Are Flu Outbreaks Connected to Weather Patterns?  

Jake Newby

| 4 min read

Are Flu Outbreaks Connected to Weather Patterns?  
Flu season aligns with the winter months. We all know this. But do we know why, exactly?
Influenza (the flu) is at its peak during America’s coldest months of the year, between December and February. But activity can last as late as May, according to the Centers for Disease Control and Prevention (CDC).
We do know that in winter climates, people spend more time indoors with limited ventilation which increases the likelihood of viral spread from person to person.
There are many schools of thought as to how weather patterns shape the severity and longevity of flu season. Most scientists and researchers agree that two weather factors predominantly affect it: Temperature and humidity.
It’s a misnomer that cold temperatures cause the flu, as a person needs to be infected by the influenza virus to have it. But many studies show that cold weather exacerbates the severity of the flu and enables it to spread faster. 
The rubbery, outer membrane of the influenza virus is made of lipids. Researchers with the National Institutes of Health found that these lipids – composed mostly of oils, waxes and cholesterol – solidify into gel form in extremely cold temperatures.
It’s as if the flu virus puts on the same big, puffy winter jacket that we do in the winter.
However, when temperatures rise, this gel melts, as lipids do not mix well with water. This could explain why the highly contagious virus can withstand cooler temperatures and fluently spread from person to person in the winter, and why it losses it’s ability to spread from person to person when the weather warms in the spring.
What about humidity’s role in flu season?
Multiple studies have found the flu to be more prevalent when the air is dry. In 2019, Yale researchers found a connection between low humidity and our body’s inability to clear allergens from our airways, while also limiting the ability of the body’s airway cells to repair lung tissue damaged by influenza.
Conversely, researchers in 2013 found that transmission of the flu through a person’s cough decreases when relative humidity is at or above 40%. This is another indicator that the flu has a hard time coexisting with warm, humid weather.
Another factor to consider when it comes to weather’s relationship with the flu is sunlight and vitamin D, and the role they play in protecting us from flu-like symptoms. Studies show that vitamin D protects against upper respiratory infections.
Keep your vitamin D intake up in the winter by bundling up and walking outdoors on a semi-regular basis. You can also discuss vitamin D supplementation with your primary care provider and whether it’s right for you. Multiple studies have found that vitamin D supplementation, when taken in appropriate doses, can protect against respiratory illness.
Reduce the risk of catching or spreading influenza by developing healthy habits to prevent the flu. Here are some suggestions from the CDC:
  • Avoid close contact with people who are sick.
  • Stay home when you are sick.
  • Cover your mouth and nose.
  • Wash your hands.
  • Avoid touching your eyes, nose, or mouth.
If you’re a Blue Cross Blue Shield of Michigan or Blue Care Network member, visit a participating pharmacy with your member ID card to get your flu shot today. While most pharmacies will accept your coverage, be sure to ask before you get your vaccine. Then, write down the date and let your doctor know at your next appointment so he or she can keep your immunization chart up to date.
You can also schedule an appointment with your primary doctor to get one. Your office visit copayment may apply.
For Blue Cross members without Blue Cross pharmacy coverage: Visit to see a list of immunizing pharmacies that provide vaccines under your medical coverage.
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Photo credit: Getty Images

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