Many infectious diseases wax and wane with the changing months. Some, like flu, spike when the weather turns cold, while others, like cholera, thrive during warm, rainy summers. Whether such a pattern applies to SARS-CoV-2 is unclear.
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Some viruses—including influenza and SARS-CoV-2—are packaged in a fragile, fatty outer layer called an envelope that’s both necessary for infection and sensitive to harsh conditions, including heat and the ultraviolet rays found in sunlight. High humidity can weigh down the infectious, airborne droplets needed to ferry the virus from person to person, preventing the microbes from traveling as far.
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As a respiratory virus with a delicate envelope, SARS-CoV-2 has several traits that might someday reveal a seasonal pattern. Years from now, if or when the pathogen returns to the human population, COVID-19 cases may peak when the weather is consistently cold and dry, before dipping down in summer months. For now, though, [epidemiologist Elena] Naumova says that passively waiting for the virus to disappear is “nonsense.” A population’s suceptibility to a given infection trumps all else. And with so many vulnerable individuals around, any warmth-related wanes in disease will do little to rein in its spread.
