# Why is there more flu in the winter than in summer? **URL:** \ **Category:** Factual Questions\ **Created:** [October 28, 2009, 10:42am UTC](https://boards.straightdope.com/t/why-is-there-more-flu-in-the-winter-than-in-summer/515419 "2009-10-28T10:42:04Z")\ **Posts on this page:** 15\ **Page:** 1
**Author:** ![Kalhoun](https://avatars.discourse-cdn.com/v4/letter/k/3bc359/32.png) [@Kalhoun](https://boards.straightdope.com/u/Kalhoun)\ **Post date:** [October 28, 2009, 10:42am UTC](https://boards.straightdope.com/t/why-is-there-more-flu-in-the-winter-than-in-summer/515419/1 "2009-10-28T10:42:04Z")
That pretty much says it all. Anyone? ---
**Author:** ![Floater](https://avatars.discourse-cdn.com/v4/letter/f/dc4da7/32.png) [@Floater](https://boards.straightdope.com/u/Floater)\ **Post date:** [October 28, 2009, 10:57am UTC](https://boards.straightdope.com/t/why-is-there-more-flu-in-the-winter-than-in-summer/515419/2 "2009-10-28T10:57:40Z")
Just a guess. One reason would be that people tend to keep indoors in closer contact with each other during Winter and thereby get more exposed. ---
**Author:** ![Kalhoun](https://avatars.discourse-cdn.com/v4/letter/k/3bc359/32.png) [@Kalhoun](https://boards.straightdope.com/u/Kalhoun)\ **Post date:** [October 28, 2009, 11:23am UTC](https://boards.straightdope.com/t/why-is-there-more-flu-in-the-winter-than-in-summer/515419/3 "2009-10-28T11:23:14Z")
That’s what I thought too, however, if you don’t go out as much, isn’t there less opportunity to pick up a bug to begin with? ---
**Author:** ![Philster](https://avatars.discourse-cdn.com/v4/letter/p/13edae/32.png) [@Philster](https://boards.straightdope.com/u/Philster)\ **Post date:** [October 28, 2009, 11:51am UTC](https://boards.straightdope.com/t/why-is-there-more-flu-in-the-winter-than-in-summer/515419/4 "2009-10-28T11:51:31Z")
It’s an open debate. But… from New Scientist: There is no one reason why we get more colds and flu in winter. The rhinovirus, which is responsible for up to 40 per cent of colds, cuitures better at a temperature of 32 °C rather than the normal body temperature of 37 °C. However, 32 °C is the normal temperature of the lining of the nose, which is good news for the virus. We do tend to be indoors more often in poorly ventilated areas during the winter and this aids the airborne transmission of viruses. Similarly, ultraviolet will kill viruses and this may be another factor. \* And this \*\*must read \*_from Science Daily:_ > **[Why The Flu Virus Is More Infectious In Cold Winter Temperatures](https://www.sciencedaily.com/releases/2008/03/080330203401.htm)** > > A new finding may account for why the flu virus is more infectious in cold winter temperatures than during the warmer months. At winter temperatures, the virus's outer covering, or envelope, hardens to a rubbery gel that could shield the virus as it... Good info in that link above. ---
**Author:** ![Kalhoun](https://avatars.discourse-cdn.com/v4/letter/k/3bc359/32.png) [@Kalhoun](https://boards.straightdope.com/u/Kalhoun)\ **Post date:** [October 28, 2009, 12:03pm UTC](https://boards.straightdope.com/t/why-is-there-more-flu-in-the-winter-than-in-summer/515419/5 "2009-10-28T12:03:46Z")
Excellent link! Thanks, Philster! ---
**Author:** ![ivan\_astikov](https://avatars.discourse-cdn.com/v4/letter/i/58f4c7/32.png) [@ivan\_astikov](https://boards.straightdope.com/u/ivan_astikov)\ **Post date:** [October 28, 2009, 12:08pm UTC](https://boards.straightdope.com/t/why-is-there-more-flu-in-the-winter-than-in-summer/515419/6 "2009-10-28T12:08:27Z")
> [@Philster](#): > > It’s an open debate. > > But… from New Scientist: > > There is no one reason why we get more colds and flu in winter. The rhinovirus, which is responsible for up to 40 per cent of colds, cuitures better at a temperature of 32 °C rather than the normal body temperature of 37 °C. However, 32 °C is the normal temperature of the lining of the nose, which is good news for the virus. So, is the challenge how to make the nasal cavity a more hostile environment for these little blighters, or can they survive just as well if inhaled down your throat? ---
**Author:** ![Philster](https://avatars.discourse-cdn.com/v4/letter/p/13edae/32.png) [@Philster](https://boards.straightdope.com/u/Philster)\ **Post date:** [October 28, 2009, 2:00pm UTC](https://boards.straightdope.com/t/why-is-there-more-flu-in-the-winter-than-in-summer/515419/7 "2009-10-28T14:00:02Z")
Did you miss all the hype about saline nasal solutions? That makes it ‘hostile’ for germs. ---
**Author:** ![HorseloverFat](https://avatars.discourse-cdn.com/v4/letter/h/8e8cbc/32.png) [@HorseloverFat](https://boards.straightdope.com/u/HorseloverFat)\ **Post date:** [October 28, 2009, 2:32pm UTC](https://boards.straightdope.com/t/why-is-there-more-flu-in-the-winter-than-in-summer/515419/8 "2009-10-28T14:32:13Z")
Aside from being more indoors, cold air dries our nasal passages. This makes them more vulnerable to viruses. It is also been hypothesized that vitamin D deficiency in the winter from lack of sun affects the immune system. ---
**Author:** ![ivan\_astikov](https://avatars.discourse-cdn.com/v4/letter/i/58f4c7/32.png) [@ivan\_astikov](https://boards.straightdope.com/u/ivan_astikov)\ **Post date:** [October 29, 2009, 10:22am UTC](https://boards.straightdope.com/t/why-is-there-more-flu-in-the-winter-than-in-summer/515419/9 "2009-10-29T10:22:18Z")
> [@Philster](#): > > Did you miss all the hype about saline nasal solutions? That makes it ‘hostile’ for germs. Can I snort cocaine instead? ---
**Author:** ![JillGat](https://avatars.discourse-cdn.com/v4/letter/j/9fc29f/32.png) [@JillGat](https://boards.straightdope.com/u/JillGat)\ **Post date:** [October 29, 2009, 5:08pm UTC](https://boards.straightdope.com/t/why-is-there-more-flu-in-the-winter-than-in-summer/515419/10 "2009-10-29T17:08:08Z")
But flu also circulates in tropical parts of the world, where it doesn’t get cold in the winter. How to explain that? And H1N1 spread just fine in warmer weather. ---
**Author:** ![HorseloverFat](https://avatars.discourse-cdn.com/v4/letter/h/8e8cbc/32.png) [@HorseloverFat](https://boards.straightdope.com/u/HorseloverFat)\ **Post date:** [October 29, 2009, 5:23pm UTC](https://boards.straightdope.com/t/why-is-there-more-flu-in-the-winter-than-in-summer/515419/11 "2009-10-29T17:23:20Z")
It simply spreads faster in the cold. ---
**Author:** ![Philster](https://avatars.discourse-cdn.com/v4/letter/p/13edae/32.png) [@Philster](https://boards.straightdope.com/u/Philster)\ **Post date:** [October 29, 2009, 5:30pm UTC](https://boards.straightdope.com/t/why-is-there-more-flu-in-the-winter-than-in-summer/515419/12 "2009-10-29T17:30:05Z")
> [@JillGat](#): > > But flu also circulates in tropical parts of the world, where it doesn’t get cold in the winter. How to explain that? > > And H1N1 spread just fine in warmer weather. It spreads off season and in warm climates, because in its weakened state it’s not powerless. H1N1 is spreading well enough in the warm that it is scaring the bajeebers out of people about how lethal it might be during the actual flu season. Hence the threads on it as flu season approaches. ---
**Author:** ![Mama\_Zappa](https://avatars.discourse-cdn.com/v4/letter/m/71e660/32.png) [@Mama\_Zappa](https://boards.straightdope.com/u/Mama_Zappa)\ **Post date:** [October 30, 2009, 12:18am UTC](https://boards.straightdope.com/t/why-is-there-more-flu-in-the-winter-than-in-summer/515419/13 "2009-10-30T00:18:01Z")
> [@HorseloverFat](#): > > It simply spreads faster in the cold. I think the deal is, most flu viruses survive better because of a sort of “coat” that forms in colder weather: > **[What Is the Flu?](https://www.webmd.com/cold-and-flu/what-is-flu)** > > Learn more from WebMD about the flu, including causes, symptoms, types, risk factors, treatment, and prevention. [http://www.injuryboard.com/national-news/flu-virus-needs-winter-coat-to-survive.aspx?googleid=29918](http://www.injuryboard.com/national-news/flu-virus-needs-winter-coat-to-survive.aspx?googleid=29918) For some reason, H1N1 survives to spread despite that coating, hence its prevalence even before colder weather. ---
**Author:** ![bump](https://avatars.discourse-cdn.com/v4/letter/b/7c8e57/32.png) [@bump](https://boards.straightdope.com/u/bump)\ **Post date:** [October 30, 2009, 3:58am UTC](https://boards.straightdope.com/t/why-is-there-more-flu-in-the-winter-than-in-summer/515419/14 "2009-10-30T03:58:49Z")
> [@Philster](#): > > Did you miss all the hype about saline nasal solutions? That makes it ‘hostile’ for germs. Maybe that’s why boogers are salty… ---
**Author:** ![Philster](https://avatars.discourse-cdn.com/v4/letter/p/13edae/32.png) [@Philster](https://boards.straightdope.com/u/Philster)\ **Post date:** [October 30, 2009, 1:03pm UTC](https://boards.straightdope.com/t/why-is-there-more-flu-in-the-winter-than-in-summer/515419/15 "2009-10-30T13:03:43Z")
You would know.