Snow is falling from the air, so you know what that means — cold and flu season!
Traditionally, the upswing in cases of the cold and flu during the winter has been attributed to dry air and more time being spent indoors, but a recent study added a new culprit.
Researchers from Harvard Medical School at Mass Eye and Ear and Northeastern University have concluded that colder temperature inhibits the immune response within the nose that fights off respiratory illnesses. The study was published on Dec. 6 in the Journal of Allergy and Clinical Immunology.
“Conventionally, it was thought that cold and flu season occurred in cooler months because people are stuck indoors more where airborne viruses could spread more easily,” explained Benjamin Bleier, senior author of the study and HMS associate professor of otolaryngology head and neck surgery at Mass Eye and Ear and senior author of the study. “Our study, however, points to a biological root cause for the seasonal variation in upper respiratory viral infections we see each year, most recently demonstrated throughout the COVID-19 pandemic.”
Why is the nose so important?
The nose is on the first line of defense against pathogens trying to enter the body. It fights them off with an immune response triggered by the entrance of bacteria, according to a 2018 study also conducted by Bleier.
Cells at the front of the nose are activated and release billions of tiny fluid-filled sacs, called extracellular vesticles, which surround and destroy the bacteria. The vesticles also help to shuttle antibacterial proteins from the front to the back of the nose to protect other cells and prevent bacteria from getting farther into the body.
As Bleier told CNN, “EVs can’t divide like cells can, but they are like little mini versions of cells specifically designed to go and kill these viruses. EVs act as decoys, so now when you inhale a virus, the virus sticks to these decoys instead of sticking to the cells.”
The extracellular vesticles are then expelled from the body by mucus (snot), with the bacteria stuck to them. The more decoys, the better the chance of stopping the bacteria before it can make the body sick.
What does the study tell us about the body’s immune response?
In order to test the strength of the vesticles, the team led by Di Huang, research fellow in otolaryngology at Mass Eye and Ear, took four participants from a room of about 74 degrees Fahrenheit and exposed them to 39.9 degree Fahrenheit temperatures for 15 minutes.
The researchers found that the temperature inside the volunteer’s nose had decreased by nine degrees and the number of vesticles had been reduced by 42%, along with a compromise to their effectiveness. They also saw an impairment to the antibacterial proteins.
The team believes this to be a scientific breakthrough. “To our knowledge, Bleier said, “this study is the first to offer a biological explanation for why people are more likely to develop upper respiratory infections like cold, flu, and COVID-19 in colder temperatures.”
They hope that the study’s findings can be used to create new pharmaceuticals — such as drug therapies and nasal sprays that can increase the number of extracellular vesticles and strengthen them.
Mansoor Aniji, distinguished professor of pharmaceutical sciences at Northeastern University, said, “We’ve uncovered a new immune mechanism in the nose that is constantly being bombarded, and have shown what compromises this protection. The question now changes to how can we exploit this natural phenomenon and recreate a defensive mechanism in the nose and boost this protection, especially in colder months.”