We finally know why we get more colds and flu in the winter

We finally know why we get more colds and flu in the winter

 

A chill is in the air, and you know what that means: It's time for cold and flu season, when it seems everyone you know is suddenly sneezing, sniffling or worse. It's almost as if those pesky cold and flu germs whirl in with the first blast of wintry weather.   Yet germs are present year-round. Just think back to your last summer cold. So why do people get more colds, flu and now Covid-19 when it's chilly outside?   The scientists behind a new study may have found the biological reason we get more respiratory illnesses in winter. It turns out the cold air itself damages the immune response going on in the nose.   To understand why this happens, the researchers went on a scientific detective hunt.   A respiratory virus or bacteria invades the nose, the main point of entry into the body. Immediately, the front of the nose detects the germ, well before the back of the nose is aware of the intruder, the team discovered.   At that point, cells lining the nose begin creating billions of simple copies of themselves called extracellular vesicles, or EVs.   "EVs can't divide like cells can, but they are like little mini versions of cells specifically designed to go and kill these viruses," said rhinologist and study co-author Dr. Benjamin Bleier. "EVs act as decoys, so now when you inhale a virus, the virus sticks to these decoys instead of sticking to the cells."   Those "Mini Mes" are then expelled into nasal mucus (yes, snot), where they stop invading germs before they can get to their destinations and multiply.   When under attack, the nose increases production of extracellular vesicles by 160%, the study found. There were additional differences: EV's had many more receptors on their surface than original cells, thus boosting the virus-stopping ability of the billions of extracellular vesicles in the nose.   So the nose comes to battle armed with some extra superpowers. But what happens to those advantages when cold weather hits?   Reducing the temperature inside the nose by as little as 9° Fahrenheit (5° Celsius) kills nearly 50% of the billions of virus- and bacteria-fighting cells in the nostrils, according to the study.   What does that do to your ability to fight off colds, flu and Covid-19? It cuts your immune system's ability to fight off respiratory infections by half, Bleier said.