Punctual as the only holiday week on the calendar, the cold has spoiled the holidays for many people in these summer days. But once it is excluded that it is covid, the question remains: how is it possible to contract a cold if it is hot and you are always outdoors? Shouldn’t we get less sick in the summer? Why then does it seem to be happening more than usual this year?
Social life. While influenza and Syncytial Respiratory Virus (RSV) typically strike in the winter, favored by cold weather and indoor hangouts, other viruses that cause symptoms of a cold, such as enteroviruses and type 3 parainfluenza virus, are more common in late summer. and in early autumn, when it is still hot and very humid. The reasons are manifold. In the summer months we travel more, meet many more people from different locations, attend concerts and nightclubs, cool off in places with maximum air conditioning, all factors that favor viral transmission.
invisible protections. The structure of viruses, which allows pathogens to survive outside and inside the human body and to use our cells to make copies of their genetic code, also plays its part. As explained on The Conversationviruses are surrounded by a protein envelope called capsid. But some also have a lipid shield that shields them from attack by the immune system and facilitates cellular infection. These viruses are called “coated” and are more vulnerable to heat and humidity.
Many winter viruses belong to this group, which therefore survive better in a cold and dry climate. Conversely, some summer viruses that cause colds (such as enteroviruses) do not have this coating. Others, like the parainfluenza virus type 3, have it but prefer high temperatures as well low humidity. In short, the structure of the virus alone does not explain everything.
Defenses and thermometer. Another factor at play could be the role that high temperatures have on the immune system. Some studies in mice associate exposure to temperatures of 36 ° C and more with a lower immune response. It is unclear whether the same holds true for humans.
Covid effect. There are also specific reasons l’estate 2022. The pandemic caused restrictions on travel, interactions and viral exposure also last summer: in the 2021 holidays many of us wore the mask in contexts at risk of covid, thus also limiting encounters with other pathogens. Immunity to seasonal viruses is short-lived, so more people today find themselves vulnerable to their attack and cold. CoViD-19 also, as we know, altered the predictability of the occurrence of other viral infections.
Torrid summer. Finally, this year turned out to be exceptionally hot. Many areas of the Northern Hemisphere have been struggling with record temperatures and heat waves, which in addition to favoring drought have facilitated viral transmission and the emergence of diseases typical of tropical latitudes. Climate change is already making pathogens more virulent and promoting their circulation.