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Researchers Explain Why Flu Comes In the Winter
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."
Just too slow when you've got the flu
Where does Madagascar fit in that theory?
wait, the virus survives best @ 50% humidity and less - but the virus feels at home @ nearly 100% humidity? does not compute
Why it seems to always be an epidemic in the winter is a new discovery, I mean unless you knew it was about the humidity and did not share with the rest of the world.
When you cant win, ad hominem.
Nobody thought of it before? A lot of research comes from a single "wait a minute, why does this happen?" Most people thought it was related to temperature, then most people thought temperature was an old wives' tale but had no idea the reason.
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.
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
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.
Doctors destroy health, lawyers destroy justice, universities destroy knowledge, religion destroys spirituality
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.
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?
The reason it is called air conditioning is not just because it heats and cools your home/work/car is also because it lowers the humidity. This is one of the reasons why you can turn on ice cold air in your car and it will still defrost your windows to an extent. http://en.wikipedia.org/wiki/Air_conditioning An air conditioner (often referred to as AC) is a major or home appliance, system, or mechanism designed to change the air temperature and humidity within an area
When you cant win, ad hominem.
It's been a widely supported theory for some time but perhaps, never proven until now.
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My wife *knows* it is caused by exposure to cold weather :)
So it means you have a heater, not an air conditioner. Most people have air conditioners.
When you cant win, ad hominem.
What is really interesting is how many of these old hand-me-down tidbits from Grandma wind up being rooted in accuracy, even if the underlying logic is flawed. The existence of recorded information has been a boon to modern medical practices, but prior to the very last few generations, how much accurate medical knowledge one had access to was directly proportionate to the quality of the info passed down through the matriarchal network.
Happiness in intelligent people is the rarest thing I know.
Ernest Hemingway
Absolute humidity is how much moisture there is in the air total relative humdity is how much moisture there is in the air compared to the ammount it can hold at that temperature. When you heat your house with a sealed heating system (heating with an open fire is more complex because there is water in the combustion prducts) the absolute humidity stays the same but the relative humidity drops.
And relative humidity not absolute humidity is what we generally care about.
note: i'm known as plugwash most places but i screwd up registering that here somehow in the past and now can't register
No one said that heat alone removes humility, a roaring fire in the fireplace will not remove humidity, but that is not how conditioners work.
When you cant win, ad hominem.
The holidays are mostly in the winter along with people staying indoors because its cold
For a long time it was thought that people getting together passed the virus
Try looking at a psychometric chart sometime. Heating does not change the amount of moisture in the air. Air can hold more moisture at higher temperatures, which is why air feels "dryer" when it is heated coming out of your furnace.
Or you could stick a bucket under your condensate drain off your AC/furnace and see how much water collects in the winter.
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.
"Drive Fast Kill Slow"
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 outdoor air temperature/humidity levels for several days during winter, rather than anything with indoor conditions.
Explain this: I live in Australia (holidays primarily in summer), in a mediterranean (south calif.) climate. Hot dry summers (low humidity) and wet winters (high humidity), with few people having central heating (it ain't cold enough to bother). Yet we still have winter as flu season. Hypothesis dismissed.
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.
That answer your question? I didn't even have to read further than the summary to find that (I'm an Australian too, btw).
That answer your question? I didn't even have to read further than the summary to find that (I'm an Australian too, btw).
No, Perth is certainly not that humid in winter, maybe 60-70%. And less humid in summer.
In winter, people make little to no vitamin D: http://en.wikipedia.org/wiki/Vitamin_D_and_influenza
Even in places near the equator, if people stay indoors to avoid rain, they will have lower vitamin D levels, unless they supplement.
A 21st century issue: the irony of technologies of abundance in the hands of those still thinking in terms of scarcity.
http://www.drfuhrman.com/shop/super_immunity_book.aspx
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 eat a lot of veggies.
In the case of influenza, a lot of it is probably due to vitamin D deficiency in the winter, whether from the Earth's tilt relative to the sun or from cloudy weather and stay indoors in rainy season near the Equator. People probably generally eat less vegetables in winter, too.
A 21st century issue: the irony of technologies of abundance in the hands of those still thinking in terms of scarcity.
I'm not a scientist, and I've conducted no fancy experiments... but based on what I already knew, I just kind of assumed that humidity was a key factor. Considering, you know, it goes straight to shit in the winter, once the furnace starts coming on constantly. I get nosebleeds as the humidity lowers, and again closer to spring sometimes (though around spring it could just be the reintroduction of pollen). It's a pathetic 16% humidity in here right now, which is so damn low it even makes 70 feel relatively chilly. And it could be even lower--I've never even seen it go below 16%, so it's possible that's just the lowest it will read. As far as temperature goes, that doesn't really change much throughout the year... 70-74 when the furnace regulates it, and up to 95 or so in the summer, with the occasional slightly higher temperature.
Of course, it doesn't help the fact that people tend to be inside more often when it's cold out. Well... actually that does help... the viruses. Perfect survival conditions, and lots of people around sneezing to spread them. It's like a flu paradise. Those damn viruses should be thanking us, but all we get is infections.
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.
This is really, really interesting.
I haven't had the flu. Not ever. I've got two dehumidifiers running full time to keep my house at 60% humidity. I pull several gallons of water out of the air every day. With them off (if I forget to empty the tanks before I leave for work) it'll creep up to 90% humidity.
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ECHELON is a government program to find words like bomb, jihad, plutonium, assassinate, and anarchy.
Relative humidity. The ability of air to absorb water goes up with its temperature. So, for a fixed amount of moisture in a quantity of air, when you heat it, its capacity to absorb more goes up.
Have gnu, will travel.
I read something similar a few years ago, but the connection was made between absolute humidity and the survival of influenza. On reading this article, it seems unclear to me what type of humidity is being referred to...absolute or relative. Leave it to the Wall Street Journal to write a crappy scientific article. I suppose relative humidity is usually measured in percentages, but still.
What I found most compelling about the idea of absolute humidity being the important factor was that it explains why influenza is less common in Phoenix, for example. Hot desert areas usually have low relative humidity, but the absolute humidity in grams H2O per cubic metre is usually quite high.
This and no other is the root from which a tyrant springs; when first he appears as a protector - Plato (423 to 327 BC)
"...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?
I wish I had to just worry about keeping the humidity level down. I have a dehumidifier that I use in the summer to keep it around 35-40%. If it didn't get so hot, I'd just let it creep up to 55 or so percent humidity (it seems to stop not too much higher anyway), but 88 at 50% humidity feels like complete shit; no number of fans will really correct that. A humidifier would be useful for whenever the furnace is on, but I have to question how well they will work... they mostly have tiny "tanks" that look like they wouldn't even hold enough water to make a pot of tea, and I'd be surprised if they could humidify even one closed room for a full 24 hours. And then most of them are the trash type that don't even use pure heat to properly evaporate the water (like a stove), so they would most likely end up putting a mineral deposit layer on everything near it.
I've been trying to figure out a way around this for a while now.
>even if the underlying logic is flawed
Because it's not logic that underlies it, but something more fundamental - experience.
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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.
This is really, really interesting.
I haven't had the flu. Not ever. I've got two dehumidifiers running full time to keep my house at 60% humidity. I pull several gallons of water out of the air every day. With them off (if I forget to empty the tanks before I leave for work) it'll creep up to 90% humidity.
Same here on the dehumidifiers. Guess it's about what part of the world you live in.
Seriously, haven't you experienced the last few weeks of 80-90% humidity with record temperatures here? Also, winter humidity on most days does hover around 60-70% yes, but that's an AVERAGE day. We still experience plenty of days during winter at around 90-100%.
I've wondered why people get sick in the winter and assumed it was due to the dry air...seemed pretty obvious finding proof is the part that made news.
And it could be even lower--I've never even seen it go below 16%, so it's possible that's just the lowest it will read.
VERY very possible... I have 3 in the house. One bottoms out at 16, the other two switch to ---% when it is below 15. Oh, and the one in this room is reading 16 right now... yay.
No, but the steady flow of water coming from the condenser on my furnace is a pretty good clue that it is removing water.
"I'm too busy to research this and form an educated opinion, but I do have time to tell everyone my uninformed opinion."
Right. And I'll venture a guess that its a high efficiency gas furnace. Those attain their high efficiency by removing so much heat from the combustion gas that the water produced by combustion condenses out. There's also quite a bit of energy released by that condensation itself (latent heat of vaporization). So that water isn't extracted from the conditioned (room) air. It's from the combustion gas.
Different story for air conditioners, of course.
Have gnu, will travel.
Here is Arduino based project to control humidity in apartment.
Not really I could have drainage witch
Is a "drainage witch" anything like a Ditch Witch?
Well put. Of course,which experiences are causation and which are correlation are still in the eye of the observing matriarch. I hope mine is logical.
Happiness in intelligent people is the rarest thing I know.
Ernest Hemingway
Also about your heating source. Burning natural gas or using steam radiators puts a lot more water in the air than burning oil does.
I don't know about that... I have a natural gas heater and, as I said, the humidity plummets when it runs a lot.
Also about your heating source. Burning natural gas or using steam radiators puts a lot more water in the air than burning oil does.
The past few years I have only had the heat on one or two nights a year. It really doesn't get very cold for extended periods here. I end up having to set the AC fan to "on" instead of "auto" just to circulate the air in the house.
Hardly common, I had it custom made.
rewriting history since 2109
Those damn viruses should be thanking us, but all we get is infections.
But that is how they thank us! "Hello, thank you for giving me a great environment in which to thrive, as a gift, I offer you some D/RNA.
Hmmm... actually, you have a point... and that DNA/RNA likely gets passed onto any offspring. The only problem is, viruses mutate and evolve, which causes older immune resistance to be virtually useless against newer strains of the virus... so in that case, the little bastards are just bloating our offspring's DNA for no reason!
And since correlation is not causation, it still has not been proven. Other correlations include, the amount of time spend indoors around other people, Levels of vitamin D (reduced sunlight, less D), reduced overall physical fitness due to less physical activity, and changes in sleep behavior due to reduced daylight hours.
Sure. It would just plummet even more if it were an oil heater.
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 similar or the same since hogs are the source of many influenza virus mutations crossing over to humans), how does this result explain this?
Both of these time frames have something else in common though.
People are out in the open less, and in closed areas more, to avoid the weather - touching more of the same things more often, and breathing more recirculated air with micro water droplets form coughs and sneezes.
There are a lot of factors for the flu, it's not a one-cause-fits-all thing.
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