By Lee Bowman
- Scripps Howard News Service
The virus
that causes AIDS can remain alive and well in syringes with infected
blood for at least 42 days when kept in near-freezing temperatures,
according to a new study by Yale researchers.
But when stored
above room temperature, or hotter than about 80 degrees, there's
a less than 1 percent chance that a syringe will still contain
viable samples of the human immunodeficiency virus (HIV), the
study found.
The study,
published in the journal Substance Use and Misuse, was conducted
to help assess the various risks that drug injectors might face
when they share or reuse discarded needles.
"Behaviors
of injectors vary tremendously, '' said Robert Heimer, an associate
professor of epidemiology and public health at the Yale School
of Medicine. "Some injectors rapidly discard syringes when
they are done, mostly out of fear of being spotted by police.
Improperly discarded syringes can be reused and can transmit the
virus.
"But
this research shows that depending on the temperature, you can
decrease from weeks to just one day the period of time for which
syringes can spread the virus.''
Heimer said
the information is important not only to substance abusers but
to police, fire and emergency medical personnel who regularly
come in contact with used needles and are at risk for accidental
needle sticks.
The study
may also be useful to public health and medical workers in the
developing world, where needle recycling is common.
Earlier research
at Yale had found that HIV survival in syringes was strongly linked
to the volume of blood left in a syringe and the duration of storage
at room temperature.
"We were
really surprised that no one had studied this issue before in
the decades this virus has been a public health concern,'' Heimer
said.
In the new
study, researchers loaded syringes with HIV-infected blood, then
fully depressed the plunger to remove almost all the blood, and
then stored the syringes at various temperatures for periods of
one day up to six weeks.
Then, the
residual contents of the syringes were introduced into a tissue
culture that allowed HIV to proliferate.
At 39 degrees
Fahrenheit, 50 percent of all syringes contained viable HIV after
42 days of storage, the longest period tested.
At room temperature,
or 68 degrees, the longest that syringes with infected blood tested
positive was 21 days. HIV capable of replicating was found in
8 percent of those syringes.
And above
80 degrees, and at temperatures up to 98.6, less than 1 percent
of syringes contained viable HIV after one week.
"The
practical implications of these findings are that when people
do not have access to clean syringes, storing used syringes in
warmer temperatures decreases the likelihood of HIV transmission,''
Heimer said.
While warmer
temperatures may knock back the HIV in used needles, that still
doesn't make them safe. They're still even more likely to harbor
liver-damaging hepatitis B and hepatitis C viruses in even larger
quantities - 10 to 20 times more in the same volume of blood -
than HIV and for an unknown period of time.
"No one
knows how persistent (hepatitis C) is because, again, no one has
studied it,'' Heimer said. "We'd like to, but so far we haven't
been able to get anyone to support the lab work with a grant.
Yet we know that (hepatitis C virus) is much more infectious among
drug users than HIV."
Other studies
have shown that 90 percent of IV drug users are infected with
hepatitis C after six years of injecting, compared with 15 percent
who are HIV-positive.
Heimer added
that his findings highlight the benefit of needle-exchange programs,
which allow drug users to turn in used needles in return for sterile
syringes.
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