For more than two months, the authorities had been urging New Yorkers to stay indoors and keep their distance from others. But after the police killed George Floyd in Minneapolis, tens of thousands of New Yorkers poured into the streets, day and night, to protest police brutality and racism.
Epidemiologists braced for a surge of new coronavirus cases. But it has not come yet.
On May 27, the day before the protests began in New York City, some 754 Covid-19 cases were diagnosed, according to the city’s Department of Health. That was the last time the city recorded more than 700 cases on a single day.
By the end of the first week of protests, the city was recording slightly more than 500 cases a day. By the end of the second week of protests, the case counts were in the low 400s or high 300s a day. They’ve continued to drop slightly. The last time New York City recorded more than 300 cases was on June 22.
“We’ve been looking very closely at the number of positive cases every day to see if there is an uptick in the context of the protests,” Ted Long, executive director of the city’s contact tracing program, said. “We have not seen that.”
In interviews, several epidemiologists expressed either surprise or relief, and offered theories for what occurred. This is what we know:
The virus spread in New York City was already slowing down.
The lockdown enacted in March worked. By the end of May, when the protests began, the virus was not as prevalent in New York as it had been when the lockdown began.
“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,” said Wafaa El-Sadr, an epidemiology professor at Columbia University.
Exactly how low is tough to gauge. Throughout June, somewhere between 10,000 and 35,000 New Yorkers per day were tested for Covid-19. The percentage of coronavirus tests in New York City consistently turning up positive declined in June, from about 3 percent at the start to 2 percent. But New York City has released little specific information about current hot spots or clusters, or current infection rates among different age groups.
Some cities and states have made a point of testing demonstrators and released their findings.
In New York, Governor Cuomo pledged in early June to dedicate 15 testing sites in the city exclusively to people who attended protests. But a state Health Department spokesman said that data is not yet available.
Kitaw Demissie, an epidemiologist and dean of SUNY Downstate School of Public Health in Brooklyn, said it was possible that in areas with accelerating outbreaks — such as some southern and western states — the mass demonstrations could well play a role in the spread of the virus.
Outdoor transmission is more rare.
Conditions at the demonstrations may not have been conducive for transmission, mainly because the protests occurred outdoors, epidemiologists said.
The virus spreads far more easily indoors than outdoors, and close contact indoors is believed to be the main driver of transmission, epidemiologists say. One study based on a review of 110 cases in Japan found that the odds of transmission were 18.7 times higher in closed environments — everything from fitness studios to tents — than in open-air environments. Another study involving a review of thousands of cases in China found only a single instance of outdoor transmission.
In Minnesota, where Mr. Floyd was killed, cases among young adults climbed substantially over June. But officials said that gatherings in re-opened bars were partly to blame.
The virus is thought to be spread primarily through the virus-laden droplets emitted when a contagious person coughs, sneezes or talks. When outdoors, this virus-laden air is more quickly diluted and carried away than it would be in a poorly ventilated room. Because a certain quantity of virus is needed for an infectious dose, the dilution can make a significant difference, epidemiologists say.
Another potential factor: Demonstrators were often on the move, marching at a brisk pace. That may have promoted dilution and also spaced people out from each other.
“This doesn’t say that being in a crowd is not risky,” said Howard Markel, a physician and historian of medicine at the University of Michigan who has written on past epidemics. He said that protesters in New York may have just been “incredibly lucky.”
He noted that outdoor crowds can accelerate the spread of respiratory viruses — most notoriously during a war bond parade in Philadelphia during the 1918 influenza pandemic.
Most protesters wore masks.
New York City’s Health Department had gone so far as to urge protesters not to chant or yell — which can increase the likelihood of transmission — but to instead carry signs and consider bringing a drum.
But while that bit of advice went largely unheeded, most protesters adhered to another: Wear a mask.
Carlos Polanco, 21, from Brooklyn, who protested for 22 or 23 days straight, often out front at protests with a bullhorn, said that organizers made a point of bringing extra masks and distributing them to demonstrators. Mr. Polanco, a rising senior at Dartmouth College, said that he tried to wear a mask except when he was delivering a speech or leading chants — during which time he tried to keep his six feet of distance from others, he said.
And many protesters complained when police officers at protests did not wear masks.
We could still see a wave of infections tied to the protests.
Some scientists say it’s still too early to tell how much transmission occurred at the demonstrations in New York. One reason is that many protesters were young adults — a demographic in whom severe cases and hospitalizations are less common. As a result, a rise in cases that started within this demographic might remain undetected by public health officials for longer.
“We don’t know the impact. We’ll see that in the next two weeks,” Florian Krammer, a virologist at the Icahn School of Medicine at Mount Sinai, said in an interview last week.
Moreover, city officials have instructed contact tracers not to ask new Covid-19 patients if they attended protests, according to a report in The City, a nonprofit news organization.
And the protests continue. Hundreds gathered at City Hall Park over the past week, to demand deep cuts to the New York Police Department budget. Some protesters are camping out in sleeping bags or under tarps. The gathering is drawing some comparisons to the Occupy Wall Street encampment at nearby Zuccotti Park in 2011. Rarely remembered, a vicious cough, called “Zuccotti lung,” circulated around that encampment.
So far there has been no clear increase in patients in emergency rooms complaining of pneumonia or flu-like symptoms — a metric the city’s Health Department tracks as an early warning system for Covid-19 transmission.
But public health experts cautioned against drawing too much reassurance from New York’s experience. “Like most every other aspect of this pandemic the most predictable thing is the unpredictability,” said Professor Markel, the historian and physician from the University of Michigan.