The Impact of Climate Change on Flu

By Matt Longman | 11/13/2017

Flu season has arrived in the U.S., and typically runs from September through March every season. However, many people may not realize that flu season is actually a year-round event that travels the globe. And much like weather events, the spread of the influenza season is also subject to extremes – purportedly the result of climate change.

Impact of Climate Change on Flu Trends

Like the heavy hurricane season recently experienced in the U.S., warmer ocean waters are helping to create stronger flu seasons across the globe. According to research done at Arizona State University, scientists believe that climate change may be a factor in the flu season's increasingly early timing.

Using data going back to 1997, researchers found that warm winters are usually followed by severe and early flu outbreaks. The study found that mild winters preceded an atypically severe flu season 72% of the time, and that those flu seasons started an average of 11 days earlier. During warm winters, flu is less transmittable. That leaves a higher percentage of the population without immunity the next season – leading to a strong flu outbreak and an increase in more severe and fatal cases.

The flu's ability to spread depends heavily on temperature. This is basically the reason flu season occurs in the winter. The structure of the influenza virus allows it to replicate and spread best when air is cold and dry. The virus doesn't survive well in warm, humid air, but thrives in cold temperatures, which is why warm winters usually trigger mild flu seasons.

Impact on Health of Individuals

Healthy adults who get the flu can build up an immunity to similar strains that lasts a couple of years. But those who have no exposure become more vulnerable to the flu the next season, and when temperatures get back to normal, the conditions are ripe for an epidemic to take off early.

Scientists believe we can expect more of the same as climate change progresses. With a global warming of the earth, more mild winters will become more prominent, followed by winters with more typical temperatures—and those associated with more severe flu seasons.

What to Do About the Flu

The take-home? Be vigilant about getting an annual flu vaccine. It still helps to build a person’s immunity, regardless of the severity of the season. Vaccinations remain the best tool for combating the flu, and the potential for unusually early flu seasons serves to highlight the importance of awareness even when the flu season is not at the top of the news cycle.

And if it’s been a mild winter, patients should take advantage of the forewarning that there's a greater likelihood of a severe flu season on the horizon.