Your outdoor COVID protection isn’t what it was in 2020. Therefore, it is time to think more critically about outdoor gatherings

Nature has always been a sanctuary – especially since the onset of the pandemic.

Spreading COVID outdoors is possible but not likely, experts advised in 2020, urging confined citizens to turn to Mother Nature as an antidote to lockdown isolation. Events, meals and even entire classrooms have been moved outside where possible.

But Omicron was a game changer in more ways than one.

The original Wuhan strain of COVID-19 had a reproductive rate — also known as an R0 or R-zero — of about 3.3, meaning that each infected person infected another 3.3 people on average. This makes COVID-19 one of the least communicable human diseases.

Slightly less transmissible was the 1918 pandemic flu strain, which had an estimated R0 of 2, as did Ebola. At the high end of the spectrum, mumps has an R0 of 12; Measles tops the list at 18.

To stay competitive, successful COVID variants have become more transmissible over time. Delta had a slightly higher reproductive rate of about 5.1. Then came Omicron with a reproduction rate almost twice as high: 9.5.

The so-called “stealth omicron,” nicknamed for its ability to evade detection by PCR tests, was about 1.4 times more transmissible than BA.1, bringing its reproductive rate to about 13.3, Adrian Esterman, a professor of biostatistics and epidemiology at the University of South Australia, recently wrote on the academic news site The conversation.

New studies suggest that BA.4 and BA.5, currently sweeping the US and countries around the world, have a growth advantage over BA.2 equal to the growth advantage BA.2 had over BA.1. For example, the latest dominant COVID subvariants have a reproductive rate of about 18.6, according to Esterman, surpassing measles, the world’s most contagious viral disease.

Greater transmissibility means greater transmissibility in any environment, indoors or out — even if it’s still safer outside, Maimuna Majumder, an assistant professor at Harvard Medical School and a computational epidemiologist at Boston Children’s Hospital, recently told NPR.

Complementing the use is the fact that newer subvariants such as BA.4 and BA.5 are the most immune-avoidable to date, with the ability to evade antibodies from both vaccines and previous infections.

All to say that your outdoor shelter isn’t what it was in 2020 – and it might be time to think more critically about outdoor gatherings.

For those hosting events, Majumder recommended reducing attendance at gatherings, a move that can “drastically” reduce transmission. She also suggested making sure guests are vaccinated, have recently tested negative and are symptom free.

If an outdoor event is crowded, especially if there’s singing or shouting — maybe a concert or protest — masking is a good idea, she advised.

While outdoor events are safer than indoor events, they “are not 100% safe,” Majumder told the news outlet. “The more crowded an outdoor space is, the more it mimics an indoor space when we’re exposed to the shared air.”

She warns that outer tents, which don’t have flaps that let air in, “are not that different from inner tents” in terms of COVID transmission risk.

As for indoor activities outside the home — mask up even if your trips are short, she recommended: It’s more possible than ever to catch COVID in passing.

This story was originally published on Fortune.com