COVID is now more contagious than ever…

Erin Prater

Sat, July 9, 2022 at 3:02 PM

The outdoors have always been a sanctuary—even more so since the advent of the pandemic.

Spreading COVID outside was possible, but not probable, experts advised in 2020, urging cooped-up citizens to turn to Mother Nature as an antidote to the isolation of lockdowns. Events, dining, and even entire classrooms were moved outside, when feasible.

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-naught value—of around 3.3, meaning that each infected person infected another 3.3 people, on average. That put COVID-19 among the least transmissible human diseases.

Slightly less transmissible were the 1918 pandemic strain of flu, which had an estimated R0 of 2, as does Ebola. On the higher end of the spectrum, mumps has an R0 of 12; measles tops the list at 18.

In order to outcompete, successful COVID variants have become more transmissible with time. Delta had a slightly higher reproductive rate of around 5.1. Then came Omicron, with an reproductive rate almost twice as large: 9.5.

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

New studies suggest that BA.4 and BA.5, currently sweeping the U.S. and countries around the globe, have a growth advantage over BA.2 similar to the growth advantage BA.2 had over BA.1. Thus, the latest dominant COVID subvariants have a reproductive rate of around 18.6, tying or surpassing measles, the world’s most infectious viral disease, according to Esterman.

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

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