Scientists have identified a Los Angeles-area woman as the first person in the United States known to carry a rare strain of the AIDS virus, a finding that will force changes in HIV screening tests to protect the nation’s blood supply.
The rare form of HIV, called Group O, escapes detection by current antibody tests in about one of every five cases, the Centers for Disease Control and Prevention reported Friday.
Antibody tests failed to detect the virus in the Los Angeles County woman even though she had what appeared to be AIDS symptoms. The woman, who immigrated to the United States from West Africa in 1994, was found to be HIV-positive only after the Atlanta-based CDC performed more sophisticated tests.
“There’s every indication, based on AIDS surveillance evidence, that this is an exceedingly rare condition in the United States. In fact, this is the only case that we’re aware of,” said Dr. Patrick Sullivan, a member of the CDC’s HIV tracking team.
Manufacturers of HIV tests are working with the Food and Drug Administration, which licenses the tests, to produce kits that more accurately detect Group O. Current tests detect the more common form of the virus, Group M, with an accuracy greater than 99 percent.
Improved tests should be available within a year, said Dr. Jay Epstein, director of FDA blood research.
“The blood supply is no less safe today than it was yesterday because of one report of one case,” he said.
Researchers said Group O doesn’t appear to be any deadlier than the more common strains of HIV.
There is no evidence that Group O has spread in the United States, and the woman in her early 20s has had one sexual partner since arriving in the country two years ago, Epstein said. Health officials are trying to find him so he can be tested.
Group O was first identified in West Africa in 1989. It differs genetically from the Group M strains responsible for the AIDS epidemic.
The Los Angeles County woman tested negative for HIV using the current antibody test and a DNA test, Sullivan said. Still, she exhibited AIDS symptoms such as a low level of CD4 cells, the immune-system cells that fight HIV.
In October 1995, doctors checked the woman again because of persistent lymph node swelling and extremely low levels of T lymphocytes - classic symptoms of AIDS. An AIDS antibody test showed “weakly reactive” results, and a more sensitive and specific kind of test called a Western blot yielded “indeterminate” results, according to a summary of the case in the CDC’s Morbidity and Mortality Weekly Report.
A highly sensitive “PCR” test that looks for pieces of the virus itself, rather than antibodies against the virus, was negative. Nonetheless, because of the woman’s symptoms and contradictory test results, local health officials entered her on a list of AIDS cases, a practice not uncommon in California according to CDC epidemiologist Patrick Sullivan. That allowed CDC officials to recognize her as a potential Group O case when they were conducting a survey for such cases last year by looking at records of people with AIDS from Central and West Africa.
Specialized tests by the CDC showed that the woman was indeed infected with Group O HIV.
xxxx TEST NEEDED Officials said plans are under way to improve commercial tests so they will be able to detect the unusual AIDS variant known as Group O. But fewer than 100 cases of Group O infection have been definitively diagnosed worldwide, and almost all of those have been in Central and West Africa, where an estimated 6 percent of all AIDS cases are believed to be Group O.