Because of an editing error, it was incorrectly stated in the first sentence of an article yesterday that a new strain of the AIDS virus had been discovered. The sentence should have said a new virus had been discovered. (Published 6/3/87)

Dr. Robert Gallo, one of the discoverers of the AIDS virus, reported yesterday that he had discovered a new, related strain in 10 Nigerian AIDS patients, and predicted that others will be found in the future.

Gallo's address at the opening session of the Third International conference on AIDS here described the original AIDS virus, known as human immunodeficiency virus or HIV-1, as the most virulent member of an expanding family of viruses. All of them cause lifelong infection in humans and are capable of destroying the immune system.

Gallo emphasized that the discovery of the new, unnamed virus and recent reports of a West African AIDS virus known as HIV-2 did not signal a major shift in the epidemic. "There's one real AIDS epidemic. There's one real AIDS virus," he said at a news conference. "Don't get confused with new names and new groups as equal new dangers."

But Gallo and other researchers at the conference said that the emergence of an expanding family of viruses capable of causing acquired immune deficiency syndrome and other illnesses complicated the development of blood tests and vaccines, and made it more difficult to predict how the disease might spread in the future.

The AIDS virus and its West African cousin are members of the family known as retroviruses. The new virus, isolated in about 10 AIDS patients in rural Nigeria, apparently is not closely related to the other members of the family, Gallo said. "There is no reason to believe it's anywhere else now {but Nigeria}," he said.

Strains of the West African virus, variously called HIV-2 and HTLV-4, have been found in many West African countries but rarely, if at all, in Europe and the United States, Gallo said. Researchers differ about how dangerous this virus is. "It looks like it can cause AIDS . . . but with less efficiency than the real AIDS virus," Gallo said.

Gallo previously discovered two viruses in another branch of the family, known as HTLV-1 and HTLV-2, both of which can cause leukemia but are much less easily transmitted from person to person than the AIDS virus. Gallo said these viruses can also cripple the immune system, but rarely do so.

The leukemia-causing viruses are of greater concern in the United States. Recent studies in some cities show high rates of infection with these viruses in drug addicts, raising the likelihood that they could contaminate the blood supply and spread the viruses to others via transfusions, Gallo said.

HTLV-1 can cause leukemia or disease of the nervous system, but only very rarely. Only about one percent of those infected develop these illnesses, Gallo said. However, the virus can remain latent in the body for as long as 30 years before producing disease, he said.

In an interview, Gallo estimated that "a few million Americans" are probably infected with the HTLV-1 virus. He said that in an National Institutes of Health study by Dr. Stanley Weiss, 34 percent of drug addicts in New Orleans and Queens had positive blood tests for HTLV-1 or HTLV-2. Lower but still significant rates were found in Newark, Jersey City and Camden, N.J. Some addicts were found to be infected with both the AIDS virus and one of the leukemia-causing viruses.

Gallo said blood-banking organizations should consider routine testing for HTLV-1 and HTLV-2 because of the risk of their being transmitted through contaminated blood. "We believe that a diagnostic test . . . could be made for all the leukemia viruses," and another test developed that would screen for all the AIDS-causing retroviruses, he said.

Gallo said that all of the human retroviruses probably originated from African monkey viruses that mutated and became capable of infecting humans at different times in history. "We must keep open the probability of continuing to find new human retroviruses," he said. "We must not panic . . . . That we have the capacity to find others at an early stage should be encouraging, not discouraging."

Gallo said no one had yet found a vaccine that could protect test animals against infection with the AIDS virus, but added that he believed such a vaccine was "very much possible." He said there had been progress in identifying two or three parts of proteins in the virus that are common to many different strains.

One or more of these key parts could be used as the target for a vaccine that would allow the body's immune system to recognize the AIDS virus and fend off infection. The extreme variation among different strains has been a major stumbling block in the vaccine search.

In another report presented yesterday, a study of Belgian heterosexuals infected with the AIDS virus and their sexual partners suggests that the virus may be passed as efficiently from women to men as vice versa. This contrasts with earlier reports, said Dr. Peter Piot of the Institute of Tropical Medicine in Antwerp.

Initially, 70 percent of women who were sexual partners of infected men developed positive blood tests for the virus, while only 36 percent of men who were partners of infected women did so, Piot said. But researchers subsequently were able to culture the AIDS virus from 45 percent of the male partners whose blood tests were initially negative, and from 9 percent of the female ones.

Piot suggested that it may take longer for a man infected by a woman to show the infection through a positive blood test than vice versa, because the dose of virus transmitted may be smaller.

Ultimately about 80 percent of both male and female sexual partners in the study became infected, he said.