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More Clues Come in Possible HIV 'Superbug' Case

Researchers concerned about the speed with which the virus strain replicated

THURSDAY, March 17, 2005 (HealthDay News) -- Researchers report they have started to unravel some of the many mysteries surrounding the recent appearance of a possible HIV "superbug" in a New York City man.

It's still not completely clear, however, whether this is the "nightmare virus" that some tabloids have predicted or a phenomenon more closely linked to the genetic idiosyncrasies of the patient.

"The study doesn't quite answer whether it's the virus or the host," said Dr. Bob Shafer, an assistant professor of medicine at Stanford University, who also maintains the Stanford HIV Drug Resistance Database.

Regardless, state the authors of the report, which appears in the March 19 issue of The Lancet, the case is "of concern." The man is known to have been promiscuous, and what also troubles the scientists is the fact that this mutated strain replicated as quickly in the lab as potent strains that haven't been exposed to the antiretroviral drugs that often prompt the virus to mutate in the first place.

"Most of the time when HIV has mutated in the past, the virus has become less virulent or less aggressive," explained Dr. Joseph Baran, an infectious disease specialist at Scripps Mercy Hospital in Chula Vista, Calif. "It's still there and will do damage, but it's slower."

"What alarmed the investigators [in this case] is that the virus had multiple mutations, multiple drug resistance and, for some reason, the person had a very rapid course of infection," he added.

Although the identity of the man is unknown, he is in his late 40s and had unprotected sex with multiple male partners, often while using the street drug crystal methamphetamine. The man had repeatedly tested negative for HIV between September 2000 and May 2003.

In early November of 2004, he developed a fever, sore throat, weakness and fatigue for about a week. The symptoms initially went away, but recurred a few weeks later. In mid-January, he reported a sore throat, difficulty swallowing, severe fatigue, weight loss and lack of appetite. An HIV test came back positive.

The man believed that he became infected in the third week of October 2004, although it's possible he contracted the virus 20 months before developing symptoms. He continued to have sex with about 10 partners until the end of December, when his health started declining.

Experts do not yet know if this case is an isolated one, but the existence of multiple partners led doctors to notify the New York City Department of Health and Mental Hygiene. City health officials, in turn, held a press conference and issued a public health alert on Feb. 11, 2005. The publicity drew criticism from experts who felt there was not enough information to signal an alarm about a possible supervirus.

The jury is still out on this question.

For The Lancet report, researchers at the Aaron Diamond AIDS Research Center in New York City analyzed the genetic makeup of the patient's virus.

This particular virus, it turned out, is resistant to multiple classes of drugs, replicates extremely quickly and is associated with a rapid decline into full-blown AIDS (in four to 20 months). The virus has multiple mutations, making it resistant to most available drugs, the researchers said.

Drug-resistant HIV is not unheard of. "About 1 to 2 percent of new cases in the U.S. have resistance to more than one drug or several drug classes," Shafer said.

Nor is rapid progression from infection to disease a rarity. Although it typically takes nine to 10 years for the virus to cause symptoms, the timing does vary widely. Previous research has indicated that the likelihood of progression to AIDS in six months is seven per 10,000 individuals and, in 12 months, the likelihood is 45 per 10,000 individuals.

Although HIV is highly variable from person to person, it is usually not the virus that determines the characteristics of a case, Shafer noted. "Usually, it's the host or host-virus interaction," he said. "There are about 10 to 15 host genetic factors associated with the risk of progressing rapidly, but even those factors only explain about 30 percent of the variation in risk to progression."

The authors of this study did not look at all 10 to 15 factors, Shafer pointed out. And even if they had, there would still be other, unknown variables.

Still, "they didn't really uncover any factors in this person that might have contributed to him having a fast disease," Baran stated.

All of this leaves experts unsure as to how worried to be.

"I would not put this as great a threat as what's going on with avian influenza in Southeast Asia, where emerging strains have about an 80 percent mortality," Shafer said. "On the other hand, I wouldn't downplay it either. We have to remember that the current HIV epidemic, which infects about 40 million people, began just about 100 years ago from a single cross-species transmission."

"If people are not careful and don't take measures to avoid infection, there's nothing to say that 20 years from now we couldn't have an epidemic within an epidemic," he continued. "It's not of immediate risk but if we don't take measures, 20, or even five to 10, years from now, we'll be very sorry."

Baran put it another way: "This guy had sex with a lot of people and, if this turns out to be a superbug, then we've got a problem."

More information

Learn more about AIDS from the National Institutes of Health.

SOURCES: Bob Shafer, M.D., assistant professor, medicine, Stanford University, Palo Alto, Calif.; Joseph Baran, M.D., AIDS specialist, Scripps Mercy Hospital, Chula Vista, Calif.; March 19, 2005, The Lancet
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