(AP) — As demonstrators flooded streets across America to decry the killing of George Floyd, public health experts watched in alarm — the close proximity of protesters and their failures in many cases to wear masks, along with the police using tear gas, could fuel new transmissions of the coronavirus.

The protests have come just as communities across the nation loosen restrictions on businesses and public life that have helped slow the spread of the virus, deepening concern that the two factors taken together could create a national resurgence in cases.

The AP’s review focused on large metro counties — the central counties within metro areas with more than 1 million people — that showed the highest rates of new cases per capita over the past 14 days.

While case numbers and deaths have been trending down in several of the cities where the largest protests have occurred, the number of people in those places infected with the virus — and with the ability to spread it — remains high.

Osterholm and other public health experts note, however, that the protests aren’t necessarily as alarming as other events that could fuel new cases because they take place outside and many people are wearing masks.

David Eisenman, director of the Center for Public Health and Disasters at the UCLA Fielding School of Public Health, said he feared partisan forces might accuse cities of bringing fresh cases on themselves.

Leana Wen, an emergency physician and public health professor at George Washington University, said the hospitalizations for coronavirus in the Washington metro area have been on the decline but that she knows that could change.

Public health experts said it will take two to three weeks to know whether the protests cause a surge in coronavirus cases.

It also comes on the heels of the Memorial Day weekend, when many people attended large gatherings, so experts already were bracing for a case increase, said Jennifer Nuzzo, an epidemiologist at Johns Hopkins University.

In Los Angeles, barbershops and in-person dining were allowed to resume last weekend, just as protests descended into destruction and more than 1,000 people were arrested.

Hundreds of people also were arrested in Chicago, where Cook County has had among the highest per capita rates of new cases of any large county in the nation, with 283 new cases per 100,000 population in the past two weeks.