London, Europe Brief News – Winter is traditionally boom times for respiratory viruses—a point well proven by this year’s confluence of influenza, RSV, and COVID-19.
Almost 9 million people nationwide have been sickened by the flu already this season, RSV is surging among children, and COVID-19 continues to infect tens of thousands of people in the U.S. each day.
But why does cold weather typically translate to cold and flu season during winter?
Experts often point to changes in human behavior—namely that chilly temperatures force people inside, where it’s easier for germs to spread. But a new study published in The Journal of Allergy and Clinical Immunology suggests another explanation can be found within our noses.
As the body’s gateway to the outside world, the human nose is equipped with defenses meant to stop invaders, such as viruses and bacteria, in their tracks. In 2018, researchers from Boston’s Northeastern University, Massachusetts Eye and Ear (a teaching hospital affiliated with Harvard Medical School), and several other organizations described one of those shields in a paper also published in The Journal of Allergy and Clinical Immunology. When the nose detects bacteria, they found, it releases a swarm of tiny fluid-filled sacs meant to attack and neutralize it.
“When you kick a hornet’s nest, the hornets swarm out and try to kill whatever the attacker is before it can attack the nest,” says co-author Dr. Benjamin Bleier, director of otolaryngology translational research at Massachusetts Eye and Ear. “That’s what the body’s doing.”
In the new study, Bleier and his collaborators show that the nose deploys similar defenses against common respiratory viruses, including two rhinoviruses (frequent causes of the common cold) and a coronavirus (though not the one that causes COVID-19). They also set out to answer another question: does cold weather dampen the effectiveness of the nose’s natural immune response?
Previous research suggests common respiratory viruses thrive at lower temperatures. In 2015, a research team from Yale University used mice to demonstrate that rhinoviruses are better at replicating in colder temperatures because antiviral immune responses aren’t as strong under these conditions. Research from the National Institutes of Health has also shown that influenza viruses are better at spreading in chilly climates.
