Researchers have found cold temperatures may diminish an immune response in the nose, a possible explanation for why upper respiratory infections are more common in cold weather.
"Conventionally, it was thought that cold and flu season occurred in cooler months because people are stuck indoors where more airborne viruses could spread more easily," Benjamin Bleier, MD, senior study author and professor of otolaryngology head and neck surgery at Harvard Medical School in Boston, said in a Dec. 5 news release. "Our study, however, points to a biological root cause for the seasonal variation in upper respiratory viral infections we see each year," Dr. Bleier said.
Previous research has found cells in the nose release billions of extracellular vesicles, known as EVs, when bacteria are detected. The EVs are tiny fluid-filled sacs that swarm and attack the bacteria. The latest study, led by Di Huang, PhD, a research fellow in otolaryngology at Harvard, found a similar immune response also kicks in when common cold and flu viruses enter the nose. However, the findings, published Dec. 6 in the Journal of Allergy and Clinical Immunology, indicate the immune response was blunted in cold temperatures.
Among participants who were exposed to cold temperatures, researchers found the number of EVs released by the nasal cells fell by 42 percent. Antiviral proteins within the EVs were also impaired.
"Combined, these findings provide a mechanistic explanation for the seasonal variation in upper respiratory infections," Dr. Huang said.
View the full study here.