Did Black Lives Matter protests cause a coronavirus surge?

As the Black Lives Matter protests against systemic racism and police brutality picked up in late May and early June, public health experts acknowledged there was a risk the large demonstrations could lead to a rise in coronavirus cases.

Nearly a month later, Covid-19 diagnoses are climbing, hitting an all-time high on Thursday, with the US arguably in the midst of a second wave of coronavirus cases.

But multiple analyses suggest the protests are not to blame, according to what we know so far. Initial data, reported in the Wall Street Journal and BuzzFeed, found no uptick in Covid-19 cases in cities with major protests. And a recent working paper published by the National Bureau of Economic Research (NBER) found that there was “no significant divergence in the [Covid-19] trends after the protests” in counties with protests and those without.

“There really hasn’t been an overwhelming amount of data to say we saw spikes as a result” of protests, Saskia Popescu, an infectious disease epidemiologist, told me. “That’s a good thing.”

So what is causing the recent uptick in Covid-19 cases, which led to the US hitting its highest number of daily new cases ever this week? Experts pointed to states reopening, particularly allowing indoor gatherings — at bars, restaurants, barbershops, workplaces, and so on — in which the coronavirus is more likely to spread. Studies show that previous measures to close down such gatherings likely helped lower Covid-19 cases.

The protests themselves, however, do not seem to be a major source, at least so far. That suggests that people were able to practice their rights to free speech and assembly without contributing to the ongoing pandemic. It could even mean large gatherings outside, with proper precautions like masks and hand-washing, may be safer than we originally thought, bolstering the case for allowing people to socialize outdoors even as restrictions on large indoor settings continue.

It’s good news. But it’s not what many people, myself included, expected. I asked public health experts and epidemiologists why it might be the case.

They mentioned some important caveats. The coronavirus’s incubation period can take up to two weeks, and people coming back from protests who get sick can take a while to infect their communities, so it’s possible an increase in cases could be linked to the protests down the line. Chance also plays a major role in where outbreaks worsen, and it’s possible protesters simply got lucky in some sense.

“I’ve seen some people say that this means social distancing and these stay-at-home orders were wrong. That’s not the message you should be taking from this at all,” Popescu said. “I really think this is a great example of when you follow public health guidance and you follow harm reduction efforts in activities, you can help break that chain of transmission.”

Here are six reasons the protests may not have led to a big spike in coronavirus cases — and what we can learn from that.

1) The protests were mostly outdoors

Even before this year’s Black Lives Matter demonstrations took off in earnest, experts had already begun advising people that the outdoors seemed, in general, much safer than the cramped indoor spaces that have been the dominant source of big Covid-19 outbreaks.

The coronavirus spreads through airborne droplets and droplets that land on surfaces, which people subsequently pick up with their hands, and the outdoors mitigates these vectors of spread in several ways. First, the open air is going to make it harder for airborne droplets to reach other people. Second, it’s easier to maintain distance from others while outside compared to inside.

Third, there’s some evidence that sunny, warm, and humid weather hurts the coronavirus. Based on the early research so far, heat and UV light appear to kill the virus, while humidity might block airborne droplets from blowing from person to person. The weather isn’t enough to stop the coronavirus — as major Covid-19 outbreaks in sunny and warm Ecuador, Louisiana, Singapore, and, more recently, Arizona demonstrate — but it at least seems to help.

The research into coronavirus and the outdoors, while still very early, backs this up, Kelsey Piper explained for Vox:

One study from China (which has not yet been peer-reviewed) examined 318 outbreaks with three or more people across the country. Only one happened outdoors, and only two people got sick: Every outbreak with three or more cases happened indoors. A different study (also not peer-reviewed) in Japan found that “the odds that a primary case transmitted COVID-19 in a closed environment was 18.7 times greater compared to an open-air environment.”

Indeed, the vast majority of superspreading events were indoors. “We have yet to trace many major outbreaks back to outdoor events,” Abraar Karan, a doctor at Brigham and Women’s Hospital and Harvard, told me. “Most of what we’ve traced back … has been indoors.”

That almost all the Black Lives Matter protests were in marches and rallies outside, then, likely protected demonstrators and their peers from the coronavirus. It’s another piece of evidence supporting doing as much as you can outside over inside during this pandemic.

2) Protesters wore masks, washed their hands, and took other precautions

In talking to protesters, there seemed to be a lot of awareness about the risk of Covid-19 at demonstrations. Participants were asked to wear masks and wash their hands, and in some cases masks and hand sanitizer were given out at the protests. People were advised to take steps to avoid infecting others — to get tested, stay home if they were sick, and quarantine for 14 days after the demonstrations were over.

“People who participated in these protests, it’s not that they didn’t see this pandemic as a public health problem. They understood the risks,” Jaime Slaughter-Acey, an epidemiologist at the University of Minnesota, told me. “At the same time, they also saw the risk of staying silent with respect to police brutality and systemic racism.”

So they tried to strike a balance: protests, but with precautions against Covid-19.

“A lot of individuals [at the protests] were very clear about the potential risk for Covid-19,” Greg Millett, an epidemiologist and vice president and director of public policy at the HIV/AIDS advocacy group amfAR, told me. “Despite the fact there wasn’t social distancing, they were still taking other precautionary measures.”

In some ways, the precautions reflect a broader shift in the US in the past few months. As the pandemic has gone on, Americans as a whole have become more likely to rigorously wash their hands, keep 6 feet from others, wear masks, and avoid going out when they’re sick. For example, polls show the great majority of Americans wear masks sometimes if not always when they go out.

There’s a growing body of evidence suggesting this has a significant effect on reducing Covid-19 transmission. With masks alone, several recent studies have found they reduce transmission. Some experts hypothesize — and early research suggests — masks played a significant role in containing Covid-19 outbreaks in several Asian countries where their use is widespread, like South Korea and Japan.

To put it another way: It seems the things recommended by this public health advice are actually effective — perhaps more effective than many experts and officials initially thought.

So maybe these kinds of protests would have led to some spread of coronavirus a few months ago — if people didn’t wear masks, aggressively wash their hands, and try to stay apart when possible. But now those changes we’ve made may be keeping us safe from the disease, at least in the outdoor settings that the protests mostly took place in.

That, too, has implications beyond the context of protests: It means that when you do go out, you can stay relatively safe if you wear a mask, wash your hands, avoid touching your face, and keep your distance from others.

3) The protesters were relatively young

The Black Lives Matter protests were overwhelmingly led by young people, who are less likely to die or become gravely ill from coronavirus.

It’s not necessarily that young people transmit the coronavirus at lower rates. (The science is still out on that.) It’s also not that young people aren’t susceptible to the virus — there are examples of young people getting seriously sick and dying of Covid-19, with minority communities and people with preexisting conditions hit especially hard by the virus.

But the research shows that young people, especially those without preexisting conditions, are much less likely to suffer the worst complications and die from the coronavirus. That could reduce the chance that Covid-19 cases among younger populations are counted — since young people who contracted the coronavirus but had few to no symptoms are overall less likely to get tested or hospitalized.

“If young people get infected, they’re not going to necessarily get symptomatic disease,” Gregg Gonsalves, an epidemiologist at Yale, told me. “There could have been a lot of asymptomatic or mild infections among the protesters that we’ll never hear about.”

That’s a reason for caution: If protesters were transmitting coronavirus to one another and didn’t know it, they could still end up having the virus and transmitting it to their broader communities — parents, grandparents, teachers, employers, and so on — when they get back to their non-protest lives. Those transmissions could take weeks longer to show up in the data, particularly for protesters who traveled outside their state or county to take part.

At the same time, many local and state governments and public health officials strongly encouraged protesters to get tested — even building pop-up test sites near the protests in some cases — and not many demonstrators were seemingly infected. In Massachusetts, for example, 2.5 percent of protesters’ tests came back positive, which the governor described as “reasonably consistent” with statewide numbers. So perhaps there just wasn’t that much transmission to begin with.

4) The protesters made up a small portion of the overall population

Although hundreds of thousands or millions of people taking part in a protest makes for an impressive demonstration, it’s still a small fraction of the population overall — about 6 percent of adults participated in the protests, based on a survey from the Pew Research Center. Such a relatively small population is simply less likely to cause a major outbreak.

It’s not that an individual or small group can’t cause an outbreak. There have been a few superspreading events that began with one infected individual ending up at the wrong place at the wrong time. As one example, an outbreak in Jordan that ended up infecting more than 70 people appeared to begin with one person — the bride’s father — going to an indoor wedding while he was sick.

All else held equal, though, there’s simply a lower chance of an outbreak if there are fewer segments of the population involved.

This is one reason experts believe that states reopening, not protests, has played the dominant role in the recent spike in Covid-19 cases: While the protests involved a relatively small number of people, states reopening is leading large segments of the population back out — whether due to their workplaces reopening, or simply because they now have places and businesses to go back out to. That’s simply going to overwhelm protests that a fraction of the population was involved in.

“The more people that are going out in the community, and the more contacts they have, the more likely that they hit the right steps for that perfect storm,” Karan said.

5) The protests pushed other people to stay home

One surprising possibility is the Black Lives Matter protests may have led to more social distancing.

This idea comes from a study looking at US cities and counties before and after the protests. The idea goes like this: While it’s almost certain that the protests led demonstrators to reduce their social distancing, the protests may have pushed non-demonstrators back to their homes. Maybe non-protesters feared the demonstrations would become violent (as some did), assumed that businesses would be shut down and traffic would be too congested to go out due to the protests, or worried that the protests could lead to the spread of Covid-19.

Using cellphone tracking data, that’s what the study found: On net, the amount of social distancing — particularly the number of people staying home — actually increased where there were protests.

That seemed to be especially true in areas where the media reported on violence at protests, the study concluded: “We generally find increases in the percent of residents staying at home full-time and time spent at home for both sets of protests [peaceful or violent], though effects are expectedly stronger when protests are accompanied by media reports of violence.”

As a result, the study didn’t detect an increase in Covid-19 cases.

“We went in not knowing if we would find an increase in cases, a decrease in cases, or no effect,” Dhaval Dave, an author of the study, told me. “It was somewhat surprising to us.”

If anything, there may have been a decrease in Covid-19 cases due to the protests, the study found. But Dave cautioned against making too much of that finding, since it wasn’t statistically powerful.

This is where the number of protesters relative to a city’s population makes a difference. If the protests pushed even a small share of the overall non-protesting population back to their homes, that could still have a bigger impact than the protests themselves, on net.

This is just one study; maybe future research with different data or methodology could produce different findings, or more weeks of data will contradict it. The NBER study also couldn’t tease out whether Covid-19 cases increased among the demonstrators themselves.

But the study provided an important takeaway in interpreting the effects of these events. As the paper concluded, “the most visible portion of the population is not always the primary driver of the outcome of interest.”

6) There’s an element of chance

It’s an important caveat to just about any coronavirus story: There’s an element of chance that’s involved in determining whether any event leads to a lot of new coronavirus cases or few to none. So it’s entirely possible that protesters got, in a sense, lucky — and future large outdoor gatherings could still lead to superspreading events.

“Risk is probabilistic,” Gonsalves said. “It’s not absolute.”

During a pandemic, there’s always going to be a risk for a significant outbreak in any event in which people are interacting for hours. That’s going to be true until a vaccine or similar treatment is discovered.

What the protests may show is that the risk can be mitigated — with proper hygiene, mask-wearing, and other recommended steps. “If you invest in public health communication and education messaging, and you have a group of people who are willing to listen and want to be safe while engaging in something, that’s a huge piece of this,” Popescu said.

But, again, experts say even these steps can’t get the risk down to zero. So while someone may determine that a cause is worth the risk of breaking social distancing, it’s important to acknowledge that the risk is always there — and it’s a roll of the die whether the next march, rally, or other large gathering leads to the spread of Covid-19.

“I do think the protests could have had an opportunity to do that,” Millett said, referring to superspreading events. “But thankfully, because of the public health measures that many of the protesters took, we’re just not seeing that spike.”

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