I am looking for information on the state of knowledge on the relative
importance of various mechanisms for cold and/or flu transmission from
person to person. I'm sure scientific studies have been performed over
the decades that provide information on questions such as: Is touching
virus-contaminanted surfaces (doorknobs or what have you) a more or
less common route of transmission than breathing airborne particles
(e.g. after someone has sneezed?). The answers provided should be
based on scientific studies and thus contain some references to such
studies.

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Request for Question Clarification by pafalafa-ga on 01 Jan 2005 05:11 PST

Hello cosmomike, and a happy (and cold-free) new year to you!


A comprehensive review of the epidemiology of colds was published two
years ago, summarizing all the major studies on the topic.  It came to
the following conclusion:

"In summary, whereas some experts agree that indirect contact with
contaminated secretions appears to be the most efficient means of
transmission, others find that large-droplet transmission of such
secretions is more important."


Bottom line...no one knows for sure, but both aerosols (droplet
transmission) and hand contact (indirect contact) both seem to be
significant routes to infection.  And as noted in the comments from
cone10-ga, below, it does appear to differ somewhat depending on the
virus itself.

The study includes a review of the fairly well-known card-playing
experiment that you metioned (some of the card players wore large
collars to prevent them from putting their hands to their faces --
must have been quite a sight!).

I cannot post the full review study here, since it is protected by
copyright.  But I can certainly summarize its main points, and provide
you a full citation so you could obtain a copy from the library.

But if you're looking for a conclusive report that states one route is
more important than another, I don't believe you'll find it.

Let me know how you'd like to proceed.

pafalafa-ga

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Clarification of Question by cosmomike-ga on 06 Jan 2005 20:50 PST

Pafalafa, 

If you want to summarize the main points and post the reference, I'd
consider that a fine answer.

cosmomike

The CDC says that "occasionally" you can get the flu from, say,
touching a door knob (http://www.cdc.gov/flu/keyfacts.htm).
Howstuffworks says that it is transmitted through the air
(http://health.howstuffworks.com/flu2.htm). Essentially, though, it's
all a matter of how much contact the virus has with entrances to your
body (a cut, the mouth, the eyes, the nose). It's easier to contract
it through the air because one doesn't usually, if you will, wash your
nose (like you would wash your hands).

Hope that helps,
Dave

Thanks for yourt comment dave14. I am looking for scientific
information to support and better quantify the relative importance of
the different routes of transmission. You say "It's easier to contract
it through the air." I have heard the opposite (touch is the more
common route). But that's just the problem: I "have heard" touch is
more common; can anyone identify studies that offer hard evidence
either way?
Thanks again for taking the time to comment.

I asked this a few days ago.


http://answers.google.com/answers/threadview?id=440530

I'm no expert, but I've just finished up with a course in
microbiology...  Route of transmission depends alot on the organism. 
In the case of the common cold, there are a number of viruses
responsible, and frequently a cold is a mixed infection of several
viruses.  Half of all colds are caused by rhinoviruses--other
offenders include paramyxoviruses, corona viruses, adenoviruses,
enteroviruses, and reoviruses.  Each of these have varying degrees of
hardiness in the "outside" environment, and their "preferred" target
tissues.  (BTW--the reason no vaccine exists for the common cold is
this daunting array of bugs--there are 110 serological types of the
rhinovirus alone, and there is no practical way to create a vaccine
that could cover this horde...)  What I learned was that these viruses
"like" to enter the body thru the delicate mucosa of the eye, and are
less invasive thru the tissues of the upper respiratory tract--hence,
colds are less likely to be passed via inhaled aerosols, and are more
likely to be passed from rubbing eyes with contaminated
hands--however, the viruses are not particularly long-lived in the
outside world, so you need to have freshly contaminated hands from
infected mucus--a pre-schooler works very well as a vector in my
experience.
On the other hand, so to speak, the flu is caused by strains of
orthomyxovirus, and its preferred route is indeed inhaled
aerosols--its "portal of entry"/target tissues are the ciliated
epithelial cells of the upper respiratory tract...
For hard data, I'd suggest googling these viruses--I'm sure you'll run
into "hard data" for your needs...

Just4fun2: Thanks for posting a comment. Your question is similar, but
does not get into measuring the relative frequency of catching colds
via hands vs. airborne particles--that is what I am after.

I heard about a study where they had well people play cards with
people with colds, and also had well people just be in close proximity
to people with colds, without playing cards. The frequency of colds
caught would then be compared between each situation... That would be
an example of the kind of study I am after.

Cone10: Thanks for the informative comment. Intersting to hear
differences between cold and flu visrus transmission. I did not know
there were so many cold/flu agents out there--may make finding a
consistent answer to my question more difficult (e.g. "depends on the
particular virus mix in each case")