The use of tampons has been linked to a mysterious and sometimes fatal new disease that most often strikes women under 30, federal disease investigators said yesterday.

The new clue to the cause of toxic-shock syndrome, which occurs during or just after the patient's menstrual period, was reported by investigators for the Center for Disease Control in Atlanta.

New reports of the illness have been mounting rapidly at the center since it published a bulletin May 23 on the disease. Since September 1978, there have been 131 reported cases of toxic-shock syndrome, 10 of them fatal . All but three of the victims were women, including the 10 who died.

Evidence is growing that toxic-shock syndrome is caused by a type of bacteria that enters the blood during or just after the victim's menstrual period, and produces a sometimes lethal fall in blood pressure by means of a toxin (poison) manufactured by the germ.

Now, it appears that the bacteria -- staphylococcus aures -- gets into the bloodstream more easily in women who use tampons, according to Dr. Kathryn Shands, chief investigator of toxic-shock syndrome at the disease control center.

All of the women who have suffered toxic shock were between 12 and 52 years old, and the illness is four times as common in women under 30 as in those over 30.

The tampon connection was discovered by comparing toxi-shock patients to women their age who did not get the disease.

In three studies, researchers questioned 92 victims of the disease. Ninety-one of the women (or 99 percent had used tampons. In two of the studies, this was a significantly higher percentage than was found for women who remained well (86 percent in one study and 76 percent in another), according to Shands.

She said the researchers found no association with any special brand of tampon, or with tampons made of any special material.

The center's report emphasized that using tampons alone does not cause toxic-shock syndrome, so that women who have never had the disease probably need not avoid tampons. Those who do wish to lower their risk, the report said, might choose to use pads, or use tampons for only part of their period.

Investigators do not know how tampons help to bring on the disease. Manufacturers estimate that 70 percent of American women use tampons, yet toxic-shock syndrome appears to be rare, stricking only 3 of every 100,000 women a year, according to the disease control center's report.

Some researchers guessed that tampons may produce "micro-ulcerations" of the vagina through which bacteria can enter the blood, or make it easy for bacteria to grow by blocking blood flow. But Shands said there is no evidence for either theory.

"It may be that the tampon itself enhances growth of the organism or enhances toxin production," she said. "We don't know that."

"We're aware of the report," said a spokesman for the Kimberly-Clark Corporation, which manufactures Kotex tampons. "We . . . are continuing to cooperate with the center in its investigation of the phenomenon."

Manufacturers of other tampon brands could not be reached for comment yesterday evening.

Of the toxic-shock victims who had vaginal cultures done to look for germs, 94 percent were positive for staphylococcus aureus. Only 2 to 15 percent of women in the general population carry the bacteria.

Toxic-shock syndrome begins with seemingly innocuous symptoms -- headache, vomiting, fever and diarrhea -- which most victims discount as a mild virus infection. But within 48 hours many of them develop shock -- or a fall in blood pressure -- severe enough to cause kidney failure and require hospitalization in an intensive-care unit.

At that time, most patients also get a red rash that later causes peeling of the skin on their palms and soles.

Once a woman has had toxic-shock syndrome, she has a good chance of getting it again. In a Wisconsin study, 42 percent of patients had at least one recurrence, usually within a few months during another menstrual period. But the Wisconsin researchers found that treating victims with an antibiotic that kills staphyulococcus bacteria greatly decreased the chance of a second attack.

The disease control center therefore recommends that women who have had toxic-shock syndromw should obtain cultures of the nose and vagina, should take antibiotics if the cultures show the bacteria, and should not use tampons for several months.

Shands said women who think they may have had the disease should write to the center's Toxic-Shock Syndrome Study in Atlanta.

So far, Shands said, there have been seven cases of the disease in this region: one in the District of Columbia, three in Virginia and three in Maryland.