A month after mass demonstrations against racial injustice filled city streets across America, epidemiologists and a McClatchy analysis of COVID-19 case data suggest the protests did not lead to dramatic increases in transmission, providing further insight into what does − and doesn't − lead the coronavirus to spread.
To the surprise of some epidemiologists, the surge of protests following George Floyd's death in Minneapolis police custody on May 25 hasn't consistently led to a surge in COVID-19 cases in the cities where those protests occurred. Some metropolitan areas such as Miami, Dallas and Boise, Idaho, have seen increased case counts and "positivity rates" − the percentage of coronavirus tests that come back positive − since May 25. But other cities that had some of the largest protests, such as Minneapolis, Chicago, Washington and New York, have actually seen a decline in case counts and prevalence of the virus, as measured by the percentage of positive tests.
If the protests had played a direct and meaningful role in the coronavirus spikes, epidemiologists say they would have expected to see a consistent trend throughout cities across the country that saw mass demonstrations. But that has not occurred. In Miami, for example, the positivity rate was roughly 4% on May 25. Since June 15, it's been in double digits practically every day, and has even topped 20% on a handful of days. By contrast, in Washington, D.C., the positivity rate was above 10% in late May, but has consistently been below 5% since mid-June.
The recent data has led epidemiologists to question whether large outdoor gatherings have served as the "superspreader" events they initially feared −and is providing them with further evidence that major coronavirus spreading events are occurring primarily at indoor facilities.
The protests led to more social distancing
There was a concern that large group mass gatherings would be risky," said Dr. David Alden Drew, an epidemiologist at Massachusetts General Hospital and the Harvard T.H. Chan School of Public Health, referring to the Floyd demonstrations. "But I haven't seen any compelling data that shows there are spikes in incidence related to this." "It is consistent with what we've been seeing, that indoor events are much more dangerous than outdoor events, for sure," Drew said. Drew has helped launch the COronavirus Pandemic Epidemiology (COPE) Consortium, an app being used in the United States to study the symptoms of millions of individuals with COVID-19 and track the spread of the virus. While the app has not examined the impact of specific events, such as protests or campaign rallies, mobile phone data was used in one preliminary study released in June that found the protests actually led to increased social distancing on a citywide basis −not a statistical increase in cases.
"When we have 'superspreader' events, those do tend to get picked up with the limited contact tracing we have throughout the country, and they tend to get publicized _ I think that if any public health department was seeing that link, we'd be hearing it, and we aren't," said Dr. Laura Jarmila Rasmussen-Torvik, chief of epidemiology in the Department of Preventive Medicine at Northwestern University's Feinberg School of Medicine.
"All of the prominent case theories have seen superspreading events in inside areas," Rasmussen-Torvik said. "We have heard very, very little about spread outside."
Scientists examining the linkage between protests and spiking cases have struggled with a multitude of factors. Many cities began reopening around the same time that the protests began, which also coincided with Memorial Day, a major federal holiday for family and community gatherings that marks the start of warmer weather. Some states are not tracking positivity rates at the city or county level, making it impossible to determine whether an increase in cases has been driven by the introduction of the virus in rural areas versus in cities that experienced protests.
Research from other countries show superspreading indoors
But overseas, in countries with robust contact tracing programs, scientists have most commonly linked superspreading events to indoor facilities. Epidemiologists are increasingly confident that risk is especially pronounced in restaurants and bars − public venues where individuals must remove their masks to eat and drink. In the United States, experts note that cities which saw the largest protests and are showing a decline in coronavirus cases −such as Washington and New York _ prohibited indoor dining throughout most of June, while those that opened up indoor facilities in May are the ones seeing increases.
"Most of the cases where you've seen superspreading events have been indoors −choirs and churches, bars and restaurants. And those are generally indoor places," Lloyd Hough, a senior official and biology expert with the Department of Homeland Security's Science and Technology Directorate, told McClatchy this week. McClatchy analyzed four weeks of data in a handful of cities where demonstrations took place, examining case numbers and positivity rates, when available, since the week before the Floyd protests began. The positivity rate is one statistic that epidemiologists have identified as a reliable marker to determine whether prevalence of COVID-19 is actually increasing, or whether higher case numbers are due to increased testing. When available, McClatchy examined case counts leading up to Floyd's death on May 25, and in the weeks following, since epidemiologists say there is normally a lag time of one to two weeks between when people are infected with COVID-19 and when they are tested. McClatchy looked at daily case count and testing data at the city or county level − for Boise it was the public health district which includes the city −through the end of June.
Larger cities saw drastic decreases after protests
The analysis showed that some cities, such as New York and Washington, which had some of the largest protests in the country saw a decline in both raw cases and the percentage of positive tests in the weeks following the protests, while other cities, such as Miami and Dallas, saw increases in both after the protests. Some jurisdictions don't release testing data at a city or county level, making it impossible to determine the rate of COVID-19 tests that are positive. Still, it's possible to draw some conclusions by looking at raw case counts and statewide positivity rates.
In the two weeks prior to May 30, when protests in Raleigh began, COVID-19 cases increased 47% and the average daily increase was 39 in Wake County, the second most populous county in North Carolina. In the two weeks following May 30, positive cases increased 79% and the daily average of new cases more than doubled to 95.
While the number of completed tests in Wake County has not been released, the positive rate for the state during that time increased steadily from 6% to 10%, which suggests that the positivity rate might have increased in Wake County during that time period. The state began to reopen in late May, right before the protests, making it difficult to determine whether the increases were due to eased restrictions or the protests.
By contrast, Minneapolis, where Floyd died, saw a decreased number of cases in the weeks following his death. While the positive test rate isn't available for Minneapolis or for the county it's in, Hennepin County, the positive test rate dropped dramatically statewide.
In Florida, which has seen a large spike in positivity both in Miami-Dade County and across the state, the spike started in mid-June, as the county's positivity rate started creeping into double digits, where it has mostly remained ever since, topping 20% on a handful of days.
Miami-Dade County Mayor Carlos Gimenez blasted graduation parties and restaurants not following social distancing rules, but also attributed some of the spike to protests, without offering further evidence of how the protests and COVID-19 increase were linked. The county also began to reopen in late May, right before the protests began.
Further complicating the matter is that younger Americans − who were more likely to engage in protests, are less likely to exhibit symptoms and are less likely to get tested − have been driving recent coronavirus spikes in several communities across the South. The full extent of infections at the protests may never be known, because some individuals in younger age groups who attended may not have been tested or have had symptoms. But if young people contracted the virus while protesting, and if those infections were missed because they are typically asymptomatic, they still would be spreading the virus and the secondary effects of that spread would be apparent by now in cities that experienced protests, experts say.
"If it were so striking, we would see it consistently across the country," said Eric Topol, founder and director of the Scripps Research Translational Institute.
"There had to be some increase from the protests, but the fact that it was not consistently seen and not large mitigates concern."
Determining the protests and COVID-19 link may take weeks
In mid-June, Dr. Anthony Fauci, the top infectious disease expert on the White House Coronavirus Task Force, told McClatchy that the Trump administration was closely monitoring the effects of mass outdoor and indoor gatherings on the evolving pandemic.
Like other experts in the field, Fauci cautioned that it would be difficult to draw definitive conclusions on the linkage, because protests over the death of Floyd and city and statewide reopenings were happening at the same time. "If in fact there is an increase in infections, at the opening or at an event like a demonstration or a big party or what have you, people will get infected.
“Most of the people there are young people. Most of them are going to have an asymptomatic infection. Most of them are not going to go get tested," Fauci said. "So what will happen is that it will take a couple of weeks for the people to essentially get infected enough to then infect someone else who's vulnerable, who will then infect someone who actually winds up in the hospital."
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