Scientists working with the AIDS virus at the National Institutes of Health, upset by an announcement late Thursday that a second laboratory worker has become infected, said yesterday that the agency's measures to safeguard workers handling the virus are inadequate.

They also expressed anger that the infected worker, who first had a positive blood test in May 1986, was not notified of the result until last week.

Scientists working with the virus at laboratories on the NIH campus in Bethesda said laboratory workers have no formal training in handling the AIDS virus and that safety inspectors make no routine checks of workers' laboratory practices. They said the first laboratory experience of some new NIH medical researchers sometimes is working with the AIDS virus.

"Biological safety has never been taken seriously at the NIH," said one scientist. "We're going to have to keep working under these terrible conditions until more people {in laboratories} get infected."

Dr. Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, said yesterday that NIH officials are investigating why the worker and others at the agency were not told promptly about the positive blood test, performed as part of a research study monitoring laboratory workers handling the virus.

"It was a delay that certainly shouldn't have happened," he said. He added that the incident will trigger a reevaluation of how those working with the virus are trained and supervised and of how results of tests to detect AIDS antibodies in the blood of laboratory workers are communicated. He said officials are reviewing results of the various studies of workers handling the virus to make certain other positive results have not gone unreported.

Fauci noted that the two cases of infected workers have both occurred in outside laboratories that were producing highly concentrated solutions of the AIDS virus under NIH contracts. Such solutions contain many thousands of times the concentration of virus found in blood or other tissue specimens from patients with acquired immune deficiency syndrome.

He said studies of health-care workers and researchers studying AIDS under more routine conditions "have shown clearly that the risk is very, very low." But he added, "I don't think we should be complacent."

Health and Human Services Secretary Otis R. Bowen confirmed yesterday at a meeting of business leaders in Hot Springs, Va., that the infected worker was not informed promptly. "The individual who failed to do the informing once they knew it was positive has been reprimanded," he said.

Government guidelines for AIDS research specify that laboratories producing large amounts of concentrated virus must use biosafety-level 3 equipment -- designed to contain the virus within the lab -- and to be certain that lab workers do not carry the virus outside the lab accidentally. Most AIDS research on the NIH campus involves less concentrated solutions of virus and is done in level 2 laboratories, which have fewer built-in containment features.

Workers who handle the virus are instructed to wear gowns and rubber gloves. They work at hoods, enclosed counters with an air stream that carries any spilled particles upward into a filter.

After the first case of an infected laboratory worker was reported last month, a team of safety experts from the NIH, the Centers for Disease Control and other institutions traveled around the country visiting level 3 laboratories. At a meeting last week in Atlanta, they decided that current safety procedures were adequate, according to Dr. Robert McKinney, director of NIH's division of safety.

A Washington Post reporter visited three level 2 AIDS laboratories on the NIH campus this week. All were so cluttered with equipment that there was scarcely room to walk. None had a shower nearby in case of an accident or spill. Paper gowns and disposable rubber gloves were available, but there were no surgical masks or goggles.

One AIDS researcher said the rubber gloves often broke or leaked. He said that on one occasion he had found broken glass in a hood used to work with the virus. On another, he said he had seen coworkers operating a machine to break up cells containing the AIDS virus on an open counter when it should have been used in a hood to prevent particles from escaping into the air.

Another researcher said he thought the current recommendations are adequate but are not enforced. He said there was no formal training for those working with the AIDS virus. He said radiation-safety officials at NIH often make unannounced visits to laboratories but that biological safety experts never do. "They don't monitor your daily practices," he said.

Those interviewed emphasized that they think that the laboratory conditions posed no danger to the general public, but said they are very unhappy with the way the cases of the two infected workers have been handled. They said that there has been no door-to-door inspection of AIDS laboratories on the Bethesda campus and no attempt to contact all AIDS researchers at NIH to explain how the cases occurred.

"Laboratory workers working at NIH have to read it in the newspaper," said one scientist. "That shouldn't be the way information is disseminated to the responsible scientific community."