Scientists have found a compelling explanation for why more respiratory illnesses occur in winter, according to a new study.
In the study, which was published Tuesday in The Journal of Allergy and Clinical Immunology, researchers found that cold air can damage the immune response in the nostrils. Reducing the temperature inside the nose by as little as 9 degrees may kill nearly 50% of the virus and bacteria-fighting cells in the nostrils.
"This is the first time that we have a biologic, molecular explanation regarding one factor of our innate immune response that appears to be limited by colder temperatures," Dr. Zara Patel, professor at Stanford University School of Medicine in California, told CNN.
"Cold air is associated with increased viral infection because you've essentially lost half of your immunity just by that small drop in temperature," added rhinologist Dr. Benjamin Bleier, director of otolaryngology at Massachusetts Eye and Ear and an associate professor at Harvard Medical School in Boston.
The study, however, has limitations. Scientists conducted in vitro studies which means, as Patel explained to the outlet, human tissue in the lab was used to study the immune response, instead of a study with humans.
"Often the findings of in vitro studies are confirmed in vivo, but not always," she noted.
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Respiratory illnesses have skyrocketed in recent months. Last month, the Health and Human Services Department revealed that the country saw a 30% increase of flu hospitalizations.
More than 11,200 people were hospitalized with the flu during the week ending Nov. 19, compared to about 8,700 people hospitalized the week before. Health experts also believe flu hospitalizations will rise even more leading up to Christmas and New Year's Eve travel.
The CDC states that about 11 of every 100,000 people have been hospitalized with the flu since October, which is the highest in the past decade. Additionally, at least 6.2 million flu illnesses have been reported this season, along with 53,000 flu-related hospitalizations and 2,900 flu-related deaths.
"The fact that we're already at this high level going into the holiday season makes me nervous," Scott Hensley, microbiologist and flu expert at the Penn Institute for Immunology, told CNBC, noting that people should stay up to date with their vaccines.
"From what we can see, it looks like the vaccines are pretty darn good matches to what's circulating," he added. "If there's ever a time to get vaccinated, this is the year to do it."