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BA.5 Outdoor transmission: the risk of getting COVID-19

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WWhen the pandemic first started, COVID-19 seemed to be lurking around every corner, so it came as a great relief when scientists determined that the virus doesn’t spread easily outdoors. This summer, however, that sense of relative security came up for discussion. With the BA.5 sub-variant driving a new wave in the US, can people count on the open air to keep them safe?

The truth is, being outdoors has never been a surefire way to prevent transmission of COVID-19, especially at crowded events, such as music festivals, which have historically been linked to outbreaks. “In our study, we definitely hear from people who were quite obviously infected outside, so it’s happening,” said Dr. Donald Milton, a professor of environmental health at the University of Maryland School of Public Health, who is the principal investigator of an ongoing study on the transmission of HIV. COVID-19. Sure, “it’s still a lower risk than indoors,” but Milton isn’t comfortable in any outdoor situation. “I didn’t go to the fireworks on July 4 and I didn’t get into the crowds,” he says. “My outdoor activities mainly consist of sports, cycling, walking and jogging.”

BA.5 seems to evade immunity from vaccines and previous infections more easily than previous subvariants, which experts say increase the risk no matter where you are. “We’re more susceptible to hosts, and we’re more susceptible whether we’re indoors or out,” said Dr. Duane Wesemann, an associate professor at Harvard Medical School and an immunologist at Brigham and Women’s Hospital.

While scientists are still learning about BA.5, it is becoming increasingly clear that it has advantages over previous variants that help it evade the immune system’s defenses. Like other Omicron subvariants, BA.5 has evolved new mutations — in this case in the spike protein, the part of the virus that binds to cells — that may help it evade immunity, explains Bing Chen, a researcher associate professor of medicine at Harvard Medical School and Boston Children’s Hospital who studies molecular medicine. “Our antibodies are slightly less effective against BA.5 compared to BA.1 and Delta,” he says.

The increased transmission of BA.5 and our decreased immune defenses mean that outdoor transmission of COVID-19 has become more likely. But that doesn’t mean being outside isn’t protection, especially if you take other precautions as well. As always, context matters. Being out in the open and away from other people is safer than being in a crowd with poorer air circulation, such as a packed baseball stadium without a breeze, Milton says. “Outdoors remains a much lower risk environment than indoors,” said Linsey Marr, a professor of civil and environmental engineering at Virginia Tech. “Out-of-home transfer is most likely to take place in a face-to-face meeting. There is also the possibility of transmission if you happen to be close enough and upwind of someone who is infected.”

The same precautions that protect you indoors can also help outdoors, such as avoiding crowds and wearing a mask when you’re with other people. Knowing about COVID-19 vaccinations can also make you safer, as the shots prompt the immune system to develop multiple types of defenses against COVID-19, Wesemann says. While the virus is getting better at bypassing the neutralizing antibodies — which help keep people from getting infected in the first place — vaccines also trigger longer-lasting types of immune responses. Ultimately, this means that vaccinated people who become infected with COVID-19 are less likely to become very sick or die from the disease, regardless of where they were infected.

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