Why Viruses Prefer a Cold Nose

It's cold outside in many parts of the country today — and that's just right for common cold viruses.
New research from Yale University School of Medicine shows that most rhinoviruses reproduce more efficiently in the cooler temperatures found inside the nose (on cold days) than at core body temperature.

While it has been known that common cold viruses prefer the cooler environs of the nose, this new research explains that behavior by showing that the body’s antiviral immune response is lower in the cooler nose cavity than in the lungs where it’s warmer.
The team, led by senior author and Yale professor of immunobiology Akiko Iwasaki, conducted their research on cells extracted from the airways of mice. Airway epithelial cells, the cells that form the lining of the nose and the other airways, are the main target of rhinovirus infection. In order to spread and cause disease, the virus must enter these cells and make more copies of itself.
The Yale team analyzed how well the immune response performed in cells that were incubated in the typical 33-35-degree C (91-95 F) environment of the nasal cavity, compared with cells that were held in the 37-degree C (98.6 F) temperature that's typical of the lungs.

They found that when a virus invaded warmer cells, they produced more interferons -- proteins that help block the spread of a virus by warning healthy cells and setting off an immune response. In the cooler nasal cavity cells, this warning system was less efficient and the virus was able to spread more easily.
The finding, published in this week's Proceedings of the National Academy of Sciences, reaffirms the age-old motherly advice -- if you're feeling under the weather, don't linger in the cold. Go inside, eat soup, stay warm.