UNTIL RECENTLY, before vaccines and antibiotics, practicing medicine was a much more dangerous business. Physicians faced considerable risk of catching infectious diseases from patients; in epidemics, many died. Scientific advances nearly erased public awareness of the idea that caring for the sick could bring hazard, that it required bravery. Now AIDS has brought it all back.

To the much-observed public statements by some doctors that they would refuse certain kinds of care to AIDS patients if it meant running the risk of infection, medical professional groups and doctors' associations have responded with statements true to the profession's tradition: doctors have an ethical responsibility to care for all the sick; they should safeguard themselves wherever possible against risk, but they must not sidestep it. Now a group of deans of the medical schools of New York State has gone further. Early this month the deans released a draft statement saying that any student, trainee or doctor in a teaching hospital who refused care to AIDS patients should be expelled or dismissed.

The signers come from some of the country's best medical schools. Their action follows strong statements to the same effect by both the American Medical Association and Surgeon General C. Everett Koop. Both of these had stressed the moral obligation of doctors, but neither went beyond that to the question of how or whether to enforce this duty within the profession.

The New York doctors took a large step doing that, and it seems right to us. No one is forced to enter training for the life of a doctor, and patients should be able to assume that their doctors can be relied upon to treat them when they are sick. If medical schools are unequivocal in their commitment to that principle, aspiring doctors can weigh the commitment against the dangers before they start down the path.