When mass protests erupted nationwide in response to the death of George Floyd in Minneapolis, some epidemiologists expected a surge of transmission of the new coronavirus—but experts say that, so far, there's little evidence to tie the protests to new outbreaks.

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Experts find little connection between protests and coronavirus case surges 

In many cities that saw mass demonstrations, cases of the new coronavirus have continued to decline.

In New York, for example, around 754 cases of Covid-19 were diagnosed on May 27, the day before protests began in the city, according to the city's Department of Health. At the end of the first week of protests, the city saw just over 500 cases a day, and the following week, case counts were around 400, the New York Times reports.

Since then, case counts have continued to drop and haven't risen above 300 since June 23.

"We've been looking very closely at the number of positive cases every day to see if there is an uptick in context of the protests," Ted Long, executive director of New York's contact tracing program, said. "We have not seen that."

Similarly, in Minneapolis, where the protests started, cases of the new coronavirus have steadily declined over the past month, the Washington Post reports. According to the Minneapolis Department of Health, health systems in the area have tested thousands of people who attended protests and have seen less than 1% test positive for the new coronavirus.

Doug Schultz, a spokesperson for the state's Department of Health, said that of the more than 15,000 tests conducted at centers the city established in communities where protests occurred, 1.7% came back positive—well below the statewide average of about 3.6%.

Meanwhile, in Seattle, Portland, Oregon, and Oakland, California, where cases of the new coronavirus are rising, officials say few of those who have tested positive said they attended protests.

According to King County Health Officer Jeff Duchin, just 34 of the more than 1,000 people who tested positive for the new coronavirus in recent weeks in Seattle said they attended a mass demonstration since late May. Overall, almost 3,000 people who were at protests have been tested, and less than 1% have tested positive, Duchin said.

"The data may be imperfect, but we certainly don't have any evidence that those gatherings outdoors are triggering this increase we're seeing," according to Dunchin.

Separately, in a preprint paper published by the National Bureau of Economic Research, researchers tracked more than 300 of the largest cities in the United States to examine any relationship between mass protests and increased cases of the new coronavirus.

The researchers concluded that, based on cellphone data, social distancing actually increased in cities where protests occurred, and they determined that there was "no evidence that net Covid-19 case growth differentially rose following the onset of Black Lives Matter protests."

However, officials in Houston, the epicenter of the new coronavirus surge in Texas, have attributed the increase in cases to a variety of factors, including potentially the protests. Porfirio Villarreal, a spokesperson for the Houston Health Department, said the increase in cases could be attributed to Memorial Day, Mother's Day, or Father's Day gatherings, as well as graduations, bars reopening, and "people interpreting reopening as back to normal."

Why protests may not have led to increased coronavirus cases

Epidemiologists said the conditions at the protests likely weren't conducive for transmitting the new coronavirus.

For instance, in relation to New York specifically, epidemiologists noted the virus was not as prevalent at the time of the protests as it had been at the start of the lockdown, the Times reports. "It seems we in New York City did achieve a substantial decrease in the number of cases, so that made the odds of encountering a case of Covid-19 in these protests quite low," Wafaa El-Sadr, an epidemiology professor at Columbia University, explained. 

Further, according to epidemiologists, the virus doesn't spread as easily outdoors as it does indoors. One study of the virus reviewed 110 cases in Japan and found that transmission odds were 18.7 times greater in closed environments than open-air ones.

The virus is thought to spread primarily through droplets emitted when a person with the virus coughs, sneezes, or talks, the Times reports. When people are outdoors, those droplets are quickly diluted and carried away faster than they would be indoors. 

Protestors were also moving during the demonstrations, which can also assist in dilution, and many protestors were wearing masks, the Times reports.

"This doesn't say that being in a crowd is not risky," Howard Markel, a physician and historian of medicine at the University of Michigan, said. He added that protestors in New York may have been "incredibly lucky" and noted that outdoor crowds can facilitate the transmission of a virus, such as occurred during a war bond parade in Philadelphia during the 1918 Spanish Flu pandemic.

And still other experts say it's too early to tell whether the protests increased virus transmission—especially since many protesters were younger, a demographic in whom more severe cases of the virus and hospitalizations are less common.

"We don't know the impact," Florian Krammer, a virologist at the Ichan School of Medicine at Mount Sinai, said. "We'll see that in the next two weeks" (Goldstein, New York Times, 7/1; Janes, Washington Post, 6/30).