Someone with a cold may just have left a little
drop of virus on the light switch for you to
pick up and infect yourself with, researchers
found in a real-life look at how colds get passed
Adults with runny noses leave the virus on
about 35 percent of objects they touch, such
as telephones, door handles and television controls,
the researchers at the University of Virginia
reported on Friday.
An hour after someone leaves a virus-infected
droplet on a surface, it can be picked up 60
percent of the time. And 24 hours later, 33
percent of the little virus-laden droplets got
onto a finger, the researchers told a meeting
of the American Society of Microbiology.
"Some adults left a few ... and some contaminated
almost all of the sites tested," said Dr. Owen
Hendley, a professor of pediatrics at the University
of Virginia Health System, who led the study.
Although the study was funded by the makers
of a disinfectant spray, Hendley said it is
far more important for people to remember to
wash their hands.
"In order to get infected with the rhinovirus
which causes essentially half of the colds in
adults and children, you have to get the virus
on your fingertip and then you stick in your
own nose and your own eye," Hendley said in
a telephone interview.
His team wanted to study just how often this
actually happens. So they put an advertisement
in the Charlottesville, Virginia newspaper seeking
people with colds.
They found 15 who were infected with rhinoviruses
and asked them to spend the night in hotel rooms.
The volunteers were asked to move around the
room, sleep there, and get up and spend two
hours in the room before checking out. The researchers
then asked them to point to several places they
"Of the 150 sites that they pointed out to
us, 52 had virus on them, which is 35 percent,"
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"The common sites were the light switch, the
hotel pen, faucet handles, the door handle,
the TV remote and the telephone," he said.
Two of the volunteers left no virus anywhere.
"Then there were three bad boys in there. We
found virus on eight of the 10 sites which we
sampled," Hendley said.
Other studies have shown that some people are
"super-spreaders" of certain infections.
"Whether they were real snotty or they were
sloppy, I don't know," he said. "We weren't
in there watching them."
Then the researchers did a second phase.
"Because there is virus on a surface, that
doesn't mean that you are going to be infected
with it," Hendley said.
The researchers had saved mucus samples from
each volunteer. Several weeks later, they put
little drops of their mucus on surfaces in hotel
rooms. Some they let dry for an hour, some were
left for 24 hours.
"Each person was exposed to his or her own
mucus," Hendley said -- ensuring they would
not become ill again.
"We asked them to flip on a light switch or
to dial the 9 on the telephone or to hold the
telephone handset," Hendley said.
Then they tested each volunteer's fingers.
One-third of the time, a volunteer picked up
virus from touching an object in a room where
the virus had been drying for a full day.
In room where the virus had dried for an hour,
the volunteers picked up virus 60 percent of
"So your husband could leave it there for
you and go to work and you could by chance turn
on a light and if you then put it in your nose
and your eye and get infected," Hendley said.