The COVID-19 outbreak continues to expand across the U.S. and globally. What happens when spring and warmer weather arrives?
Some viral respiratory diseases, such as influenza, are seasonal, and cases decrease in the spring and summer. However, we do not know what to expect from the new coronavirus that causes COVID-19.
Lab studies have shown that the quantity of water vapor in the air strongly affects the transmission of influenza, with drier conditions being more favorable. By “drier” we mean lower absolute humidity, which is a measure of the quantity of water molecules in the air. The air is drier in winter both indoors and out. In general, in temperate countries like the U.S., dry cold air is a favorable condition for flu transmission.
Lab studies have investigated only the transmission of the flu so far. We do not know of specific studies for the role of humidity in regard to coronaviruses. Thus, for coronaviruses, the relevance of humidity is unknown.
New viruses may lack a seasonal dependence for infection. As few individuals in the population are immune, a new virus may not require the most favorable conditions to spread. So, we cannot assume that the new coronavirus SARS-CoV-2, the virus that causes COVID-19, will go away on its own when the warmer weather arrives. Also, we lack the data on other weather factors on the coronavirus, such exposure to ultraviolet radiation from the sun.
At this point, we don’t know enough about this virus to understand how the changing weather patterns will impact its behavior. The best approach is to continue healthy practices and follow health officials’ guidance on how to avoid contamination.
Steve Ackerman and Jonathan Martin, professors in the UW-Madison department of Atmospheric and Oceanic Sciences, are guests on WHA radio (970 AM) at 11:45 a.m. the last Monday of each month.
