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The flu season arrives so predictably, and affects so many of us, that it's hard to believe that scientists have had very little idea why cold weather helps germs to spread.
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the answer may have been lying invisible in the air that we breathe. Thanks to the laws of thermodynamics, cold air can carry less water vapour before it reaches the "dew point" and falls as rain. So while the weather outside may seem wetter, the air itself is drier as it loses the moisture. And a steady stream of research over the past few years has shown that these dry conditions seem to offer the perfect environment for the flu virus to flourish.
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That's counter-intuitive – we normally think that the damp makes us ill, rather than protects us from disease. But to understand why, you need to grasp the peculiar dynamics of our coughs and sneezes. Any time we splutter with a cold, we expel a mist of particles from our nose and mouths. In moist air, these particles may remain relatively large, and drop to the floor. But in dry air, they break up into smaller pieces – eventually becoming so small that they can stay aloft for hours or days. (It's a bit like the mist you get when you turn a hose pipe to its finest spray.) The result is that in winter, you are breathing a cocktail of dead cells, mucus and viruses from anyone and everyone who has visited the room recently.What's more, water vapour in the air seems to be toxic to the virus itself. Perhaps by changing the acidity or salt concentration in the packet of mucus, moist air may deform the virus's surface, meaning that it loses the weaponry that normally allows us to attack our cells. In contrast, viruses in drier air can float around and stay active for hours – until it is inhaled or ingested, and can lodge in the cells in your throat.
(Score: 5, Interesting) by frojack on Tuesday October 20 2015, @07:37PM
but it's rather dry in terms of relative humidity for 9 months out of the year.
Relative humidity isn't the important measurement here.
What matters is absolute humidity, grams of water per cubic meter of air.
The more water molecules in the air, the more chance encounters with water a virus particle may have.
Even with LOW relative humidity, you can have a LOT more actual water molecules in the air than some place where its 40 degrees cooler. So at this minute its 78F in Phoenix and 43% relative humidity, but that still allows somewhere between 15 and 25 grams of water per cubic meter of air.
In freezing weather, even with 100% relative humidity you typically only have 5 grams of water molecules per cubic meter of air for a virus particle to bump into.
That's a lot less chance for the water molecules to mess up the virus.
No, you are mistaken. I've always had this sig.
(Score: 0) by Anonymous Coward on Tuesday October 20 2015, @08:01PM
People are usually interacting with each other inside, not outside when it is cold though.
(Score: 2) by slinches on Tuesday October 20 2015, @09:51PM
That's interesting. It's the water vapor itself that interacts with the virus? I figured it would need to condense to have any effect.
That would make more sense as far as flu data goes. Although, in arid climates, the total water vapor content is closely coupled to air temps, so it would be difficult to isolate those effects. That could explain why they weren't addressed (to focus on climates where it would be easier to isolate temp and total humidity).