NEW YORK (AP) _ The discovery of a new virus that may be one cause of multiple sclerosis has produced a wide range of reactions from researchers who have searched for years for viruses or other abnormalities that could trigger the disease.

''It would be a very provocative finding,'' if it is confirmed by other scientists, said Dr. Stuart Cook of the University of Medicine and Dentistry of New Jersey. He has investigated the possibility that measles virus might be related to multiple sclerosis.

''There's a debate among people in the field as to whether one virus causes this disease or multiple viruses,'' Cook said. ''My own personal view is that the evidence favors one virus, although it's still an open question.''

Dr. William Sibley of the University of Arizona believes that the disease is probably caused by a breakdown of the immune system, the body's defense against disease, in which the immune system mistakenly attacks the patient's own brain and nerve cells.

Earlier this year, he showed that common viral infections could trigger multiple sclerosis flare-ups in people with the disease, but he said he doubts that the disease is directly caused by a virus.

He has spent 15 years trying to isolate an infectious agent that could pass the disease among baboons and chimpanzees, with no success. However, multiple sclerosis could be caused by a virus that does not survive in animals, he said.

One of the authors of the new report, Elaine DeFreitas of the Wistar Institute in Philadelphia, acknowledged the uncertainty.

''There have been several reports of viruses being associated with multiple sclerosis in the past,'' she said. ''This is clearly just one of many. It is unclear at the moment whether this is any more or less important than the other viruses that have been suggested.''

There is a hint, however, that this virus could be different. It infects certain cells of the immune system called T-4 cells, a kind of white blood cell. Thus this virus could conceivably explain both the immune system abnormalities seen in multiple sclerosis and the evidence suggesting it is caused by a virus, DeFreitas said.

''It bridges the gap between the immunologic theories of multiple sclerosis and the viral theories of multiple sclerosis,'' she said.