Naming viruses can get almost as complicated -- and competitive -- as finding them.

With prestige, prizes, publications and patents at stake, scientists often feel the pressure to be first.

The discovery of the virus now known as HIV-2 is no exception.

What Dr. Myron (Max) Essex, a leading Harvard virologist, calls a "slightly sordid chapter" in international AIDS research took place last year.

Essex was in Washington that spring to address the annual meeting of the American Society of Microbiology. He was planning to reveal the details of his lab's discovery of HTLV-4 -- a new AIDS-related virus in West Africa.

The work had been accepted for publication in Science magazine and was due out the next week. Science told Essex he could discuss the new virus in his talk but not before.

The day before his speech, Essex got a phone call from a reporter with the French newspaper Le Monde. Dr. Luc Montagnier, the leading French AIDS researcher, had scheduled a press conference at a small scientific meeting in Lisbon the next day, reportedly to announce discovery of a new AIDS-related virus in West Africa. Did Essex have any comments?

Essex called Science and asked permission to break the magazine's embargo so he could talk to the reporter. The magazine refused.

That same day, in Lisbon, Montagnier announced isolation of a new virus, which he called LAV-2, in two West African AIDS patients being treated in Europe. As outlined by Montagnier, the virus was remarkably similar to the one Essex's group had hinted at months earlier at an international meeting in Brussels and in the medical journal Lancet and was about to describe in detail in Science.

In fact, both groups now agree, the two viruses are probably the same.

But Montagnier had found it in two AIDS patients; Essex had never seen it in a case of AIDS.

While some reporters leaped on Montagnier's claim as possibly the early hints of a second AIDS epidemic, Essex urged caution. Montagnier had cited only two cases and couldn't prove that their illness was caused by the virus. Hundreds of HIV-2-infected prostitutes Essex's group was studying in Senegal appeared uniformly healthy.

Relations between French and U.S. AIDS researchers already were touchy. The dispute between Montagnier and Dr. Robert C. Gallo of the National Cancer Institute over who was the first to discover the AIDS virus had even reached the courts.

Gallo said it was "unorthodox at best" for Montagnier to announce a new virus on the eve of Essex's scheduled speech, without having mentioned it at any other scientific meetings.

"We were stunned," says Dr. Jean-Loup Romet-Lemonne, a colleague of Essex's.

Montagnier could not be reached for comment. A spokeswoman for the Pasteur Institute in Paris said Montagnier's announcement in Lisbon had been planned "for more than a month" and called its timing -- hours before Essex's talk -- a coincidence.

Asked whether Montagnier had known of the Essex group's forthcoming article in Science, the spokeswoman said, "I don't think so."

The day before his Washington speech, Essex sent reporters copies of his talk with instructions that it not be released until the next afternoon "unless a similar story about which we've heard rumors from Paris" appeared earlier. After Montagnier's announcement, Essex immediately released his speech.

But Montagnier, in Essex's words, had "outjockeyed" the Harvard team.

"People are going to read a headline that says 'New Virus Causes AIDS,' " said Dr. Richard Marlink, another Essex colleague. "They're not going to read a headline that says 'New Virus Found in Healthy People: Problems Unknown.' "

Terminology compounded the confusion. Essex initially called his new virus HTLV-4 and Montagnier called his LAV-2. Later, in a move initiated by Montagnier, international scientists agreed to call them both HIV-2.

"It's clear now that serologically we're talking about the same thing," Essex says.

There are several possible explanations for the discrepancy between the findings of Essex and Montagnier. One is that Montagnier was finding AIDS patients who just happened to be infected with HIV-2, as large numbers of West Africans are. Another is that HIV-2 comprises several strains, some more pathogenic than others. A third is that HIV-2 can cause AIDS-like disease -- but only rarely, in perhaps 1 percent of cases or less.

Essex says the third explanation seems "the most realistic" and "would best fit both of our patterns of results." But, he adds, "we have no evidence for it on a statistical basis -- it's just that we can't rule it out."

Montagnier, meanwhile, has not discouraged the idea that he alone discovered HIV-2.

In the New England Journal of Medicine last May, he reported finding HIV-2 in 30 patients, 17 of whom had AIDS. Almost all the patients were from West Africa. At the end of the article, Montagnier mentioned the "recent" isolation of HTLV-4 in healthy Senegalese by Essex's group, adding, "we assume that it is identical to HIV-2."