According to Princeton researchers, higher temperatures and increased rainfall could make outbreaks of influenza and respiratory syncytial virus less severe but more common.

The researchers reported in the journal Nature Communications that RSV epidemics are subject to different climatic factors depending on location. Fluctuations in humidity are the driving force behind the virus’ spread in temperate northern locations, while RSV epidemics track the rainy season in tropical locales. The virus is governed by both humidity and rainfall in “crossover” locations such as Mexico’s Sinaloa state that typically experience two epidemic peaks each year.

When the researchers coupled their results with climate change models, they found that while outbreaks of RSV became generally less severe, the virus’ peak-infection cycle shifted northward, explained first author Rachel Baker, a postdoctoral research associate in the Princeton Environmental Institute (PEI). In many areas, particularly in the northern United States, epidemics of RSV could become more common and strike earlier in the year.