For three months, the main message coming from politicians, the media and medical experts was to stay a minimum of six feet away from others to reduce the likelihood of transmitting COVID-19. And so it can be alarming to see protestors standing shoulder to shoulder at rallies against police brutality in response to the May 25 killing of George Floyd. Yet according to a number of public health experts, these protests are not the greatest health risk faced by the Black people at them—racism is.

“White supremacy is a lethal public health issue that predates and contributes to COVID-19,” reads an open letter which NPR reports was originally written by infectious disease experts at the University of Washington. Signed by dozens of public health and disease experts, NPR states, “the letter cited a number of systemic problems, from the disproportionately high rate at which black people have been killed by police in the U.S. to disparities in life expectancy and other vital categories — including black Americans’ higher death rate from the coronavirus.”

“Data is showing that blacks and Latinos have been disproportionately affected by COVID-19 in many states,” Dr. Elaine Nsoesie, an assistant professor of global health at Boston University and one of the signers of the letter, told NPR in an interview. “Racism is one of the reasons this disparity exists. Racism is a social determinant of health. It affects the physical and mental health of blacks in the U.S. So I wouldn’t weigh these crises separately.”

These same public health experts stressed a number of measures that could reduce the chances of transmission at rallies. According to NPR, they include: wearing masks; law enforcement agencies not using tear gas, smoke and other irritants (as these encourage touching the face and eyes and can also make people more susceptible to infection and worsen existing health conditions); not singing and shouting to reduce the threat of person-to-person transmission.

At the same time, they acknowledge that the nation should be prepared for a rise in the number of COVID-19 cases in the near future, and that public health agencies should ready themselves to handle the influx. “Risk of transmission is lower in open spaces, but wherever there is a gathering there is still the risk of transmitting the virus,” said Nsoesie.

The protests, which have taken place in cities around the world, were prompted by the death of Floyd by Minneapolis police officer Derek Chauvin. Floyd, who was handcuffed, died shortly after the white officer pinned him to the ground and pressed his knee into his back as Floyd said “I can’t breathe…please stop.” Video of the incident sparked global outrage.