9

Most people have heard the phrase "summer cold." Is there any truth to the concept that people are more prone to the common cold during summer months? More generally, is there any particular (preferably specific) time of year that people are more susceptible, outside of "winter" (given the discussion on Does being cold increase your chances of catching the common cold?)?

As far as the summer cold is concerned, it seems there's some thought that people's allergy symptoms are incorrectly attributed to a cold (MedicineNet, a CNN article from last year), but it seems likely that those conditions would also be present in the spring.

10

Severe cases of common cold cause set of symptoms know as "influenza-like illness".

CDC definition of "influenza-like illness" case is:

fever ≥ 100°F AND cough and/or sore throat

There is no doubt, that "flu-like" is seasonal, with peak just past mid-winter. This can be clearly seen from effect of collaboration between CDC and Google, Google Flu Trends.

FluTrends US

Scientific basis on these studies are described in this Google Research paper, which has been originally published in Nature.

  • I misread the first part of the Nature letter as being the whole thing, and posted a misguided comment (now deleted). @Vartec has now clarified, and now I encourage you to vote for this answer over mine. – Oddthinking Jun 30 '11 at 14:41
  • @Odd: yeah, one probably needs subscription to view the whole thing there, that's why I've included link to the paper hosted on Google site. Btw. thanks for the recommendation, anyway there is no reason why one cannot upvote both answers ;-) – vartec Jun 30 '11 at 14:47
  • Interesting use of google trends! – Alain Jun 30 '11 at 16:54
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(I'm going to do a subtle bait-and-switch in my answer, so I can match the evidence I found! Watch for it, and vote accordingly.)

People use the term "cold" and "flu" rather loosely. The generic term of Influenza-like Illness covers both influenza, common colds (caused by a number of different viruses) and other causes. I assume "summer cold" applies to all of these.

Influenza itself, is seasonal:

In the Northern hemisphere, winter is the time for flu. The timing and duration of flu seasons vary. While flu outbreaks can happen as early as October, most of the time influenza activity peaks in January or later. The figure below shows peak influenza activity for the United States by month for the 1976–77 through 2008–09 influenza seasons. The month with the highest percentage of cases (nearly 50%) was February, followed by January with 20% and March and December, with approximately 15% of all cases.

Peak Month of Influenza Activity

Peak Month of Influenza Activity 1976—77 through 2008—09 Seasons

The source for this is the US Center for Disease Control. They are an authoritative source for disease information, but their information is poorly cited on their web-site.

(The bait-and-switch was that the OP asked about common colds, I generalised to Influenza-like Illness, and then gave evidence about Influenza alone. I should only get away with this if you agree that Influenza fits as one of the key diseases referred to under 'Summer Cold'.)

  • Given the other evidence as to the common trends of the flu (@vartec's answer specifically), it seems likely that the flu may not be "one of the key diseases." – Ian Pugsley Jun 30 '11 at 13:07
  • @Ian, I don't know how you reach that conclusion. Please explain. (Not that I am attacking @vartec's answer. I think he avoids my bait-and-switch, and deserves credit.) – Oddthinking Jun 30 '11 at 13:20
  • +1 for having such good resources and graphs, -0.5 for generalizing, +0.5 for being upfront about it! – Alain Jun 30 '11 at 16:53
  • @Alain :-) So if I hadn't been upfront, you would have awarded me 0.5 votes, which, when rounded up... – Oddthinking Jun 30 '11 at 17:01
  • @Oddthinking - in retrospect, you are correct, @vartec's answer doesn't necessarily imply that. I would like to see some support of the flu as one of the key diseases, though. – Ian Pugsley Jul 1 '11 at 14:11
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What is called a "cold" isn't even well defined and can be caused by many viruses. However there are several indications that infection is much more common in the winter. Explanations for this range from the drier air found in heated homes, to the increased density inside, and the US school calendar.

However the wide range speculation by multiple reputable sources indicates that this is something we are far from understanding with any certainty.

Spam prevention restricts the number of sources I can post.

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