It's wintertime, a time when cold weather usually hails in the cold and flu season as well. And a new study supports this notion, finding that the common cold virus runs more rampant in cooler temperatures.
Researchers have long known that the rhinovirus, the most frequent cause of the common cold, can replicate itself more efficiently in the cooler conditions of the nose than at core body temperature, say in the warmer lungs. But until now, their focus was on how body temperature influenced the virus rather than our body's immune system.
This study, published in the journal Proceedings of the National Academy of Sciences, aims to investigate this poorly studied relationship.
To better investigate, study senior author Akiko Iwasaki and a team of Yale researchers examined the cells taken from the airways of mice. They compared the immune response to rhinovirus when cells were kept at 37 degrees Celsius (98.6 Fahrenheit) - or core body temperature - and at the cooler 33 C (91.4 F).
"We found that the innate immune response to the rhinovirus is impaired at the lower body temperature compared to the core body temperature," Iwasaki, a professor of immunobiology at Yale University, said in a statement.
According to the researchers, the body's immune response also plays a part in how rapidly the rhinovirus replicates, rather than temperature influencing the virus alone. They observed, for example, in mice with genetic deficiencies related to the immune system that the cold virus could better replicate at the higher, core body temperature. This is because the immune system is responsible for detecting viruses and initiating an antiviral response. Deficiencies in this mechanism therefore led to the virus' persistence.
"That proves it's not just virus intrinsic, but it's the host's response that's the major contributor," Iwasaki explained.
Although the immune system of mice no doubt is different from our own virus-fighting mechanisms, the study provides insight that may help humans fight off the common cold. After all, about 20 percent of us harbor the rhinovirus in our nasal cavities at any given time.
"In general, the lower the temperature, it seems the lower the innate immune response to viruses," noted Iwasaki, so be sure to bundle up and keep warm this winter if you want to avoid catching a cold.
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