Cold weather may not be the only reason you get chills. Low temperatures can increase the likelihood of getting sick. The body is not as effective at fighting a virus when cold air enters the nose and upper airways, so viruses such as the common cold, the flu and COVID-19 often spread more easily in the winter.

"As the temperature starts to drop, we have more viruses in the environment, so we have to be more careful in the winter to prevent catching illnesses," says Northwestern Medicine Primary Care Physician Winston D. Rajendram, MD. 

Go Outside Anyway

If being cold can make you sick, it might seem like staying inside is your safest choice. For most people, it's not. Not only are you more likely to pick up germs indoors, you're also limiting your sun exposure, which can cause your vitamin D levels to plunge. Low levels of vitamin D have been linked to influenza A and a weakened immune system, plus a variety of health issues, including fatigue, general achiness and even cancer.

However, "People who are elderly, have chronic illnesses or are immunocompromised should avoid cold weather and being outside because they can catch a virus more easily," notes Dr. Rajendram.

Dangers of Dry Air

Dry winter air is great for viruses — and not so great for you. Research shows that dry winter air allows the flu virus to spread. Air inside your home also tends to be dry in the winter due to heating, and this can dry out your nasal passages, making them less effective at fighting off viruses. Plus, viruses spread more easily through dry air because fewer water molecules are available to interfere with their projection through the air when expelled through a sneeze or cough. One study found that good ventilation combined with high relative humidity indoors rendered the influenza A virus inactive.

If You Can't Fly South

Dr. Rajendram suggests the following strategies to avoid catching and spreading a viral infection:

• Wear a mask. Masks can help prevent respiratory droplets from reaching other people, which is one of the ways germs spread. You should wear a mask, even if you do not feel sick.
• Wash your hands. Germs on your hands can infect you or others. Regular hand-washing can help protect you from getting sick.
• Do not touch your face. Avoid touching your eyes, nose and mouth with unwashed hands.
• Check in with your physician and get vaccinated. Regular exams, screenings and vaccinations can help prevent illness and complications from common viruses.

By taking the appropriate steps, you may be able to prevent catching and spreading viruses. Learn more about symptoms of the cold, flu and COVID-19, and how vaccines can protect you.