why do we get more colds in the winter

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? As the days get shorter and the temperatures get lower, it seems that the chance of getting a cold increases.


The вcommon coldв does indeed seem more common in the winter. Several factors make the winter season a hotbed for the cold virus, and our behaviour in the colder months may have something to do with it. В В В В В В When the temperatures drop outside, we find ourselves spending more time inside, with the doors and windows closed. This poor ventilation means that germs remain in the air, as there is nowhere for them to escape to. The cold weather also means that we are more likely to take public transport, and so find ourselves in confined areas in close proximity to others who are coughing and spluttering. Areas that are regularly touched by hands like door knobs, keyboards and rails are havens for germs, and the more time we spend indoors, the more we are exposed to them. The cold weather also affects the body s immune system, as it wears down defences against infection. The shorter days and longer nights of winter mean less sunlight and thus less natural vitamin D which helps power the immune system. This consequently makes us more vulnerable to infection.


The cold virus also transmits faster in the cold. Lower temperatures make its lipid coating tougher, and therefore more resilient and active. Cold air also carries less water vapour than hot air, making it drier. So when we cough and sneeze the mist of particles from our mouth and nose remain in the air for longer; as a result, it is more likely for us to catch the cold virus. Combatting the effects of winter will help reduce the risks of catching a cold. Keep warm by erring on the side of wearing too much clothing. In other words, it is much better to have a hat, gloves and scarf with you just in case you need them, rather than not having them at all. Taking vitamin supplements will help you get your daily recommended intake and keep your immune system strong, so too will getting enough sleep. Drinking plenty of water helps flush out the toxins that accumulate in our bodies, and washing your hands regularly will reduce the likelihood of catching and spreading the cold virus, as will being careful of putting your hands near vulnerable areas like your eyes, mouth and nose.

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