Warm weather and COVID-19: hope on the horizon?

By: Dr. Josh Eachus

A common idea circulating—will warm weather curtail the novel coronavirus? Assumptions are being made. Social media aggravates misinformation at times when facts are most important. The greatest enemy to scientists in crises is the spread of rumors and innuendo during situations that require clear, actionable information. Meteorologists frequently remind, no two storms are the same, comparisons are irresponsible and doing so sets the stage for harmful consequences. The medical field faces a similar messaging challenge.

Dr.Marc Lipsitch of Harvard’s Center for Communicable Diseases notes some important disclaimers. First, remember that S.A.R.S. did not go away as temperatures warmed. Like what has been done with COVID-19, expansive social distancing measures were imparted in many countries to slow transmission. Using Canada as an example, once the measures were eased, cases saw a secondary spike in the warm season. Second, predicting how a new virus will behave based on other coronaviruses is speculative at best. Dr. Nancy Messonier of the Center for Disease Control’s National Center for Immunization and Respiratory Disease echoes that. “I think I would caution over interpreting that hypothesis,” she told reporters on a conference call, “I’m happy to hope that it goes down as the weather warms up, but I think it’s premature to assume that.” Dr. Christopher Thomas of Our Lady of Lake reinforced that answer on WBRZ in Baton Rouge during an interview with News 2’s Chris Nakamoto. For instance, just because you like regular cheese pizza, does not mean you will like regular cheese pizza from every restaurant—all have their own “flavor” and so do viruses.

As long as the limitations of comparisons are understood, it may be helpful (perhaps just hopeful) to evaluate what is known about similar diseases.  According to Messonier,Most viral respiratory diseases are seasonal, and we’ll use, as an example, influenza.  Influenza has a season.  It can alter a little bit but it’s generally… as we head towards spring and summer, we expect the cases of influenza in the United States to fall off.”

In the winter, the outdoor air is colder, and the air is dryer usually both indoors and out. Lab tests have proven that very humid air significantly slows flu transmission. However, flus are not identical to coronaviruses and Lipsitch, at least, is unaware of coronavirus lab tests the replicate results of the flu lab tests.

The seasonal patterns in flus cannot be attributed solely to weather; there are non-environmental factors that also play a role. In the winter, people spend more time in poorly ventilated indoor spaces therefore in close quarters with others, which makes transmission more likely. Lipsitch says there are even hypothesis that Vitamin D, resulting from sun exposure, aids the immune system—and typically, people spend more time in the sun during the warmer seasons.

Despite all of the laboratory science and hypothetical evidence for seasonality in flus, “We haven’t even been through six weeks of it, much less a year,” said Messonier. Lipsitch cautions, “Even seasonal infections can happen “out of season” when they are new. New viruses have a temporary but important advantage – few or no individuals in the population are immune to them.”




Josh Eachus is the chief meteorologist at WBRZ News 2 in Baton Rouge. Josh received his Ph.D. from Louisiana State University in December 2017 having published research and expertise on effective communication of weather, especially during high impact events such as hurricanes, floods and tornadoes.

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