Mathilde Krim in 2012. She was the founding director of Amfar, the Foundation for AIDS Research. (Evan Agostini/AP)

Mathilde Krim, a geneticist and virologist who bridged the worlds of laboratory science and political activism to strip AIDS of stigma and turn its treatment into a national cause, died Jan. 15 at her home in Kings Point, N.Y. She was 91.

Her death was announced by Amfar, the Foundation for AIDS Research, where she served as founding chairman. The organization did not give a cause.

Dr. Krim was researching the possible treatment of leukemia with interferon, a protein and antiviral agent, when in 1980 a physician friend told her he was seeing a set of unusual symptoms affecting gay men in New York. Their lymph nodes were enlarged, as were their spleens, but the men appeared to be free of disease.

As Dr. Krim and the physician, Joseph Sonnabend, began testing blood samples, their patients started to die — marking some of the first reported deaths of an American epidemic and what has since become a global health crisis.

"I was struck by the totally misguided stigma — obviously due to age-old prejudice and to ignorance of biological facts — that was being attached to the disease," Dr. Krim later said, recalling AIDS's early designation as "gay cancer" or "the gay plague."

Dr. Krim had been known as the "Interferon Queen" for her single-minded research into the protein's medical potential, but quickly pivoted to research of acquired immune deficiency syndrome. The disease was found to be spread by a virus, HIV, and while early patients were often gay or drug addicts, Dr. Krim worked to dispel a broad misconception that it was confined to patients of a certain sexual orientation or social status.

Actress Elizabeth Taylor is flanked by fellow actress Natasha Richardson, left, Dr. Krim, right, and Paul Stevens, an executive with Continental Airlines, during a 1996 news conference at the United Nations. (MARTY LEDERHANDLER/AP)

With a $100,000 donation from her husband, politically connected movie mogul Arthur Krim, she co-founded the AIDS Medical Foundation in New York in 1983. The organization merged with a similar California-based group two years later to form Amfar, the American Foundation for AIDS Research, and adopted its current name in 2005 in a nod to its increasingly global scope.

Dr. Krim was chairman of the organization's board from 1990 to 2004, by which time AIDS — at least in the United States — was treated largely as one disease among many others. Yet for much of the 1980s, AIDS was so stigmatized that Dr. Krim could not post her organization's name on a sign in the lobby of its office building (it was shortened instead to "A.M. Foundation") and struggled to raise money from larger organizations. Still, she approached the problem with a zeal and focus that recalled an earlier period of her life, when she smuggled guns across Europe for a Zionist militant group.

A soft-spoken yet forceful champion for AIDS patients, she spearheaded legislation that increased federal funding for research into the disease, called for expanded access to experimental drugs and promoted the use of condoms and needle exchanges in an effort to limit the disease's spread.

Crucially, she also enlisted a group of celebrities who helped make AIDS a popular cause across the country. Working with actors such as Elizabeth Taylor, Paul Newman, Woody Allen and Joan Rivers, she organized gala events and fundraisers that raised millions of dollars.

"Mathilde did carry AIDS into the social mainstream," wrote the late Allan Rosenfield, a women's health advocate and dean of Columbia University's Mailman School of Public Health. "She saw that AIDS would demand the intellectual resources of the fields of medicine, basic science and public health, and she set out to bring them to Amfar to guide its research grantmaking, overturning many stereotypical notions of gay men in the process."

President Bill Clinton awarded her the Presidential Medal of Freedom, the nation's highest civilian honor, in 2000.

Although AIDS-related deaths have fallen by 48 percent worldwide since they peaked in 2005, according to the U.N. advocacy program UNAIDS, the disease remains a pandemic. In 2016, the organization reported, about 36.7 million people were living with HIV and about 1 million people died of AIDS-related causes.

Mathilde Galland was born in Como, Italy, on July 9, 1926, and raised in Geneva. Her father was a Swiss agronomist, and her mother was from what was then Czechoslovakia.

She graduated with a bachelor's degree in genetics from the University of Geneva in 1948 and received a doctorate from the school in 1953. Years earlier, moved by newsreel footage that showed the 1945 liberation of Nazi death camps, she also worked as a volunteer with the Irgun, a Zionist paramilitary group, smuggling weapons on bike rides across the France-Switzerland border.

Dr. Krim converted to Judaism and married a fellow gun smuggler, David Danon, before joining Israel's Weizmann Institute of Science, where she helped develop a method for determining an infant's sex before birth. The marriage ended in divorce, and she settled in New York City after her 1958 marriage to Krim, a Weizmann trustee who had served as finance chair for the Democratic Party and founded the movie studio Orion Pictures. He died in 1994.

Dr. Krim joined what is now Memorial Sloan Kettering Cancer Center as a research scientist in 1962 and remained there for more than two decades, leaving in the mid-1980s to focus on her nonprofit organizations.

Survivors include a daughter from her first marriage, Daphna Krim of Bethesda, Md.; a sister; and two grandchildren.

Dr. Krim expressed few regrets over leaving the confines of her lab, noting that while there were many scientists waiting to assume the mantle of research, few were willing — or able — to organize fundraisers with former first lady Rosalynn Carter or director David Lynch.

"I came to the conclusion that it's better if I stay on the outside and help people inside the labs," she told the New York Times in 1988. "I'm not such a genius that somebody else cannot do what I was doing. And these would be people who cannot do what I can."