- WASHINGTON (Reuters) - More
than three-quarters of all U.S. patients with the AIDS virus have an infection
that resists one or more of the drugs used to treat it, researchers reported
on Tuesday.
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- They said the grim news meant that drug-resistant HIV
had spread even faster than was feared, and the lifesaving cocktails of
drugs that help many patients lead normal lives were becoming increasingly
limited in their usefulness.
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- Unless better drugs are developed soon, or until a vaccine
is invented that can control the virus, patients will have ever-lessening
chances of using drugs to counter AIDS, the researchers told a conference
sponsored by the American Society of Microbiology.
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- Some already have no chance at all, Dr. Douglas Richman
of the Veteran's Administration hospital and the University of California
in San Diego, who led the study, said.
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- "A number of these patients are not readily treatable,"
Richman said in a telephone interview.
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- Richman and colleagues tested blood samples taken in
1999 from 1,647 men and women. They used a test made by South San Francisco-based
ViroLogic Inc. (NasdaqNM:VLGC - news) to test how the virus responded to
the many available drugs used to test HIV.
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- "They reflect almost 209,000 people and about 130,000
who have detectable viremia (levels of virus in the blood)," Richman
said.
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- Of these, Richman's team told the Interscience Conference
on Antimicrobial Agents and Chemotherapy in Chicago, 78 percent carried
virus that resisted at least one drug. "Just over 50 percent of them
were resistant to more than one class of drugs," Richman said.
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- HIV EVOLVING TO RESIST DRUGS
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- Other studies had shown that HIV was evolving to evade
nearly every drug available, but these are the most startling numbers yet.
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- "Many of the previous studies were relatively small
and in highly selected populations, so that accurate estimates were not
possible," Dr. Samuel Bozette, who worked on the study, said in a
statement.
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- Bacteria are known to mutate to resist drugs, which is
why new antibiotics are being developed regularly.
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- But Richman said a virus such as HIV is trickier than
any bacteria. "The reason is this virus replicates to higher levels
at faster rates, so it evolves faster," he said.
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- "Once resistance is there, it stays in a patient
for the rest of his or her life. You don't get cured of an HIV species."
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- With bacteria, it is often possible to take a patient
off antibiotics and so-called wild-type bacteria will eventually move in
and push out the drug-resistant versions. Not so with HIV, which lurks
in the body for decades, perhaps forever.
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- HIV has no cure and is always fatal, but mixes of drugs,
known as highly active antiretroviral therapy (HAART) can keep patients
alive and living near-normal lives for years.
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- There are four classes of these drugs available, each
of which attacks HIV at a different point, and a mixture is required to
make it work. The timing and composition of this cocktail is an art for
AIDS doctors.
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- Richman said the study showed that doctors will have
to start testing their patients right away to see if they have been infected
with a resistant version of HIV.
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- "We have to use drugs more intelligently. This is
the responsibility of physician and patient," he said. "We have
to try to figure out ways to prevent transmission ... and we have to find
drugs to work against resistant virus."
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- Preventing transmission is also difficult. Reassured
by news about the success of HAART over the years, many people see HIV
as a treatable illness and are indulging in risky behavior such as having
unprotected sex, researchers have said.
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- They are ignoring advice to use condoms, despite reports
in recent years that as many Americans are getting HIV as ever before and
warnings that the drugs would not work forever.
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- "We identify two to three new (HIV) patients every
week and if anything, things are getting worse," Richman said.
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- About 40,000 people are infected with HIV every year
in the United States, with half the cases in people under 25.
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