why do we catch colds in winter
Why do we get more colds and coughs in autumn and winter? I seem to remember something about the condensation carrying germs around in little 'germ packets', but I'm not sure if I didn't make that up myself. The most likely explanation is that in summer people are more likely to be out and about. In winter we all get away from the cold weather into confined spaces with air heating system which recirculate the air from those who have the virus which causes the cold. One theory is the decrease in ultraviolet light during the winter due to shortened daylight. Viruses are very sensitive to UV light as it destroys their DNA; less UV in winter, more viruses. Though decreased ventilation effectively increases the amount of virus in the air, since viruses causing respiratory disease are passed in water vapour we cough and sneeze from the respiratory tract, it is easy to breathe in where is starts it life cycle again.
Ideal conditions to produce billions of virus particles
My partner's psychologist says that colds are a physical manifestation of a psychological problem. In years gone by, winter would be the time for people, who worked in tune with seasons and nature, to rest up having got in the crops in autumn. That, together with decreased daylight hours would make winter a time for increased rest and longer sleep. Now that we force our bodies to work longer and longer hours against nature, colds are our bodies way of forcing us to rest. Since we can't take days off merely to stay in bed, our body makes us sick so we have an excuse to stay home and sleep. Could it be something to do with the reduction of sunlight causing a depression of the immune systems? I think most research suggests that cold viruses are transmited by hand to mucus membrane.
You wipe your nose, shake someone's hand and then they rub their eyes and are infected. So any explanation that involves ventilation/heating systems or condensation is suspect. The most likely explanation is that winter sees larger groups of people gathered together in close proximity leading to much higher infection rates. I think so this happens just because of the air pressure in the air. HealthDay Reporter TUESDAY, Jan. 6, 2015 (HealthDay News) -- Though it's never been scientifically confirmed, conventional wisdom has it that winter is the season of sniffles. Now, new animal research seems to back up that idea. It suggests that as internal body temperatures fall after exposure to cold air, so too does the immune system's ability to beat back the rhinovirus that causes the. "It has been long known that the rhinovirus replicates better at the cooler temperature, around 33 Celsius (91 Fahrenheit), compared to the core of 37 Celsius (99 Fahrenheit)," said study co-author Akiko Iwasaki, a professor of immunobiology at Yale University School of Medicine. "[But] the reason for this cold temperature preference for virus replication was unknown.
Much of the focus on this question has been on the virus itself. However, virus replication machinery itself works well at both temperatures, leaving the question unanswered," Iwasaki said. "We used mouse airway cells as a model to study this question [and found that] at the cooler temperature found in the nose, the host immune system was unable to induce defense signals to block virus replication," Iwasaki explained. The researchers discuss their findings in the current issue of the Proceedings of the National Academy of Sciences.
To explore the potential relationship between internal body temperatures and the ability to fend off a virus, the research team incubated mouse cells in two different temperature settings. One group of cells was incubated at 37 C (99 F) to mimic the core temperature found in the, and the other at 33 C (91 F) to mimic the temperature of the nose. Then they watched how cells raised in each environment reacted following exposure to the rhinovirus. The result? Fluctuations in internal body temperatures had no direct impact on the virus itself. Rather, it was the body's indirect immune response to the virus that differed, with a stronger response observed among the warmer lung cells and a weaker response observed among the colder nasal cells. And how might outdoor temperatures affect this dynamic?
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