In winter, we catch colds and respiratory diseases more often – this is common knowledge, but the reasons for this phenomenon have so far remained a mystery to scientists. The answer was provided for the first time by the latest research of American scientists. A mechanism has been discovered that causes our immunity to weaken at low temperatures.
The research results were published in the Journal of Allergy and Clinical Immunology on December 6. Scientists believe they have found the first biological explanation for why respiratory illnesses like colds, flu and COVID-19 are more common when the temperature drops.
“Traditionally, cold and flu season was thought to occur in the colder months because people spend more time indoors, where airborne viruses can spread more easily,” study co-author Benjamin Bleier told the Independent. “Our study, however, points to a biological cause for the seasonal variability of upper respiratory viral infections that we see each year,” he noted.
Why is it easier to catch a cold in winter?
Benjamin Bleier in 2018 discovered a previously unexplored reaction of the immune system responsible for fighting bacteria. He determined that cells in the front of the nose detect them and then in response release billions of microscopic extracellular transport vesicles (EVs) into the nasal mucus that surround and attack the detected bacteria. Now a group of scientists from Boston’s Northeastern University and a specialist hospital in Massachusetts decided to check whether a similar reaction occurs in the case of viruses responsible for diseases of the upper respiratory tract.
For this purpose, they studied how the cells in the nose respond to contact with three types of viruses: COVID-19 and two rhinoviruses that cause the common cold. Although the immune response of the body was slightly different from the one observed in 2018, each of the viruses applied, as expected, resulted in increased production of EVs follicles.
However, as it turned out, this reaction is blocked when the temperature drops. At 5 degrees Celsius, the amount of EVs secreted by nasal cells decreased by almost 42 percent. The EVs themselves were also attenuated. As reported, 5 degrees is the temperature inside a person’s nose for 15 minutes at 4.4 degrees Celsius. It is this phenomenon of blocking the reaction to contact with viruses at low temperature that is to be the direct cause of more frequent illnesses in the winter.
Study leader Di Huang, who led the study, told the Independent that the findings from both findings provide a better understanding of the seasonality observed in the upper respiratory tract. In the future, they may also contribute to the development of agents that increase resistance to winter colds.
Journal of Allergy and Clinical Immunology, Independent
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