WASHINGTON • Mass protests against police brutality that have brought thousands of people out of their homes and onto the streets in cities across America are raising the spectre of new coronavirus outbreaks, prompting political leaders, physicians and public health experts to warn that the crowds could cause a surge in cases.
While many political leaders have affirmed the right of protesters to express themselves, they also urged the demonstrators to wear face masks and maintain social distancing, both to protect themselves and to prevent further community spread of the virus.
More than 100,000 Americans have died of Covid-19. People of colour have been particularly hard hit, with rates of hospitalisations and deaths among black Americans far exceeding those of whites.
The protests in dozens of cities have been spurred most recently by the death last week of Mr George Floyd at the hands of police in Minneapolis. But the unrest and outrage also reflect the dual, cumulative tensions arising from decades of killings by police and the sudden deaths of family and friends from the coronavirus.
The spontaneous protests are occurring as many states have warily begun reopening after weeks of stay-at-home orders, with millions of Americans unemployed. Restaurants, schools, beaches and parks are under scrutiny as the public tentatively practises new forms of social distancing.
In Los Angeles, where demonstrations led to the closing of virus testing sites last Saturday, Mayor Eric Garcetti warned that the protests could become "super-spreader events", referring to the types of gatherings that can lead to an explosion of secondary infections.
Maryland's Governor Larry Hogan expressed concern that his state would see a spike in cases in about two weeks, which is about how long it takes for symptoms to emerge after someone is infected, while Atlanta's Mayor Keisha Lance Bottoms advised people who were out protesting "to go get a Covid-19 test this week".
Some infectious disease experts were reassured by the fact that the protests were held outdoors, saying the open-air settings could mitigate the risk of transmission. In addition, many of the demonstrators were wearing masks, and in some places, they appeared to be avoiding clustering too closely.
"The outdoor air dilutes the virus and reduces the infectious dose that might be out there, and if there are breezes blowing, that further dilutes the virus in the air," said Dr William Schaffner, an infectious disease expert at Vanderbilt University. "There was literally a lot of running around, which means they're exhaling more profoundly, but also passing each other very quickly."
But others were more concerned about the risk posed by the marches. Dr Howard Markel, a medical historian who studies pandemics, likened the protest crowds to the bond parades held in cities like Philadelphia and Detroit in the midst of the 1918 influenza pandemic, which were often followed by spikes in influenza cases.
"Yes, the protests are outside, but they are all really close to each other, and in those cases, being outside doesn't protect you nearly as much," Dr Markel said. "Public gatherings are public gatherings - it doesn't matter what you're protesting or cheering."
Though many protesters were wearing masks, others were not. The coronavirus is mainly transmitted through respiratory droplets spread when people talk, cough or sneeze; screaming and shouting slogans during a protest can accelerate the spread, Dr Markel said.
Also, tear gas and pepper spray, which police have used to disperse crowds, cause people to tear up and cough, and increase respiratory secretions from the eyes, nose and mouth, further enhancing the possibility of transmission.