# What is the science of catching a cold/getting flu?



## conscius (Apr 20, 2010)

I've heard this advice that during flu season, avoid crowded places because you're more likely to catch something from close contact with a sick person. Apparently you don't catch anything from being out in the cold, that viruses can mainly be transmitted through another person. That makes no sense. Where did those people catch it, in other crowded places? And then those...? 

p.s.Couldn't decide if put in health section or not, but this is about science of spread of germs, not getting fit or healthy, so put it here.


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## Dao (Sep 13, 2013)

I don't know how these viruses evolved and came into being but they can only be transmitted through droplets when patients cough, sneeze and so on. It does not make sense that anyone would contract a cold virus due to cold weather any more than it makes sense that cold weather causes bacterial infections. You have to pick up these viruses from infected patients and infected surfaces.


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## conscius (Apr 20, 2010)

Shimmerleaf said:


> I don't know how these viruses evolved and came into being but they can only be transmitted through droplets when patients cough, sneeze and so on. It does not make sense that anyone would contract a cold virus due to cold weather any more than it makes sense that cold weather causes bacterial infections. You have to pick up these viruses from infected patients and infected surfaces.


Thanks for answering my question. Is it just your opinion or are you a bio major or something? Cause I just want to make sure I got this right: 

So somebody touches a surface that has a virus on it. And for some reason in winter, those particular kind of virus that give us cold are more present or perhaps we're more vulnerable towards them? Then this person puts their hand in their mouth, "catch a cold", then walk around coughing and sneezing. And now the virus is somehow more potent than before, because it's airborne or because somehow through the person getting sick it has gained some more power to make others ill?


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## Dao (Sep 13, 2013)

conscius said:


> Thanks for answering my question. Is it just your opinion or are you a bio major or something? Cause I just want to make sure I got this right:
> 
> So somebody touches a surface that has a virus on it. And for some reason in winter, those particular kind of virus that give us cold are more present or perhaps we're more vulnerable towards them? Then this person puts their hand in their mouth, "catch a cold", then walk around coughing and sneezing. And now the virus is somehow more potent than before, because it's airborne or because somehow through the person getting sick it has gained some more power to make others ill?


I am simply a curious individual who winds up seeing the doctor a lot! But what I said is easily corroborated on Google.

There are numerous theories why there is a cold season, including that people tend to stay indoors during cold weather, which facilitates coming into more contact with infected persons and surfaces. The back-to-school season also plays this part. I'm under the impression that unfortunately colds are still poorly understood. I thought these were interesting though:

Why Do People Seem To Get More Colds In The Winter?

FYI: Why Is there a Winter Flu Season?


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## conscius (Apr 20, 2010)

Shimmerleaf said:


> I am simply a curious individual who winds up seeing the doctor a lot!


Oh I'm sorry. Funny, recently I've become worried about little things like that, like catching a cold. Never thought about it in the past, just went about my day, if I caught it, so be it, couple days of sniffing and sneezing and some body pain, then gone. But now I see people coughing and kind of try to escape. Don't know why.

Anyhow, thank you for the subsequent answer and links.


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## Dao (Sep 13, 2013)

conscius said:


> Oh I'm sorry. Funny, recently I've become worried about little things like that, like catching a cold. Never thought about it in the past, just went about my day, if I caught it, so be it, couple days of sniffing and sneezing and some body pain, then gone. But now I see people coughing and kind of try to escape. Don't know why.
> 
> Anyhow, thank you for the subsequent answer and links.


No problem! I hope you stay well too. I've been washing my hands religiously now and carrying wet wipes and they've helped a ton.


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## Gossip Goat (Nov 19, 2013)

You get infected with the virus or bacteria. That starts wreaking havoc in your body and you start showing symptoms because of what the invader is doing.

As for the temperature thing, a doctor told me colder temperature reduces your body's immune system and makes you slightly more prone to getting sick.


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## VinnieBob (Mar 24, 2014)

supposedly winter born illness is caused my lack of vitamin D
vitamin D is produced when one is exposed to prolonged periods of sunlight
i have never cared for that theory, just never clicked with me
i believe ultra violet light kills the agent responsible for the illness


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## zynthaxx (Aug 12, 2009)

conscius said:


> I've heard this advice that during flu season, avoid crowded places because you're more likely to catch something from close contact with a sick person. Apparently you don't catch anything from being out in the cold, that viruses can mainly be transmitted through another person. That makes no sense. Where did those people catch it, in other crowded places? And then those...?
> 
> p.s.Couldn't decide if put in health section or not, but this is about science of spread of germs, not getting fit or healthy, so put it here.


Common cold - Wikipedia, the free encyclopedia

It makes a lot of sense that you don't catch virus- or bacteria based illnesses solely from being out in the cold. So yes, the person who infected you got infected by someone else and so on in an unbroken chain that goes back to when the infecting agent evolved in a way that made humans susceptible to it.


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## HAL (May 10, 2014)

Yeah the cold is said to reduce your immune system. I'd be willing to believe it. Bodily processes slow down, blood is primarily focussed on keeping you warm, rather than keeping you properly immune.

I learned about the flu virus at school.

It sets in your throat and goes from there. Hence it begins to hurt to swallow, you get the sore throat and then all the other bits happen after. This is also why you have an annoying and fairly severe tickly cough in the last stages of recovery. Your body ejects the bits of your throat that the virus settled into.

Disclaimer: I could be wrong but that is seriously what I learned in school.

Also I'm curious about whether you're talking about the general common cold, or actual influenza. The common cold is of course dependent on the immune system which we largely agree is weaker in cold conditions. Influenza is similar but is actually much less common. People who complain of having flu are often just suffering from a bad cold. Real influenza is the real deal, aching joints, intense fever, zero appetite, weight loss. It lasts about a week and you absolutely cannot leave your bed, you can't go to work and be all, "Oh god I've got the flu." . Influenza is several orders of magnitude worse than the common cold. Some people haven't even had it before.

From wikipedia:



> The most common symptoms include: a high fever, runny nose, sore throat, muscle pains, headache, coughing, and feeling tired. These symptoms typically begin two days after exposure to the virus and most last less than a week. *The cough, however, may last for more than two weeks*


Most people with 'the flu' aren't that bad. And I certainly don't see all these flu-ridden people coughing away afterwards!

Ok side-rant over :happy:


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## ALittleEquilibrium (Apr 23, 2015)

Some people have a naturally weakened immune system due to chronic illness, medications, or other things out of their control. This means they pick up germs more easily than others. I just had a month-long bout with sinusitis.


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## FearAndTrembling (Jun 5, 2013)

Cold weather dries people out. There is a drop in humidity. This is why people often get dry and itchy skin in the winter. We also have indoor heating systems which dry us out. 

Never touch your face. That is where most get in. Eyes. Nose. Mouth. A major reason people are more susceptible to colds in the winter, is dryness. The inside of your nose dries out, and can get tiny cracks that viruses can wiggle their way into. 

Viruses also like dryness better. They can live in it longer. A guy can sneeze and that stuff can hang in the air for days maybe.


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## FourLeafCloafer (Aug 5, 2014)

conscius said:


> I've heard this advice that during flu season, avoid crowded places because you're more likely to catch something from close contact with a sick person. Apparently you don't catch anything from being out in the cold, that viruses can mainly be transmitted through another person. That makes no sense. Where did those people catch it, in other crowded places? And then those...?
> 
> p.s.Couldn't decide if put in health section or not, but this is about science of spread of germs, not getting fit or healthy, so put it here.


Being in the cold _can_ weaken your immune system by making you expend more energy on staying warm, but we get viruses and bacteria from other people, they don't just blip into existence. Yeah, a bacterium might survive for a while on a surface that was touched or coughed on by a sick person, but direct contact with the person is way more risky. (viruses generally don't survive long outside the host body.) Not everybody who is contagious acts 'sick'. Most people carry a small amount of bacteria and viruses inside their body that they don't get sick from, but that can make others sick. 

In winter, people come together in groups more, because we are inside more, and we like to be cozy. Don't forget Christmas: How many people do you meet in the holiday season that you aren't in contact with much otherwise? All those parties are a good way for new strains of illnesses to spread. The quick changes between heat inside and cold outside are hard for our bodies to deal with.


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## Miharu (Apr 1, 2015)

Germs and viruses make you sick, not the cold weather itself. It's usually the case because dry winter air allows the virus to thrive. To get sick, you'd have to get infected by viruses (which you can easily get from anyone, as I'm sure you know).

Then there comes the symptoms, to alert you that you're not well. Then the medicine, which does not exactly kill the virus, but rather give you a bit of a relief while your body is naturally working to fight it off.


And no, not a doctor, not a nurse. Just a tiny bit of a health freak.


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## FearAndTrembling (Jun 5, 2013)

stultum said:


> Being in the cold _can_ weaken your immune system by making you expend more energy on staying warm, but we get viruses and bacteria from other people, they don't just blip into existence. Yeah, a bacterium might survive for a while on a surface that was touched or coughed on by a sick person, but direct contact with the person is way more risky. (viruses generally don't survive long outside the host body.) Not everybody who is contagious acts 'sick'. Most people carry a small amount of bacteria and viruses inside their body that they don't get sick from, but that can make others sick.
> 
> In winter, people come together in groups more, because we are inside more, and we like to be cozy. Don't forget Christmas: How many people do you meet in the holiday season that you aren't in contact with much otherwise? All those parties are a good way for new strains of illnesses to spread. The quick changes between heat inside and cold outside are hard for our bodies to deal with.


There was a study last year on cold weather speeding up your metabolism too. Which makes sense. Your body has to work to stay warm. 

In the journal _Trends in Endocrinology and Metabolism_, scientists from Maastricht University in The Netherlands argue that when exercise isn't an option, "regular exposure to mild cold may provide a healthy and sustainable alternative strategy for increasing energy expenditure."

Shivering can increase your metabolic rate as much as five fold. The problem with shivering is that it is terrible, so Dr. Wouter van Marken Lichtenbelt and colleagues looked into being only mildly cold as a way to burn calories. Our bodies burn energy to keep us warm in a process called non-shivering thermogenesis (NST), they explain, which works even at pretty reasonable temperatures. They defined mild cold exposure as 64 degrees Fahrenheit.


"In most young and middle-aged people NST increases by between a few percent and 30 percent in response to mild cold exposure," they write. They say that can significantly improve your calorie-in to calorie-burned ratio. Even if you eat more to compensate, most people won't eat enough to undo the extra expenditure.

How Being Cold Burns Calories - The Atlantic


Poor allergy maintenance is another thing that can lead to colds. And anxiety. Suppresses the immune system.


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