SAN FRANCISCO — Consider this: The average woman with AIDS survives 15 1/2 weeks from diagnosis to death. The average white gay man lives 39 months.

You have heard of AIDS as a disease of homosexuals, hemophiliacs and intravenous drug addicts. But acquired immune deficiency syndrome is becoming a disease of women — who are being diagnosed later than men and dying sooner.

Consider:

Women are the fastest growing group in the country infected with HIV, the AIDS virus; their numbers increased by 45 percent last year alone, according to a study by researchers from Hahnemann Hospital in Philadelphia.

Their survival time from diagnosis to death is half that of men in general and one-tenth that of white gay men.

Their death rate from AIDS quadrupled from 1985 to 1988. The federal Centers for Disease Control in Atlanta has declared AIDS “a leading cause of death in women of reproductive age.” It is the leading cause of death for women ages 25-34 in New York City.

Thirty-one percent of the more than 13,600 U.S. women with AIDS got the disease through heterosexual intercourse, says the CDC.

Women have about 10 percent of the 132,140 known AIDS cases in the country, up from 6 percent in 1982. The CDC has cited intravenous drug use and bisexuality as factors in areas with high female infection rates.

Women are virtually excluded from federal drug testing, representing only 6.6 percent of the patients in programs that provide the latest AIDS treatments.

“I want to know why we are dying so quickly,” said Catherine Ritter, a New Yorker with AIDS. “I want to know why we are being ignored. I want to know what is going on with women and AIDS in America.”

Ritter found few answers at the Sixth International Conference on AIDS in San Francisco earlier this year. Virtually all the presentations dealt with gay men, drug addicts and children.

But some preliminary answers are emerging:

For every case of heterosexual AIDS transmission from an infected woman to a man, there are 12 cases of heterosexual transmission from an infected man to a woman, researchers from the University of California, San Francisco, reported.

It is unclear what mechanisms — biological or social — account for this pattern, said epidemiologist Dr. Nancy S. Padian.

Women do not believe they are at risk. More than 40 percent of the women now infected did not know they had engaged in high-risk behavior, according to a study released here by the Johns Hopkins School of Medicine in Baltimore.

“Often women don’t know the sexual history and AIDS risk of their sexual partners,” said Marguerite Barbacci, an AIDS researcher at Johns Hopkins.

Physicians also fail to diagnose AIDS in women because they do not think of if as a women’s disease and little is known about AIDS symptoms specific to women. Late diagnoses shorten survival time.

“No eyebrow of suspicion is raised when a woman gets pelvic inflammation that won’t go away, has an abnormal pap smear, persistent urinary tract infections or genital warts,” said Risa Denenberg, a nurse practitioner and one of the authors of a book, `Women, AIDS and Activism,” due out next month.

“Everything that should tip people off is being ignored because people just don’t know. Women are dying of AIDS without ever having been diagnosed.”

Even when they are diagnosed with AIDS, women often don’t meet the official criteria of having the disease. The definition of AIDS established by the CDC is based on a specific level of destruction to the immune system or on the onslaught of specific diseases categorized as opportunistic infections.

“It is very frequent for a woman’s first … symptoms to be gynecological,” said Denenberg, “but the list of opportunistic infections is based only on male … patients.”

Chronic candida yeast infection in the mouth, for example, is defined as an opportunistic infection, but chronic candida yeast infection in the vagina is not.

A study by the University of Medicine and Dentistry in Newark, N.J., indicates that early diagnosis and treatment, with emphasis on gynecological problems, can extend the lives of women with AIDS.