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Medicine Science

Researchers Explain Why Flu Comes In the Winter 129

Posted by samzenpus from the cold-in-the-cold dept.
First time accepted submitter ggrocca writes "Using human mucus as a testbed for how well influenza virus thrives in different humidity conditions, researchers at Virginia Tech found that the virus survived best if humidity is below 50%, a typical indoor situation during the winter in temperate climates due to artificial heating. The virus begins to find itself at home again only when humidity reaches almost 100%. Unsurprisingly, the latter finding explains flu spikes during rainy season in tropical climates. Full paper on PLOS ONE."
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Researchers Explain Why Flu Comes In the Winter More

Researchers Explain Why Flu Comes In the Winter

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  • First sneeze

  • Where does Madagascar fit in that theory?

    • Re: (Score:2)

      by thaylin ( 555395 )
      The virus begins to find itself at home again only when humidity reaches almost 100%. Unsurprisingly, the latter finding explains flu spikes during rainy season in tropical climates.
    • Yeah, packing that many kids in a theater IS asking for trouble.

    • Re: (Score:1)

      by Anonymous Coward

      Madagascar is fairly irrelevant to this. I mean, the virus would have to reach it first before survivability comes into question, which it can't because the port is always closed.

  • wait, the virus survives best @ 50% humidity and less - but the virus feels at home @ nearly 100% humidity? does not compute

  • Something else to keep in mind (Score:3)

    by Guppy06 ( 410832 ) on Sunday January 20, 2013 @09:52AM (#42638939)

    Just because central heating drives down the relative humidity to 50% indoors doesn't mean it's not also near 100% outdoors, where colder temperatures give much higher relative humidity for the same humidity ratio.

    • Re: (Score:3)

      by thaylin ( 555395 )
      What is the point? So, it does not survive as well outside, except in our systems, but it will still thrive in your home.

      • Re: (Score:1)

        by Anonymous Coward

        No, it survives well outside and thrives in your home.

    • Re: (Score:2)

      by pz ( 113803 )

      When it is cold outside, mucus membranes (in the nose, most importantly for this discussion) go into overdrive. We get sniffly noses, whether we have an active nasal infection or not, and sniffle more often than in the summer. Much more often.

      So, if someone who has a sniffly nose happens to wipe said nose with their hand and then immediately touches something else, say a doorknob, or a light switch, or a keyboard, or the cup of coffee the barrista just handed you, or a hand in a handshake, then, there's a

  • Old news (Score:1)

    by Anonymous Coward

    Feb 2009 article found the same thing:
    http://articles.cnn.com/2009-02-11/health/healthmag.humidifier.flu_1_humidity-water-vapor-winter-flu-season?_s=PM:HEALTH

  • How do they explain dry areas? (Score:3)

    by __aaltlg1547 ( 2541114 ) on Sunday January 20, 2013 @09:55AM (#42638955)
    In Phoenix, relative humidity is below 50% on average from April thru September. In Albuquerque, it's March through June. Does flu hold out year round in those areas?

  • The virus is around year round. However, in the winter you stay inside and get less sunlight...thus less vitamin D.

      • Re: (Score:2)

        by MobyDisk ( 75490 )

        If this is true, then why not have everyone take Vitamin D supplements during the winter, instead of giving them flu shots?

    • Re: (Score:2, Insightful)

      by PRMan ( 959735 )

      Not to mention that your immune system is compromised trying to keep you warm in cold weather. But why let that common, eternal wisdom get in the way of a new study?

      And isn't it dry in cold places like Colorado in the winter? When I was there, it was so dry I got nosebleeds just because of the dryness. And yet people were still getting colds by the dozens.

      • Re: (Score:3)

        by thaylin ( 555395 )
        First there is no empirical link between the temperature dropping and the weakening your immune system, that could be, and possibly is, an old wives tale. A previous study showed that the people must likely to get sick during the winter are those with already weakened immune systems. Also the study said it thrives at the following x50 and x is approximately 100, therefore 0-49% humidity falls within those parameters.

      • Re: (Score:1)

        by TheLink ( 130905 )
        maybe there's a higher amount of virus in blood laden snot.

      • > And yet people were still getting colds by the dozens

        I've been a vegetarian off and on over my life. Right now, I have just been trying to eat better, exercise a little more, and I consider myself to be a flextarian (I eat meat, just way less of it than typical Americans).

        During times of eating right, I get sick a fraction of what my friends and family do, but if I eat the Standard American Diet, I get sick every time someone sneezes around me.

        Right now, almost every single co-worker I have at work has

        • http://www.drfuhrman.com/shop/super_immunity_book.aspx [drfuhrman.com]

          Things to be aware of that he would mention:
          * vitamin D deficiency
          * iodine deficiency
          * B-complex deficiency
          * omega-3s deficiency
          * eat a lot of vegetables, fruits, and beans, and some nuts, seeds, and whole grains
          * avoid refined sugars and grains
          * avoid food additives (artificial colors, artificial flavors, most preservatives)

          Many vegans and vegetarians eat a refined starch-heavy diet with too little vegetables and so are sicker than meat-eaters who also

  • How does school and holiday travel figure in? (Score:3)

    by __aaltlg1547 ( 2541114 ) on Sunday January 20, 2013 @09:59AM (#42638973)

    I always figured schools were a big part of it. Pack 25-35 kids in a classroom. Reshuffle the kids 6 to 8 times per day. It's an ideal environment for spreading any contagious disease.

    So are airplanes.

    • Re: (Score:2)

      by mjwx ( 966435 )

      So are airplanes.

      Aeroplanes are actually cleaner than most office buildings due to the fact they have better quality HEPA filters.

      The reason most people feel sick from air travel is the extremely low relative humidity on-board (6%) which leads most people to get dehydrated because they dont drink enough water. Add alcohol into the mix and you have people becoming extremely dehydrated. If I dont drink enough water on a flight over 4 hours, I'll usually get off with hangover like symptoms (dizziness, headache, slight nause

  • the fact that when it's cold outside, more people are inside, especially communal indoor places like malls, food halls, etc. A more efficient route of transfer?

  • My wife *knows* it is caused by exposure to cold weather :)

  • I work outside year round with a week or two off when its really cold. (below 20 F). I hardly ever get sick. Yes I'll get head colds runny nose and maybe a light cough but who doesn't when the weather is changing. but as far a s the flu. almost never. I can only think of twice in the last 17 years and the firs time I still worked.

    • Re: (Score:2)

      by thaylin ( 555395 )
      If you are doing manual labor then you till probably have a very strong immune system
      • I did a lot of playing in the dirt when i was a kid and I guess I do now too. I think that is part of the problem now days is people are trying to keep their kids out of the dirt so they never build tolerances and end up being sicker more often when older.

    • I work outside year round with a week or two off when its really cold. (below 20 F). I hardly ever get sick. Yes I'll get head colds runny nose and maybe a light cough but who doesn't when the weather is changing. but as far a s the flu. almost never. I can only think of twice in the last 17 years and the firs time I still worked.

      Because for the flu to spread or even the common cold, you have to come into contact with an infected person. Most likely, there are fewer people you come into contact with in the course of your work than say in an office building and therefore the likelihood of you coming into contact with an infected person is even less.

      It is the same reason why the monks in the middle ages survived the plague that decimated the towns. Since they were isolated from the infected people (or fleas), they did not contract it.

      • That should have been "If you study epidemics..." not pandamecis, which is not only mispelled, but by the time a pandemic occurs, it hits both city and country alike.

  • Typical indoor HVAC design conditions: Summer - 75F / 50% RH, Winter - 70F / 30% RH. So indoors I would think the virus would survive well year round, just better during winter.

    Outdoors the air temperature might swing 20-30F between the day and night. This is going to swing the RH levels in an even wider range - maybe between 20% and 80% depending on season, time of day, local climate etc.

    I would think the virus survival would correlate better with time periods when there isn't much change in the outdo

  • Flaw in the study (Score:3)

    by Dcnjoe60 ( 682885 ) on Sunday January 20, 2013 @11:45AM (#42639799)

    There is a major flaw in the study. First it states that the flu virus thrives in humidity conditions below 50% which explains why in the winter we have these outbreaks. However, with modern heating and cooling systems, indoor humidity levels are almost always below 50%. At 55% is where mold begins to grow, so unless your home or office is damp enough to grow mold, chances are that year round you are at 50% or less humidity, not just during the winter.

    The other flaw is that the researchers point out that the humidity needs to be low as in a room with "...really heated air..." so that the mucos droplets evaporates leaving the virus to float freely. That is not going to be your typical living space, because if it is hot enough to be evaporating mucus droplets in the air then it is either really hot (85 deg F or greater) or really dry, less than 25% humidity, which would mean that most people would be having nosebleeds and other problems.

    So, while the research may be accurate on the zones that the virus does best in, it does not actually translate into the environments we live in and explain the outbreaks we see.

  • "...the winter in temperate climates due to artificial heating."

    Is anyone else missing the lower humidity we generally have in the winter -outside- in temperate climates due to it, you know, being cold?

  • Said to me, today actually, cuz she have a "common flu" at this moment, is that usually she gets it in "cool season". Which means from December till February/March.

    Raining season or hot season, no problems. But cool season*... problems.

    *= Cool .. 33 at day 22-25 at night, low humidity.

  • What about places such as Wyoming and Colorado that are dry (under 50%) for most of the year?

    Also, my family had a hog farm growing up. The hogs were outside exposed to the elements. Every November in the early '80s we got hit with a major influenza outbreak in the hogs approaching 100% among the hogs weighing 60 to 180 lbs. There was no major change in the humidity, and didn't depend on rain or other weather events. Assuming the infection mechanism is similar (and certainly the influenza viruses were simil

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