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Why do viruses spread more in winter? Cold temps are key



Staying indoors away from wintry weather makes flu and COVID-19 infections more likely. Here’s how to protect yourself.

Thomas Vincz head shot

By Thomas Vincz, Public Relations Manager 

For most, cold weather just isn’t our thing. Unless you’re a virus like the common cold, the flu and, most likely, COVID-19.

The cold winter weather makes it easier for these viruses to spread and infect as many people as possible, potentially making these next few months the most dangerous time of the year.

But what is it about cold weather that makes this season flu season (and possibly COVID-19 season)? Here’s what the latest research shows and how you can stay safer until the spring warms up.

Cold temps create ideal conditions for virus spread

Let’s start off with the flu, since it’s been around and studied for much longer than COVID-19. While flu can strike at any time, flu season usually hits its stride in December and peaks in February – typically, the coldest stretch of the year.

It’s a myth that cold temperatures themselves cause the flu. But the cold weather does change the way the body responds to disease and makes us behave in ways that can increase the risk of infection.

Viruses like influenza tend to enter through the mouth and nose, but our nasal passages usually have strong defenses against them. The cold, however, slows down our ability to clear the mucus in our noses, letting the virus infect the body.

Risks for infection can also increase based on where we spend most of our time during the winter: indoors. Here, we gather closely in rooms that may offer less-than-ideal ventilation and cramped personal space. Heating systems also make indoor air drier. Studies have shown that these conditions can greatly affect the transmission of respiratory viruses.

Scientists are observing similar findings with the coronavirus. As reported by The Wall Street Journal, a dozen recent studies have confirmed that the coronavirus lives longer in cold weather and inside dry, heated homes.

In fact, according to the Centers for Disease Control, the odds of catching COVID-19 indoors are about 18 times higher than outside. This is mainly due to the lack of sunlight and open-air ventilation.

It’s still unknown if COVID-19 will show a seasonal pattern like the flu.

How to reduce your chance of infection

While cold weather contributes to the spread of the flu and COVID-19, it’s still believed that the way we behave drives most transmission between people, including the most recent surge of COVID-19 cases.

That’s actually good news, because it means we have the power to take the necessary steps to curb the spread. For example, researchers from the University of California in Los Angeles recommend creating healthier indoor spaces by humidifying rooms, raising the thermostat and cracking windows to let in more fresh air.

But we can also continue to practice what we’ve been doing this past year:

  • Wear a mask. Masks are a simple way to shield yourself and others from spreading the virus through respiratory droplets.
  • Wash your hands regularly. Frequent handwashing can protect against many infections, including the flu and COVID-19.
  • Avoid touching your eyes, nose and mouth. Keeping your hands away from your face reduces your risk of germs entering your body.
  • Get vaccinated. The annual flu vaccination effectively protects you from the flu or serious complications. The new COVID-19 vaccines are designed to do the same.

As long as it’s cold outside, these are the best ways to avoid catching these viruses. Remember that it’s not too late to get a flu vaccine, and the COVID-19 vaccine will be available to more of us in early 2021.