Officials Find Rare HIV Strain in L.A. Woman

A Los Angeles County woman has been identified as the first person in the United States to carry a rare form of the AIDS virus, a discovery that federal health officials said will prompt changes in AIDS testing to protect the nation’s blood supply.

Current tests for the human immunodeficiency virus detect the unusual strain in just four out of five cases. The woman infected with the strain--known as Group O--repeatedly tested negative for HIV, both with conventional blood tests and more sophisticated DNA analysis.

Officials at the federal Centers for Disease Control and Prevention and at the Food and Drug Administration, which licenses AIDS tests, stressed that Group O poses little, if any, current threat to the blood supply. But they said tests for the virus must be reconfigured to better detect Group O--a process that will take about a year.

The woman, whose identity is being withheld, is in her early 20s and immigrated to the United States from a nation in West Africa, where the Group O strain is found more often than elsewhere, although it is also not common there. The woman was apparently infected in her homeland.

She was discovered several months ago by epidemiologists at the CDC as part of a records search launched two years ago after Group O first turned up in Europe. The discovery was a bit of a fluke; the woman had been recorded as an HIV carrier even though her tests had registered negative.

The agency issued a public report of its finding Thursday, characterizing the discovery as a tip-off that Group O could become a future public health threat. “This is really a sentinel event,” said Dr. John Ward, who heads the CDC’s effort to track HIV and AIDS.

The report comes as the 11th International AIDS Conference is about to get underway in Vancouver, Canada, this weekend. CDC officials said they expect to announce the findings in a “late-breaking presentation” there.

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New tests to detect Group O pose a technical challenge to manufacturers, who must devise screenings that are sensitive to Group O but do not lose sensitivity to more common strains.

“This is really prevention,” said Jay Epstein, director of the FDA’s blood research program. “It’s not that we’re patching up a problem; it’s the other way around. We had an early warning and we’re reacting to it appropriately.”

While Epstein said there is no evidence that Group O has spread in the United States, the woman has had one sexual partner since arriving in the country. Los Angeles County health authorities are trying to track him down so he can be tested.

“That is definitely something we are very concerned about,” said Dr. Peter Kerndt, director of Los Angeles County’s AIDS surveillance program. “We want to know if there is any transmission here.”

Group O was first identified in West Africa in 1989 by scientists charting the genetic makeup of HIV; they found the virus had marked genetic differences from the more common Group M strains that are responsible for the worldwide AIDS pandemic.

In the years since, about 100 cases have been studied, and as best experts can tell, the disease progresses in the same manner with both strains.

It is now estimated that between 5% and 7% of those infected with HIV in certain West African nations, such as Cameroon, carry the Group O strain. In 1994, doctors reported that nine patients in France--eight of whom had emigrated from West Africa--carried Group O. That year, the CDC began the search that led to the Los Angeles County woman.

The woman might never have been discovered if county health officials had followed technical guidelines for reporting AIDS cases to federal officials. Her case was reported as AIDS based on the results of blood tests that showed she had a low level of CD4 cells, the immune system cells crucial to fighting the AIDS virus. But the report should not have been filed, given that her HIV tests turned up negative.

“It is completely an accident that she was reported,” Kerndt said.

The woman came to the United States in 1994. In November 1995, she visited Dr. Leora Britvan at Kaiser Permanente’s medical center in West Los Angeles with symptoms that resembled AIDS. She had already been tested for AIDS in Africa as well as at another Los Angeles area hospital and the tests turned up negative.

Britvan administered another HIV test, but the results were unclear; the doctor described them as “weakly positive.” A second, more sophisticated test, came back indeterminate. A final test, which detects HIV through its genetic makeup, came back negative.

But when Britvan ran tests to look at the woman’s CD4 cells, she found that they were low--an indicator that the patient was infected. To Britvan, an internist who had never heard of the rare Group O strain, it was a medical mystery--a “diagnostic dilemma.”

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In March of this year, Britvan received an unexpected call from CDC officials. They had combed through the National AIDS Registry--a list of all AIDS cases reported since 1981, roughly 500,000 people, two-thirds of whom are dead--and found 91 people who had emigrated from West Africa, including Britvan’s patient. The woman’s name was included in the registry only because of the earlier Los Angeles County report.

When they tested her blood specifically for the Group O virus, the mystery was solved. The patient, meanwhile, has been treated with antiviral drugs.