Despite all the research on the seasonality of the flu, the seemingly simple answer as to why flu outbreaks in the United States happen in the wintertime continues to remain elusive. Making matters more pressing is that nailing down the link between the two could prove very useful to public health officials preparing for flu outbreaks. So what
do we know about the relationship between cold weather and the flu?
It's a puzzle that`s baffled scientists for decades. Quite a few myths have been perpetuated over the years, and sometimes it`s hard to tell what spreads faster during flu season- the viruses, or the lore surrounding them. Over the years, scientists have come up with many theories as to why influenza outbreaks are so strongly tied to the calendar. Here's a few:
- Perhaps it's because people are inside more in cold weather so the virus spreads more easily?
- Maybe it's because people aren't out in the sun making Vitamin D, and their immune systems are weak?
- Could it be that people travel for the holidays at certain times of the year, helping spread the virus?
- Might it be that a cold temperature hurts the human immune system, causing an increase in flu rates?
So far, not one of these theories has produced any solid evidence of a link. But there are a couple of promising studies:
Research has shown that the flu survives and spreads better when the air is dry. This suggests that the flu might survive better when the humidity is low.
Typically, humidity is lowest during the wintertime when the air tends to be very cold and dry. These seasonal changes in humidity might explain why more people get sick from the flu during the winter.
Another theory recently published in a scientific paper contends that changes in outdoor temperatures, perhaps coupled with changes in cloud cover, humidity, and wind, may force changes in the use of indoor ventilation and thermal units that alter the likelihood of infection. But the researchers in this study were reluctant to make any direct correlations.
So after all the research and knowledge, as well as the myriad of debunked or unproven myths, we still don`t know definitively what the connections are between weather changes and the flu. In the meantime, get a flu shot and hope winter isn`t a brutal one this year - if not for the flu threat, then for the heating bills!
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Story image: This 2009 image provided by the Centers for Disease Control and Prevention shows an H1N1 swine flu virus. Centers for Disease Control and Prevention via Wikipedia