A very rare strain of the AIDS virus with roots in West Africa has been identified in four Marylanders, marking the first time the virus has been confirmed anywhere in the state.
In announcing the findings, Maryland Health Secretary Nelson J. Sabatini said yesterday that all four were people who had shown up at state-run testing centers in Montgomery County since 1988 to learn if they were at risk for AIDS.
The rare virus, known as HIV-2, behaves in much the same fashion as does HIV-1, the more common virus that has infected an estimated 1 million people in the United States. Both viruses are spread by sexual contact and contaminated drug needles, and both produce a syndrome -- AIDS -- that cripples the immune system and subjects people to an onslaught of deadly infections.
Both viruses can also be spread by contaminated blood products, although Mr. Sabatini and officials with the American Red Cross appeared eager yesterday to head off any fears that the discovery of HIV-2 in Maryland could signal a threat to the blood supply.
"At this point [the precautions] should rule out any blood donor who would have HIV-2," Mr. Sabatini said. "And the incidence is so small that there's no question about the integrity of the blood supply."
Red Cross officials pointed to a recent study showing that the Elisa test, a laboratory procedure used to screen out tainted blood, is capable of detecting the rare HIV-2 strain in 60 percent to 95 percent of the cases where it is actually present.
The blood organization, following a federal Food and Drug Administration mandate, also rejects donors with ties to West Africa. Officials said this precaution should further minimize the risk that any HIV-2 could slip into the blood supply.
Nonetheless, the American Red Cross is planning to implement a new "combination test" that is highly sensitive to both viral strains as soon as it receives FDA approval, said national spokeswoman Liz Hall. A commercial application is now before the agency, which is expected to act within the next few months.
With the Maryland findings, the federal Centers for Disease Control now knows of only 31 cases in the United States of infection with HIV-2; the first case was identified in 1987.
Experts tracking both viruses said yesterday that it could be years before the rare strain takes off in the general population, if it ever does.
So far, all but a few of the 31 cases seen nationally have been West Africans who moved to the United States or Americans who have spent time in West Africa, according to the CDC.
"The data I've seen show it's still pretty rare in the United States," said Dr. Peter Drotman, a medical epidemiologist with the CDC. "HIV-1 has been in the United States for well over 10 years.
HIV-2 was only recently discovered, and almost all of the cases have been pretty much linked to West Africa."
Dr. Joan Gibble, an official with the Chesapeake and Potomac Region of the Red Cross, said another indication of the virus' rarity was a recent study in which 8,000 consecutive donors in Boston and Miami were tested for HIV-2. None carried the virus.
According to Mr. Sabatini, the Maryland cases were found after a blood specimen supplied by a man in Montgomery County in June tested positive in the Elisa test but yielded "inconclusive" results on a more sensitive follow-up HIV test. The health department, seeking to unravel the mystery surrounding the man's blood, then ran a third test designed solely to pick up HIV-2.
The man tested positive.
Health officials, wondering if any other clients at testing sites across the state actually carried HIV-2, gathered 500 stored specimens that had also produced "inconclusive" test results. All were tested specifically for HIV-2. Eight specimens belonging to three individuals tested positive.
Mr. Sabatini said that health officials were able to locate only one of the four people identified in Maryland, a man who had immigrated from West Africa.
The other three have not been located because they did not supply identifying information at the testing sites, where people have the right to remain anonymous.
The state health department has not yet determined if there is any HIV-2 among people who showed up at test sites in Baltimore, because the test centers there are run by the city health department. The two agencies will conduct the same sort of investigation there, Mr. Sabatini said.
Facts about HIV-2
* It is fairly common in West Africa but rare in the United States. With the four Maryland cases, the federal government now knows of 31 cases in the United States.
Just like the more common HIV-1 strain, it is spread by sexual contact, intravenous drug use and contaminated blood products. Both strains cause AIDS.
The Red Cross says studies show that the virus, relatively new to the United States, does not pose a current threat to the blood supply.
* Laboratory tests now employed by blood banks are more effective at screening out HIV-1 than HIV-2. But a new test, awaiting federal approval, is highly sensitive to both viruses.