Every year once more… if your nose runs, your head hurts, if you cough, then it quickly becomes clear that you have a cold.
Researchers in the USA have now found out why we develop this annoying disease in winter.
Im Journal of Allergy and Clinical Immunology The researchers explain why falling temperatures and an increase in respiratory infections are linked to other viruses that cause flu and Covid-19.
Contrary to what you might think, the main reason is not that we spend more time indoors in winter and thus have closer contact with other people.
People primarily become infected via the upper respiratory tract (nose, mouth and throat), either by inhaling the pathogen or by bringing it into the mouth or nose via their hands.
Vesicles in the nose fight off viruses and bacteria
The research team at the Mass Eye and Ear hospital and Northeastern University in America has discovered an immune response in the nose that fights off viruses that cause respiratory infections, for example.
But this immune response, discovered for bacteria in 2018, is blocked in cold temperatures.
Specifically, the scientists discovered that cells in the front part of the nose identify bacteria and viruses, and then billions of tiny so-called extracellular vesicles, or EV for short, “swarm-like” release, which then trap and destroy invading pathogens.
In the earlier study, the researchers were also able to show that the EVs transport protective antibacterial proteins through the mucus from the front of the nose to the back along the airways. There they can protect cells from bacteria before they get too far into the body.
In the test, the researchers then found out that this antiviral defense function is only greatly reduced when exposed to cold. It is therefore easier for viruses and bacteria to penetrate the body.
“Our study provides a direct quantitative mechanistic explanation for seasonal fluctuations in the prevalence of upper respiratory tract infections,” say the researchers.