A new study led by researchers at the Brown University School of Public Health finds that weather conditions such as temperature and humidity can help predict when flu outbreaks occur and how severe they will become across North, Central and South America.
The findings, published in PNAS Nexus, suggest how climate change could reshape future flu seasons, with some tropical regions potentially experiencing stronger outbreaks while places with distinct seasons and colder winters could see somewhat smaller outbreaks.
“Investigating how climate affects influenza transmission across different locations is crucial for predicting outbreaks in the present, and in the future as the climate changes,” said first author Aleksandra Stamper, a Ph.D. candidate in Epidemiology at Brown University. “By understanding transmission as a function of humidity and temperature, we can reliably predict how the seasonal influenza outbreak in a state like Wisconsin will differ from the seasonal outbreak in Costa Rica.”
Seasonal influenza infects an estimated 1 billion people worldwide each year and causes hundreds of thousands of deaths. In much of the U.S., Canada and southern South America, where winters are colder, flu activity is typically concentrated and at its peak in the winter months. In tropical regions, influenza often circulates year-round and may produce two periods of heightened activity rather than a single, distinct flu season.
Scientists have long known that climate plays a role in influenza transmission, but it has remained unclear whether the same climate factors could explain outbreak patterns across both tropical and colder regions.