I've often wondered how long viruses and other infectious agents can
live outside the human body on a dry surface.

If the bathroom door handle of a really dirty public bathroom is dry,
how likely is it that you could get something bad from it? What if
it's not dry? Can most infectious agents live indefinitely on a damp
door handle or do they require a human body to survive?

If a sick person (let's say they have the flu) sneezes into the air,
how long will it likely be before there is 0 chance of being infected
by breathing air from that room? What if they sneeze in a bathroom
onto a damp surface like a sink faucet handle that stays damp due to
continual usage?

Obviously, most people spend most of their time not sick. So it is
obviously not a huge problem. I'm just wondering how much of that is
due to cleanliness and how much of that is due to viruses and bacteria
just dying before they get a chance to infect other people.

Hello Mnxmatch,

   Whether or not viruses are living organisms or not (I was taught
they are opportunistic parasites, needing a host cell to replicate and
cause us to be sick), they can be spread, as are bacteria, in the
manner you mentioned.

    It would be difficult to time the life of a virus or bacteria in a
bathroom, but bacteria and viruses are spread through droplet
contamination ? a sneeze, or a cough ? which you breathe in and infect
yourself. Simply touching a dirty faucet handle or doorknob won?t make
you sick -- unless  -- you touch your face, mouth, eyes or nose. It?s
at this point that you are infecting yourself. Some bacteria have
outer membranes that are tougher than others? meaning some bacteria
live longer that others, as different viruses have different life
spans outside of a host ? they do like a moist environment, and die
faster on dry surfaces.

  Why some people get sick or not, upon exposure to droplet or door
handles, depends on whether the sneezer/cougher is carrying a
pathogenic virus or bacteria, and whether you infect yourself from
touching your face/mouth/eyes/nose after contact with an infected
item. This is gross, but I remember reading a study once that showed
nose-pickers were sick far more often that those that avoid that nasty
habit!

  Your primary defense against getting sick is your own immune system.
If you are in good health, chances are good that your immune system
will destroy any invading organisms. If you are recuperating from
surgery or an illness, or are tired or run down, or in a state of
stress, you will be more prone to get sick. If you have already been
exposed to any organisms you come in contact with, you will have
antibodies to protect you. However, there are a plethora of different
organisms in our environment, and chances are good we will encounter
some we have never been exposed to, during our lifetime.


   This site explains it best. Please read the entire page for
complete information.
?Microbes can live on household surfaces for hundreds of years. The
good news, however, is that most don't. Some well-known viruses, like
HIV, live only a few seconds.

Microbes, of course, are everywhere. Each square centimeter of skin
alone harbors about 100,000 bacteria. And a single sneeze can spray
droplets infested with bacteria and viruses as far as 3 feet. The
microbial life span depends on many factors, says Philip Tierno,
director of microbiology and diagnostic immunology at the New York
University School of Medicine. Because viruses must invade cells of a
living host to reproduce, their life spans outside are generally
shorter than that of bacteria, which reproduce on their own. Although
viruses can survive outside a host on household surfaces, their
ability to duplicate themselves is compromised?shortening the virus's
life span.

Humidity also makes a difference; no bacteria or virus can live on dry
surfaces with a humidity of less than 10 percent. Any sort of
nutrients?food particles, skin cells, blood, mucus?helps microbes
thrive, which is why your kitchen sponge is a breeding ground.?
http://www.popsci.com/popsci/medicine/a931c4522fa84010vgnvcm1000004eecbccdrcrd.html

?Respiratory syncytial virus enters the body though your eyes, nose or
mouth. It spreads easily when infectious respiratory secretions ? such
as those from coughing or sneezing ? are inhaled or passed to others
through direct contact, such as shaking hands. The virus can also live
for hours on objects such as countertops and toys. Touch your mouth,
nose or eyes after touching a contaminated object, and you're likely
to acquire the virus. An infected person is most contagious in the
first few days after infection, but respiratory syncytial virus may
spread for up to a few weeks after the start of infection.?
http://www.cnn.com/HEALTH/library/DS/00414.html


   Your best bet in a public restroom, to avoid infection, would be to
wash your hands well, and use a paper towel to turn off the faucet.
Peoplle don?t realize they are re-contaminating their hands when using
a dirty hand to turn off the faucet, and the use a clean hand to
handle the dirty faucet! Use the same paper towel to open the bathroom
door! Carry a small bottle of hand sanitizer with you. Don?t touch
your face, mouth, nose or eyes! Try not to worry too much ? just use
good hygiene and stay healthy!


I hope this has helped you! 

Regards, Crabcakes

Search Terms
============
Experience in the health care field
virus life span + counters
pathogenic organisms + live on counters

Great answer. Thanks!

I will leave it to a Researcher to fully answer your question but I
will say that the world is sometimes a difficult place for viruses.
Sunlight and fluorescent light can be particularly rough on some of
them.

It has been argued extensively whether viruses are living organisms.
They are considered non-living by the majority of virologists as they
do not meet all the criteria of the generally accepted definition of
life. Among other factors, viruses do not possess a cell membrane or
metabolise on their own. A definitive answer is still elusive due to
the fact that some organisms considered to be living exhibit
characteristics of both living and non-living particles, as viruses
do. For those who consider viruses living, viruses are an exception to
the cell theory proposed by Theodore Schwann, as viruses are not made
up of cells.
http://en.wikipedia.org/wiki/Virus

This may become an EXTREMELY important question, as the Bird Flu heads
toward the United States. There's an interesting link at

http://www.internet-grocer.net

that the Bird Flu IS headed for us. 

I've often thought that there is a business waiting to be formed which
would sell porous door handles/knobs that would dispense a lotion or
liquid that would kill germs....

Thank you for the 5 stars and the nice tip!
Regards, Crabcakes

The part of answer that hiv lives outside the body for only few secs
is not correct at all. HIV can be found in blood soaked
hankerchief-crusted blood even after 2 days if kept in ambient
conditions.Now whether anyone can be easily infected by contact with
the same is another matter altogether.