Changes in the design of tampons have led to a 93 percent drop in the number of cases of toxic shock syndrome since 1980, when the disease was first linked to tampon use.

Officials at the federal Centers for Disease Control said in a report released recently that 61 cases of the bacterial infection most often associated with menstruation were reported in 1989, compared with 890 cases in 1980.

CDC researchers say that the decrease is real and that the high absorbency of some brands of tampons was largely responsible for toxic shock, a potentially fatal illness characterized by a high fever and a sunburn-like rash.

"Our initial concern was that after the public attention and the media attention went away . . . people were not bothering to report cases," said Anne Schuchat, an infectious disease specialist at CDC.

A study in 1987 that actively sought to locate cases in several states found only one case per 100,000 women between the ages of 14 and 44 -- a 10-fold drop from the 1980 rate, according to Schuchat.

CDC said the decrease in cases was also attributable to the withdrawal from the market of Rely, the brand implicated in many early cases.

At the same time, other brands of tampons became less absorbent, and different materials were used to make them. Those made of polyacrylate, which was used in Rely, were withdrawn in 1985; current tampons are made with cotton or rayon.

The withdrawal of Rely and the drop in the use of high-absorbency tampons "correlate with a marked decrease in incidence of menstrual toxic shock syndrome," the report said, although it remains unclear why those types of tampons increased the risk.