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Q: Questions about influenza. ( Answered 5 out of 5 stars,   1 Comment )
Subject: Questions about influenza.
Category: Health > Conditions and Diseases
Asked by: thelark2020-ga
List Price: $20.00
Posted: 10 Apr 2006 00:07 PDT
Expires: 10 May 2006 00:07 PDT
Question ID: 717330
Let?s say someone catches influenza on Monday.  
1. During what days will they be the most contagious?

And lets say, while they are contagious, they deposit the flu virus on
a door knob.
2. How long will that virus live on the door knob?

3. The idea that a virus has a season doesn?t make much sense to me. 
If the flu has a ?season? where does it go the rest of the year?

The questions refer to influenza in general, and not specifically
Avian influenza (H5N1).
Subject: Re: Questions about influenza.
Answered By: alanna-ga on 10 Apr 2006 18:15 PDT
Rated:5 out of 5 stars
Hi thelark2020-ga ?

You asked a great question.  I liked the idea that you asked about
"garden variety" flu, because that is the one we have to contend with
each year, like it or not.  I possibly gave you more than you asked
for in my answer, but I sum it up at the end.


Flu is caused by a single family of viruses, called appropriately the
influenza viruses.  They infect animals and the respiratory tract of
humans to cause (generally awful) symptoms.  Usually people feel as if
they are sick all over with coughs and sneezes, muscle aches, fever,
headaches, fatigue. (Although "stomach flu" is a viral sickness, it is
not caused by the influenza virus.) For most people, respiratory flu
lasts less than a week and there are no lasting effects. ( )

"The single best way to protect against the flu is to get vaccinated each fall."
( ) But you can also
reduce the risk of catching a flu virus by washing your hands
frequently during the flu season, especially when you've been out in
public; by avoiding  putting things like pencils in your mouth; by not
biting your nails.  In general, it is wise to keep your hands away
from your face. ( ). 
The flu virus has to get into your nose or mouth to cause problems.


In general, a person with the flu starts shedding the virus about 24 -
48 hours before the appearance of symptoms.  At this point, the virus
is in low concentrations. The infectious period peaks after the onset
of symptoms, usually in 24 to 48 hours. Then concentrations decline
and are undetectable by day 5 after the onset of

Viruses landing on a hard, nonporous surfaces like steel or plastic 
have been shown to live for about 24 to 48 hours. During this time,
viruses on such surfaces die off, so their concentrations (and ability
to cause illness) diminish considerably by the 48 hour mark.  Even at
24 hours, it is unlikely that they would be transferred to a hand
touching the object.

Other vectors of transmission may be contaminated hands or other
surfaces.   Tissues, cloth and paper may harbor viruses under certain
conditions for about 8 to 12 hours.

In general, it is thought that viral transmission from surfaces would
require high concentrations such as those existing in nasal secretions
in early stages of the flu. ( ).

The most common way of getting the flu is airborne transmission of flu
particles via sneezes and coughs.

To sum up: To get the flu as a result of touching a doorknob, the
following would probably have to occur within 24 hours: an infected
person in the early stages of the illness would have to wipe his nose
with his hand, then touch the doorknob; and a second person would have
to touch the doorknob, then bring his hand up to his face.

That's not to say it couldn't happen, but points to the wisdom of
frequent hand-washing.


New flu strains occur every year.  Viruses are constantly mutating and
they evolve quite rapidly into organisms that can cause symptoms in
animals and humans.  Once this happens, they are transmitted from
animal to animal or human to human.  Sometimes there is a shift in
that the virus that originally infected an animal can now infect a
human.  This is the basis of the current Bird Flu fear.

Since people who get the flu develop immunity to that strain, the
virus generally dies out each year.  A new strain may develop the next
year or over the next several years.

"Although an influenza epidemic can occur at any time of year, flu
season in temperate regions typically begins with the approach of
winter?November in the Northern Hemisphere, April in the Southern
Hemisphere. Flu viruses spread more easily during cold weather because
people tend to spend more time crowded together in homes and schools,
as well as buses, subways, and other places with poor ventilation...."
( )


1.  If a person catches the flu on Monday, symptoms would probably
develop by Wednesday (24 to 48 hours) and the most contagious period
would probably be Friday or Saturday (24 to 48 additional hours).

2.  A flu virus will live on a doorknob for 24 to 48 hours, but the
likelihood of getting the flu from a doorknob is much less than being
sneezed on by a person with the flu.

3.  In the temperate zones the winter months offer the best
environments for transmission: closed rooms, and other enclosed spaces
like subways, cars, and buses.  The flu virus doesn't go anywhere for
the rest of the year.  It dies out each year and a new virus evolves
the next year (with a rare exceptions).

Here are some web sites that may interest you:


Findings at Baylor College of Medicine/Flu

Self Care Center/Colds and Flu

Google search Strategy:
search terms: flu transmission

search terms: flu fomites

search terms: flu transmission

search terms: flu symptoms

I really enjoyed doing the research for this question.  I hope I gave
you the answers you wanted.  Thanks for using Google Answers.

All the best, 

thelark2020-ga rated this answer:5 out of 5 stars and gave an additional tip of: $5.00
Yes, you gave me more than I asked for and it was much appreciated. 
Thank you for doing a very thorough job.

Subject: Re: Questions about influenza.
From: onenonblonde-ga on 10 Apr 2006 21:14 PDT

Very nice answer.  Good Job!

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