
Why Is Flu Common in Winter? - pwg
http://online.wsj.com/article/SB10001424127887324235104578241632319689490.html
======
gojomo
Some believe lower natural production of immune-system-important Vitamin D
(through less sun exposure) is a factor, though studies have been mixed:

<http://en.wikipedia.org/wiki/Vitamin_D_and_influenza>

(I'd guess higher levels of sunlight might also help sterilize viruses on
surfaces and suspended in the air, but have no handy references supporting
that theory.)

There's also the unlikely-but-fun fringe theory that fresh flu viruses
regularly fall to Earth from space:

<http://www.panspermia.org/panfluenza.htm>

Perhaps either a certain part of Earth's orbit, or colder hemispheric
temperatures, mean more falling space flu? :)

------
viscanti
"Consider wearing a good-fitting mask, with no gaps around the nose or mouth,
in public."

This can probably be abstracted. Any activity that makes people not want to
hang out with you or be near you will reduce your odds of getting the flu.

~~~
orofino
Worth noting that the porous, "paper", type masks that you sometimes see
people wearing (being in Tokyo right now I'm understating their prevalence),
are entirely worthless for defending against viruses. They're too small for
those masks to be effective.

They're good for blocking particulate matter though, so if you're trying to
prevent blood spatter to the mouth, thumbs up.

~~~
bwooce
The irony is that they're excellent for preventing aerosol droplets filled
with virus from the wearer. Wearing one when infected is therefore
responsible.

~~~
greggman
no, staying home and not getting your co-workers sick by bringing your sick to
the office is responsible. Coming to work sick, even with a mask, is
irresponsible.

------
asher_
This isn't a question that already doesn't have an answer. Researchers showed
at the Common Cold Centre in London that body temperature has an impact on the
likelihood of catching flu. The reasoning is that during the cold, less blood
flows to the extremities to maintain core body temperature. This includes less
blood flow to the nose.

Flu lives in the nose, and white blood cells are what attacks flu, so having
less blood in the nose means less white blood cells which means less chance of
killing the virus off before it takes hold.

~~~
pretoriusB
> _This isn't a question that already doesn't have an answer. Researchers
> showed at the Common Cold Centre in London that body temperature has an
> impact on the likelihood of catching flu._

That research was far from conclusive or scientific.

------
mynameishere
I always thought it was a simple matter of contagion being partly a function
of proximity between people. Since proximity is more common in bad weather,
with people staying indoors, the flu spreads more easily in winter.

------
dchichkov
Isn't it just that viruses survive longer at lower temperatures? As per
wikipedia:

"Flu viruses can remain infectious for about one week at human body
temperature, over 30 days at 0 °C (32 °F), and indefinitely at very low
temperatures (such as lakes in northeast Siberia)."

~~~
BenoitEssiambre
That has always been my hypothesis. When you cough in the winter, germs are
cooled and conserved on the ground. Then when someone brings in water or snow
from their shoes, they are basically bringing in refrigerated puddles of
germs.

Someone must have tried to verify this?

------
crazygringo
So what I've never been able to understand is how it works in areas which
don't have cold winters.

For example, when I lived in Brazil (Rio de Janeiro), where the temperature
never really goes below 65 F, I was surprised that everyone would tell me that
people get colds/the flu not in the winter, but in the _summer_ \-- supposedly
because the constant shifts between hot summer air and cold A/C indoor air
made you more susceptible.

But it seems to be common "scientific" knowledge that flu is a wintertime
thing. Is that not always the case, though? Are there places where it actually
is a summertime thing? Or in places without much change in the seasons, is
there no yearly variation?

~~~
aasarava
From TFA: "It's also fine in humidities above 98%, which you find in the rainy
season in the tropics," she says, where the conditions outside resemble the
environment the virus finds in the body.

------
chipsy
<http://en.wikipedia.org/wiki/Vitamin_D_and_influenza>

------
ChrisNorstrom
I wonder if the drought and dryness is causing the Flu Epidemic in the USA
this year.

A lot of time and money is lost in dealing with the flu each year. So if the
owners of big buildings, public spaces, & mass transit installed humidifiers
to combat the flu, I wonder how much of a difference would it make...

~~~
spydum
Something that has never quite made sense to me is, the flu virus is
apparently very delicate.. drying out very quickly. However, it seems to
thrive more in cold, dry conditions. How can this be? And to your point, would
humidifiers help or hurt?

~~~
alwaysinshade
> would humidifiers help or hurt?

I'd imagine in humid conditions the pathogens bind with the fine water
droplets in the air to form an aerosol, which (I assume) sticks to surfaces
more readily whereas in dry conditions the contaminants would remain airborne
far longer and stick to the mucosa once inhaled.

------
eurleif
I wonder if in the future, government regulation will require central heating
systems to come with built-in humidifiers. Seems like a heater without a
humidifier has serious negative externalities.

------
xutopia
That's awesome! Now if I could find a humidifier that is silent and that I
don't have to fill every day.

~~~
Tichy
and that is not a breeding ground for germs...

~~~
stock_toaster
or for mold.

~~~
ars
Put salt in the water, it will inhibit many microorganisms, and if some salt
gets in the air it won't hurt you - and may even help see:
<http://en.wikipedia.org/wiki/Salt_therapy>

(But only once, since the salt will stay behind as the water evaporates.
Unless you change the water, in which case add some more.)

