his analysis again.

“We think three weeks' data is enough – if there was something significant going on it would show up in three weeks of data,” he tells Inverse. “Just recently we ran one extra week of data and our conclusions didn’t change."

“We don’t see any significant uptick of Covid-19 cases in the communities where the protests are happening.”

This suggests that concerns that protests would become “super-spreader events” have not come to pass. Instead, Dave's work indicates that it’s the non-protestors who may be playing a key role by staying home.

Why didn’t cases increase? – This study includes data collected on June 17 and June 18 in Boston from 52 testing sites. Of 17,000 protestors tested for Covid-19, 2.5 percent tested positive. Massachusetts Governor Charlie Baker called those numbers “reasonably consistent” with overall Covid-19 cases in the state. In comparison, in King County, Washington, 5 percent of 1,008 positive coronavirus cases seen over a 19-day period in June were traced back to protests, The Seattle Times reported.

By using anonymized cell phone data to estimate how social distancing behaviors might have changed as protests emerged, this research offers an explanation for why protests may not be linked to increasing cases.

When it came to non-protestors, social distancing actually increased as protests broke out, the analysis suggests.

“If the protests are perceived to be dangerous through violence or clashes with the police you may have individuals choose not to leave their home or go outside. Or if the non-attendees perceive that because of these protests there's a higher risk of contracting Covid-19, these individuals may choose to stay home,” Dave says.

That, the paper argues, may have offset the increased risk facing protestors, creating a net neutral effect of the protests for the whole community.

Will the cases stay down? – The paper suggests that protests have not yet driven Covid-19 cases in the communities where they happen. The question is: How long will that last?

There are a few factors that push and pull that risk:

• The number of people in general that have Covid-19.
• How long that compensatory behavior (non-protestors staying home) persists.

The only way to know for sure if these events will spread Covid-19 among protestors themselves is to know the composition of the crowd — how many protestors have Covid-19 and how many don’t, explains Arni S.R. Srinivasa Rao, the director of Georgia Medical College’s Laboratory for Theory and Mathematic Modeling. (He was not involved in this NBER paper).

In theory, you could base that off how many people within one population are expected to have the coronavirus. If there’s a high proportion of people in a city infected with Covid-19, you might expect more people in the crowd to have coronavirus.

For now, Dave notes that the Covid-19 positive rates of protestors are not “significantly higher than what we see in the average population. For Seattle, D.C., and Boston for instance, the rate is around one or two percent.”

As cases climb in hotspots like Texas, Arizona, California, and Florida, that could change the composition of the crowd.

Even then, you can’t guarantee that those infected will actually turn up to protest. That’s in part because protesting safely means not attending if you feel sick.

“For example, let us consider a high Covid-19 prevalence city, with around 5% of the population infected with COVID-19, and suppose none of the protestors of that city could have the virus," Rao explains. "Then obviously none of the protesters will be spreading among themselves on the day of protests."

For now, it’s impossible to predict how the composition of infected versus susceptible people in the crowd could change, says Rao.

Still, even if the amount of Covid-19 positive people increases, Dave’s analysis suggests that it could be contained by the compensatory behaviors seen in non-protestors, provided they continue to stay home. Between 4 and 7 days after protests begin, there's a two percent increase (relative to the average) of non-protestors staying home.

“We can't conclude very strongly, but the pattern suggests that when the protests are more persistent they tend to increase these compensatory behaviors," Dave says.

The paper also notes that social distancing may “level off or decline” about a week after the protests began. But if protests persist, or reignite, increases in social distancing might reactivate, in turn creating a potential cycle of protesting and compensation by non-protestors.

For now, this work suggests those protesting racial injustices are far from driving a surge of coronavirus cases. But whether that will continue as the country’s first wave of coronavirus picks up speed is still an open question.

Abstract: Sparked by the killing of George Floyd in police custody, the 2020 Black Lives Matter protests have brought a new wave of attention to the issue of inequality within criminal justice. However, many public health officials have warned that mass protests could lead to a reduction in social distancing behavior, spurring a resurgence of COVID-19. This study uses newly collected data on protests in 315 of the largest U.S. cities to estimate the impacts of mass protests on social distancing and COVID-19 case growth. Event-study analyses provide strong evidence that net stay-at-home behavior increased following protest onset, consistent with the hypothesis that non-protesters’ behavior was substantially affected by urban protests. This effect was not fully explained by the imposition of city curfews. Estimated effects were generally larger for persistent protests and those accompanied by media reports of violence. Furthermore, we find no evidence that urban protests reignited COVID-19 case growth during the more than three weeks following protest onset. We conclude that predictions of broad negative public health consequences of Black Lives Matter protests were far too narrowly conceived