Many of us have heard, "Don't go out without a sweater or you'll get sick (of the flu or a cold)."

That's not exactly true. As with many things, the reality is more complicated.

Here's the distinction: being cold is not the reason you catch a cold. But it is true that cold weather makes it easier to catch a cold or the flu.

It's still too early to know how the weather impacts the COVID-19 virus, but scientists are beginning to think that it behaves differently from cold and flu viruses.

As an Associate Professor of Nursing with a background in public health, I get asked about this all the time. So here's a look at what really happens.

Many viruses, including rhinovirus, the common culprit in the common cold, and influenza, remain infectious longer and replicate faster in cooler temperatures. That is why these viruses spread more easily in winter. Wearing a thick coat won't necessarily make a difference.

Virus transmission is easier when it's cold

More specifically, cold weather can change the outer membrane of the influenza virus; makes the membrane more solid and rubbery. Scientists believe that the rubber coating makes it easier for the virus to spread from person to person.

It's not just cold winter air that causes a problem. Dry air in addition to cold has been linked to flu outbreaks. A study from the National Institutes of Health suggests that dry winter air further helps the influenza virus remain infectious longer.

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How your immune system responds during cold weather is also very important. Inhalation of cold air can negatively affect the immune response in the respiratory tract, making it easier for viruses to take hold. That's why wearing a tissue over your nose and mouth can help.

Also, most people get less sunlight in winter. That's a problem because the sun is a major source of vitamin D, which is essential for a healthy immune system. Physical activity, another factor, also tends to decrease during the winter. People are three times more likely to delay exercise in such conditions.

Instead, people are spending more time indoors. That usually means closer contact with others, which leads to the spread of the disease.

Respiratory viruses generally spread within a two meter radius of an infected person. When you're indoors, you're likely to be closer than that distance.

In addition, cold weather dries out the eyes and the mucous membranes of the nose and throat. Because the viruses that cause colds and flu are usually inhaled, they can attach themselves more easily to these dry, damaged ducts.

What you can do

While the bottom line is that being wet and cold doesn't make you sick, there are strategies to help prevent illness year-round.

*Wash your hands frequently.

*Avoid touching your face, something people do between nine and 23 times an hour.

* Hydrate. Eight glasses of water a day is a good goal, but that could be more or less depending on the person's lifestyle and size.

*Eat a well-balanced diet. Dark green leafy vegetables are rich in vitamins that support the immune system; eggs, fortified milk, salmon, and tuna contain vitamin D.

*Stay physically active, even during the winter.

*Clean hard, high-touch surfaces in your home frequently.

*If your nose or throat gets dry in the winter, consider using a humidifier.

*Get a flu shot.

And one more important thing this year: when it's your turn, make sure you get the COVID-19 vaccine.

The original note can be found here.

Libby Richards, Associate Professor of Nursing at Purdue University, for The Conversation.

*The Conversation is an independent, non-profit source of news, analysis and commentary from academic experts