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Does BA.5 spread more easily outdoors than previous variants? Experts discuss

Outdoor interactions are still safer, but increasingly transmissible strains are definitely a cause for concern.
/ Source: TODAY

Throughout the pandemic, we've learned that COVID-19 is less likely to spread in outdoor interactions than indoor ones. But, because the latest coronavirus variants — like BA.5 — are so much more transmissible, is it time to start wearing a mask more often outside?

The emergence of BA.5 and other highly contagious omicron subvariants is definitely concerning, experts said. And, while outdoor gatherings are still considered safer, there are some cases in which it makes sense to mask up — even when you're outside.

Outdoor interactions are, generally, still much safer than indoor ones

More than two years into the COVID-19 pandemic, we know much more about how the coronavirus spreads than we did back in March of 2020, experts told TODAY.

At this point, it seems like the major way SARS-CoV-2 spreads is when a person infected with COVID-19 expels respiratory droplets containing bits of the virus, said Linsey Marr, Ph.D., an expert in aerosolized virus transmission and a professor of civil and environmental engineering at Virginia Tech.

In certain settings, those droplets can become aerosolized, Dr. Scott Roberts, associate professor and associate medical director for infection prevention at Yale School of Medicine, told TODAY.

When that happens, the aerosolized particles "behave like cigarette smoke," Marr explained. "They're most concentrated close to the person who released them, and they can also stay floating for a long time and spread throughout a room." 

Tiny droplet nuclei, which form when larger droplets fall to the ground and evaporate, may also play a role, Roberts said. These "can travel much farther and linger in the air much longer than the actual droplet," he said.

Indoor environments without much airflow trap these particles inside. "The virus can build up in the air, and it can accumulate over time," Marr explained.

Inside, you can create a safer environment by recirculating air through a room, Neysa Ernst, nurse manager for the Johns Hopkins Biocontainment Unit, told TODAY. "But in the outdoors, that happens naturally," she said.

When you're outdoors, the particles aren't trapped by walls or ceilings, Marr said. "They kind of rapidly disperse and become more diluted in the outdoor air," and are therefore less likely to make others sick. That's why things like outdoor concerts or protests generally haven't been super-spreader events, she said.

But being outdoors isn't a guarantee of safety

The virus “spreads much less easily outside than inside. And by moving events outdoors, you drastically reduce the risk of transmission,” Roberts said. But, even outdoors, the risk is “probably not zero,” he said.

There are certainly settings in which COVID-19 may spread even if you're outside, Roberts said, like a shoulder-to-shoulder packed concert. "If I'm standing one foot next to somebody and they sneeze in my face," he said, "it's pretty hard to avoid a large (amount) of COVID."

So, are you more likely to get COVID-19 outdoors now that even more transmissible variants, like BA.5, are circulating widely?

Unfortunately, there's not much data on whether omicron and its subvariants are more likely to spread outdoors than previous strains, Roberts said. "But, anecdotally, I've heard more reports of people testing positive who say they could have only gotten it outdoors," he said. 

“Overall, the risk outdoors has probably gone up a little because these new variants are more transmissible,” Marr said. “But that’s been true since delta,” she added.

And, so far, BA.5 seems to be more transmissible because it can get around our existing immune protection more easily, not because it causes people to, say, release more viral particles when they cough, Marr said.

So, if exposed to the virus, you may get COVID-19 more easily now than in previous waves — whether you're indoors or outdoors. But being outdoors is still generally a safer bet than being inside where you might be trapped with aerosolized particles.

How to protect yourself:

"If you're going to have any type of gathering, it is much better to do it outside," Ernst said.

But not all outdoor events are the same, Roberts added. A picnic in a park or your backyard with a few friends will likely pose less of a risk than a crowded sporting event full of yelling fans, for instance.

If you're someone who has a higher risk for severe COVID-19 symptoms or you just want to take an extra precautionary step, one of the easiest and most effective things you can do to protect yourself outside is wearing a mask, the experts said.

"Have a good mask," Ernst advised, especially if "you're going to be with people that you're not related to and you cannot be sure of their vaccine status."

While the vaccines aren't as effective at preventing infections with BA.5, they are still doing a good job of protecting against severe consequences of COVID-19. So increased transmissibility “is a cause for concern,” Ernst said, “but it’s a bigger cause to get vaccinated and boosted.”