You’ve likely heard the saying, “Don’t go outside with wet hair in the winter, or you’ll catch a cold.” While this may sound reasonable, it’s not quite true. The reality is more nuanced. Being cold doesn’t directly cause a cold, but cold weather does make it easier to catch respiratory viruses like the common cold and flu. In fact, lower temperatures are linked to higher COVID-19 rates.
As a nursing professor with a background in public health, I often get asked about the connection between cold weather and the spread of infectious diseases. Let’s explore what actually happens.
Why Cold Weather Increases the Spread of Viruses
Many viruses, including rhinovirus (which causes the common cold), influenza, and SARS-CoV-2 (the virus responsible for COVID-19), thrive in colder temperatures and low humidity. In cold weather, these viruses remain active longer and reproduce more quickly. Additionally, during winter, people tend to spend more time indoors, in closer proximity to others, increasing the chances of germs spreading.
While the flu and respiratory syncytial virus (RSV) have clear seasonal peaks in fall and winter, COVID-19 doesn’t follow the same pattern. New variants and waning immunity have led to COVID-19 surges even during warmer months.
How Cold Weather Affects Virus Transmission
Cold air can alter the outer membrane of the influenza virus, making it more solid and rubbery. This changes how easily the virus spreads from person to person. Dry winter air also plays a role. It helps the influenza virus remain infectious for longer periods. Dry air causes respiratory droplets to evaporate more quickly, creating smaller particles that can travel farther and linger in the air.
Additionally, when you breathe in cold air, it can impair your immune system’s ability to respond effectively. Wearing a scarf over your nose and mouth can help by warming the air before it enters your lungs, making it easier for your immune system to defend against viruses.
Reduced Sunlight and Physical Activity
Winter also means less sunlight, which reduces your vitamin D intake. Vitamin D is crucial for immune health. Furthermore, people tend to be less physically active during colder months, which can impact overall health. Exercise levels often drop due to icy or snowy conditions, but staying active is essential for immune function.
Indoor Contact and Dry Mucous Membranes
In winter, people are more likely to stay indoors, leading to increased close contact with others. This can result in a higher spread of respiratory viruses, which typically transmit within a 6-foot radius.
Cold weather and low humidity can also dry out your eyes and the mucous membranes in your nose and throat. Since viruses are usually inhaled, this makes it easier for them to attach to dry, weakened respiratory passages.
How to Stay Healthy During Winter
While being cold or wet won’t directly make you sick, there are several strategies to help prevent illness:
- Wash your hands often.
- Avoid touching your face, as people do it frequently (9 to 23 times per hour).
- Stay hydrated – aim for eight glasses of water a day, adjusting based on lifestyle and size.
- Eat a well-balanced diet, rich in immune-boosting foods like leafy greens and foods high in vitamin D (eggs, fortified milk, salmon).
- Stay physically active, even during the winter months.
- Get enough sleep to help your immune system stay strong.
- Clean high-touch surfaces in your home regularly.
- Use a humidifier if your nose or throat becomes dry.
- Get your flu and COVID-19 vaccines annually.
By following these tips, you can keep yourself healthy during the winter season and reduce your risk of illness.
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