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I heard "common colds" are more widespread in winter because: - viruses involved tend to remain active longer in colder air - interior air is renewed less fre

I heard "common colds" are more widespread in winter because: - viruses involved tend to remain active longer in colder air - interior air is renewed less frequently in winter, increasing the likelihood to encounter the virus But there is still this very common belief that we get ill by getting cold in a physical sense, while e.g. being outside with not warm enough clothes. Is it that being exposed to cold air makes out defenses in the lungs or nose less efficient? Is it that we are cold because we actually start developing the illness for which we were infected a few days ago? Or is it just a cognitive bias and only the two factors cited above play a role?

nicbou 6y ago
I got curious, because I got a cold or something similar after walking in the snow with wet boots for a few kilometres. It's the second time it happens to me. From what I gather, that makes you more vulnerable to viral and bacterial infections. Adding to that, people spend more time in enclosed spaces in the winter, making exposure more likely.
- legerdemain 6y ago
  It's easily observable that colds are more common in winter (at least in temperate climates where winter is the cold season). I've just always had trouble buying the argument that "people spend more time in enclosed spaces" in winter. At least not a degree significant enough to make a difference. I go to an office and spend the same amount of time in it in the winter and in the summer. Employees at meatpacking plants and Starbucks baristas don't get to work outside in the summertime. Children still go to school, their school days are just as long, and they don't have classes outside even if the weather allows it. You still have to walk the dog, whether it's summer or winter. All the outdoor activities that are easier to do in warmer weather just don't seem to be universal enough to explain effects on a whole population. Most people spend very little time hiking outdoors. As a fraction of the total number of people in the entire country, the number of people who play tennis outdoors is probably tiny. Drinking at the bar versus drinking on an outdoor patio barely seems worth mentioning. Maybe the cold epidemics are driven by agricultural workers who stay indoors in winter? At least they're pretty numerous, there are more of them than there are tennis players...
  - maelito 6y ago
    > I go to an office and spend the same amount of time in it in the winter and in the summer. Employees at meatpacking plants and Starbucks baristas don't get to work outside in the summertime. Children still go to school, their school days are just as long, and they don't have classes outside even if the weather allows it. You still have to walk the dog, whether it's summer or winter. This is very different in my case (France). In the summer, windows are often open, which suffice to make a big difference I believe, work and home. Never in winter. In summer, half or our work meals are eaten outside or in well ventilated restaurants. Winter -> at most you walk fast 2 minutes to get in a hot building again. Social activites are all closed rooms in winter.
    - legerdemain 6y ago
      Ah! What a fascinating world. The parts of the US that I am familiar with make extremely widespread use of indoor climate control. Many buildings, such as offices and schools, have windows that barely open or don't open at all. And even if the weather permits you to eat outdoors, there usually isn't enough public space where you could do it comfortably and safely. I guess you could drive to a restaurant and then eat in your car with the windows rolled down.
      - graeme 6y ago
        Notably the US had high summer covid cases in the AC belt, in contrast to the northeast and also in contrast to canada and europe, where hermetically sealed environments are less common. I’d be curious to know what flu and cold season is like in the south. There may also be seasonal changes to hvac systems in milder climates. They all have varying degrees of recirculation vs bringing in outside air. If you are running heavy ac or heavy heating, it costs more to bring in outside air. So there may be seasonal variations in recirculation settings even within the same sealed environment. I’m less confident on this point though as I don’t know hvac’s very well and they are supposed to filter viruses.
  - maxerickson 6y ago
    Humidity factors into how long many viruses can remain viable. Covid lasts longer in dryer air. Beach trips, playgrounds, etc probably do add up.
- jerome-jh 6y ago
  Not that I want to contradict your experience, it is actually very common. But I would truly be interested in knowing the causality relationship between having the feet wet and cold and having a "common cold", that is an infection of the nose/sinuses/throat/lungs.
  - lultimouomo 6y ago
    It has been suggested that cold reduces flow in the nasal blood vessels and this hinders immune response, giving the virus a foothold for infecting the organism. I read a study about a bunch of people being left with their feet in a pool of cold water and it showed an increased infection rate vs the control group, but I don't remember how significant and I cannot find it anymore.
  - kijin 6y ago
    Your feet have a large blood supply and a large surface area. Getting your feet wet is a very effective way to lower your body temperature.
maelito 6y ago
My bet is that "interior air is renewed less frequently" makes most of the effects. It doesn't look hard to test experimentally.
DownGoat 6y ago
>> But there is still this very common belief that we get ill by getting cold in a physical sense, while e.g. being outside with not warm enough clothes. This is kinda true, the body produce mucus (snot) in the nasal passages. Microbes sticks to this, and when swallowed are neutralized by our stomach acid. But cold air slows down this process, so our first line of defence doesn't work as well during winter. There are also factors such as behaviour changes like spending more time indoors, closed windows and a lot of other stuff that also likely helps spread infections.
- kijin 6y ago
  I think there are multiple factors, each of which only increases R by a little bit, but when combined produce a noticeable increase. Lack of ventilation is certainly a major factor. The temperature difference between indoors and outdoors is much larger in the winter, so people are more reluctant to let in fresh air. We also don't wash winter clothes as often as we do summer clothes, so viruses that stick to fabric might have more chances to get into our bodies. Homes and public spaces get cleaned less often, too, as they don't feel as sticky and smelly as they do in the summer. Ditto for our own hands, which is probably more important that any of the other factors mentioned here. In the United States, two of the largest mass migration and shopping events of the year take place in the early to mid-winter: Thanksgiving and Christmas. In China, COVID-19 began to spread in earnest outside of Wuhan around Chinese New Year. Even societies that don't have a special holiday in the wintertime might be impacted by cascading infections from those that do.
samizdis 6y ago
I posted this article a week ago, but it went almost unnoticed: You Don’t Get Colds from Being Cold https://news.ycombinator.com/item?id=25572907 https://news.ycombinator.com/item?id=25572907
- jerome-jh 6y ago
  Should I summarize the article, cold (low temperature) has no relation with being infected: two groups of people inoculated with a virus, one with wet suits in a cold environment, the other in a normal environment, develop a cold (the disease) at equal rate. Being in cold weather causes the same symptoms as "having a cold": teary eyes, runny nose and chills. The article postulates this is the root of the belief that cold weather causes "common cold".

nicbou 6y ago

I got curious, because I got a cold or something similar after walking in the snow with wet boots for a few kilometres. It's the second time it happens to me. From what I gather, that makes you more vulnerable to viral and bacterial infections. Adding to that, people spend more time in enclosed spaces in the winter, making exposure more likely.

legerdemain 6y ago
It's easily observable that colds are more common in winter (at least in temperate climates where winter is the cold season). I've just always had trouble buying the argument that "people spend more time in enclosed spaces" in winter. At least not a degree significant enough to make a difference. I go to an office and spend the same amount of time in it in the winter and in the summer. Employees at meatpacking plants and Starbucks baristas don't get to work outside in the summertime. Children still go to school, their school days are just as long, and they don't have classes outside even if the weather allows it. You still have to walk the dog, whether it's summer or winter. All the outdoor activities that are easier to do in warmer weather just don't seem to be universal enough to explain effects on a whole population. Most people spend very little time hiking outdoors. As a fraction of the total number of people in the entire country, the number of people who play tennis outdoors is probably tiny. Drinking at the bar versus drinking on an outdoor patio barely seems worth mentioning. Maybe the cold epidemics are driven by agricultural workers who stay indoors in winter? At least they're pretty numerous, there are more of them than there are tennis players...
- maelito 6y ago
  > I go to an office and spend the same amount of time in it in the winter and in the summer. Employees at meatpacking plants and Starbucks baristas don't get to work outside in the summertime. Children still go to school, their school days are just as long, and they don't have classes outside even if the weather allows it. You still have to walk the dog, whether it's summer or winter. This is very different in my case (France). In the summer, windows are often open, which suffice to make a big difference I believe, work and home. Never in winter. In summer, half or our work meals are eaten outside or in well ventilated restaurants. Winter -> at most you walk fast 2 minutes to get in a hot building again. Social activites are all closed rooms in winter.
  - legerdemain 6y ago
    Ah! What a fascinating world. The parts of the US that I am familiar with make extremely widespread use of indoor climate control. Many buildings, such as offices and schools, have windows that barely open or don't open at all. And even if the weather permits you to eat outdoors, there usually isn't enough public space where you could do it comfortably and safely. I guess you could drive to a restaurant and then eat in your car with the windows rolled down.
    - graeme 6y ago
      Notably the US had high summer covid cases in the AC belt, in contrast to the northeast and also in contrast to canada and europe, where hermetically sealed environments are less common. I’d be curious to know what flu and cold season is like in the south. There may also be seasonal changes to hvac systems in milder climates. They all have varying degrees of recirculation vs bringing in outside air. If you are running heavy ac or heavy heating, it costs more to bring in outside air. So there may be seasonal variations in recirculation settings even within the same sealed environment. I’m less confident on this point though as I don’t know hvac’s very well and they are supposed to filter viruses.
- maxerickson 6y ago
  Humidity factors into how long many viruses can remain viable. Covid lasts longer in dryer air. Beach trips, playgrounds, etc probably do add up.
jerome-jh 6y ago
Not that I want to contradict your experience, it is actually very common. But I would truly be interested in knowing the causality relationship between having the feet wet and cold and having a "common cold", that is an infection of the nose/sinuses/throat/lungs.
- lultimouomo 6y ago
  It has been suggested that cold reduces flow in the nasal blood vessels and this hinders immune response, giving the virus a foothold for infecting the organism. I read a study about a bunch of people being left with their feet in a pool of cold water and it showed an increased infection rate vs the control group, but I don't remember how significant and I cannot find it anymore.
- kijin 6y ago
  Your feet have a large blood supply and a large surface area. Getting your feet wet is a very effective way to lower your body temperature.

maelito 6y ago

My bet is that "interior air is renewed less frequently" makes most of the effects. It doesn't look hard to test experimentally.

DownGoat 6y ago

>> But there is still this very common belief that we get ill by getting cold in a physical sense, while e.g. being outside with not warm enough clothes. This is kinda true, the body produce mucus (snot) in the nasal passages. Microbes sticks to this, and when swallowed are neutralized by our stomach acid. But cold air slows down this process, so our first line of defence doesn't work as well during winter. There are also factors such as behaviour changes like spending more time indoors, closed windows and a lot of other stuff that also likely helps spread infections.

kijin 6y ago
I think there are multiple factors, each of which only increases R by a little bit, but when combined produce a noticeable increase. Lack of ventilation is certainly a major factor. The temperature difference between indoors and outdoors is much larger in the winter, so people are more reluctant to let in fresh air. We also don't wash winter clothes as often as we do summer clothes, so viruses that stick to fabric might have more chances to get into our bodies. Homes and public spaces get cleaned less often, too, as they don't feel as sticky and smelly as they do in the summer. Ditto for our own hands, which is probably more important that any of the other factors mentioned here. In the United States, two of the largest mass migration and shopping events of the year take place in the early to mid-winter: Thanksgiving and Christmas. In China, COVID-19 began to spread in earnest outside of Wuhan around Chinese New Year. Even societies that don't have a special holiday in the wintertime might be impacted by cascading infections from those that do.

samizdis 6y ago

I posted this article a week ago, but it went almost unnoticed: You Don’t Get Colds from Being Cold https://news.ycombinator.com/item?id=25572907 https://news.ycombinator.com/item?id=25572907

jerome-jh 6y ago
Should I summarize the article, cold (low temperature) has no relation with being infected: two groups of people inoculated with a virus, one with wet suits in a cold environment, the other in a normal environment, develop a cold (the disease) at equal rate. Being in cold weather causes the same symptoms as "having a cold": teary eyes, runny nose and chills. The article postulates this is the root of the belief that cold weather causes "common cold".