IN THE early stages of the AIDS epidemic, questions were raised about how health care workers could protect themselves against contracting the illness through contact with patients' contaminated blood. Universal testing of patients was rejected not only because it was clearly unnecessary in most cases, but because it was also impractical. There is not time, for example, to test emergency room patients before treating them. In addition, the virus doesn't show up in tests for the first few months after a person is infected, so negative results might be misleading. Finally, a real concern was that identified AIDS victims might suffer discrimination in hospitals and be offered less than adequate care.

Instead of mandating universal testing, the government, with the concurrence of the medical establishment, published guidelines for dealing with all patients in situations where blood loss is a factor. The guidelines suggest, for example, that gloves be worn whenever a health care worker is likely to come into contact with blood or bodily fluids, that waterproof gowns and protective eyewear be worn during surgery and that all needles and sharp instruments be disposed of in special containers. These precautions have the added benefit of protecting care givers against other diseases such as hepatitis. Nevertheless, to date 37 health care personnel have contracted AIDS from infected patients.

Transmission in the other direction -- from doctor to patient -- was not thought to be significant until last July, when a Florida dentist revealed he had AIDS and recommended that all his patients be tested. One woman was found to have the virus. She is the first and so far the only patient believed to have contracted the disease from a health care worker. Last year a doctor in Tennessee died of AIDS, and that state's health department tested 616 of his patients. Only one was HIV positive, but he was an intravenous drug user who had been exposed before his contact with the doctor. Last month, a Baltimore surgeon died of AIDS, and Johns Hopkins University Hospital has offered to test all his patients. No results have yet been announced.

An infected doctor has no legal obligation to alert his patients or to stop practicing, but certainly he has a moral responsibility to take steps to protect them. Mandatory testing of all health care workers doesn't make sense because tests provide no assurances for the future. But surely, as officials at Johns Hopkins now recommend, infected employees have a moral obligation to reveal their condition to the hospital and comply with whatever restrictions are placed on their practice. In the aftermath of the Johns Hopkins incident, the Maryland Hospital Association has asked state health officials for guidance on protecting patients from infected medical personnel. These recent cases suggest that the subject deserves review by medical associations and federal agencies as well.