STOCKHOLM, Sweden — Three European scientists shared the 2008 Nobel Prize in medicine today for separate discoveries of viruses that cause AIDS and cervical cancer, breakthroughs that helped doctors fight the deadly diseases.

French researchers Francoise Barre-Sinoussi and Luc Montagnier were cited for their discovery of human immunodeficiency virus, or HIV, in 1983.

They shared the award with Germany's Harald zur Hausen, who was honored for finding human papilloma viruses that cause cervical cancer, the second most common cancer among women.

U.S. researcher Dr. Robert Gallo was locked in a dispute with Montagnier in the 1980s over the relative importance of their roles in groundbreaking research into HIV and its role in AIDS. Gallo told The Associated Press that he was disappointed at not being included in the prize.

Montagnier told the AP in Abidjan, Ivory Coast, where he is attending an international AIDS conference, that he was still optimistic about conquering the disease.

The prize, he said, "encourages us all to keep going until we reach the goal at the end of this effort."

Montagnier said he wished the prize had also gone to Gallo.

"It is certain that he deserved this as much as us two," he said.

Zur Hausen, a German medical doctor and scientist, received half of the 10 million kronor (US$1.4 million) prize, while the two French researchers shared the other half.

Zur Hausen discovered two high-risk types of the HPV virus and made them available to the scientific community, ultimately leading to the development of vaccines protecting against infection.

The U.S. Food and Drug Administration approved the vaccine Gardasil in 2006 for the prevention of cervical cancer in girls and women ages 9 to 26.

The vaccine works by protecting against strains of the human papillomavirus, or HPV — including the two that zur Hausen discovered — that cause most cases of cervical cancers. The HPV virus, transmitted by sexual contact, causes genital warts that sometimes develop into cancer.

"I'm not prepared for this," zur Hausen, 72, of the German Cancer Research Center in Heidelberg, told the AP by telephone. "We're drinking a little glass of bubbly right now."

In its citation, the Nobel Assembly said Barre-Sinoussi and Montagnier's discovery was one prerequisite for understanding the biology of AIDS and its treatment with antiviral drugs. The pair's work in the early 1980s made it possible to study the virus closely.

That in turn let scientists identify important details in how HIV replicates and how it interacts with the cells it infects, the citation said. It also led to ways to diagnose infected people and to screen blood for HIV, which has limited spread of the epidemic, and helped scientists develop anti-HIV drugs, the citation said.

"The combination of prevention and treatment has substantially decreased spread of the disease and dramatically increased life expectancy among treated patients," the citation said.

Barre-Sinoussi said that when she and Montagnier isolated the virus 25 years ago they naively hoped that they would be able to prevent the global AIDS epidemic that followed.

"We naively thought that the discovery of the virus would allow us to quickly learn more about it, to develop diagnostic tests — which has been done — and to develop treatments, which has also been done to a large extent and, most of all, develop a vaccine that would prevent the global epidemic," she told the AP by telephone from Cambodia.

Gallo, director of the Institute for Human Virology at the University of Maryland and a prominent early researcher in HIV, said it was "a disappointment" not to be honored along with Montagnier and Barre-Sinoussi.

But he said all three of the award's recipients deserved the honor. No more than three people can share a Nobel Prize.

His dispute with Montagnier reached such a level in 1987 that then-President Ronald Reagan and Prime Minister Jacques Chirac of France penned an agreement dividing millions of dollars in royalties from the AIDS blood test. The settlement led to an agreement that officially credited the Gallo and Montagnier labs with co-discovering the virus.

In the 1990s, however, the U.S. government acknowledged that the French deserved a greater share of the royalties. The admission solidified the French position that Montagnier had isolated the virus in 1983, a year before Gallo.

Maria Masucci, member of the Nobel Assembly, said there was no dispute in the scientific community that the French pair discovered and characterized the virus.

Dr. Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases in Bethesda, Maryland, agreed there's no doubt the French scientists first identified the virus. He said they, and zur Hausen, deserved the Nobel.

Fauci said that if additional researchers could have been included, Gallo "would have been an obvious choice to be added to that list."

That's because of Gallo's roles in showing that HIV causes AIDS and in the technical advance that allowed the isolation of HIV, Fauci said.

The Nobel Assembly said zur Hausen "went against current dogma" when he found that some kinds of human papilloma virus, or HPV, caused cervical cancer. He realized that DNA of HPV could be detected in tumors, and uncovered a family of HPV types, only some of which cause cancer.

The discovery led to an understanding of how HPV causes cancer and the development of vaccines against HPV infection, the citation said.

Barre-Sinoussi, 61, is director of the Regulation of Retroviral Infections Union at the Institut Pasteur in France, while Montagnier, 76, is the director for the World Foundation for AIDS Research in Prevention, also in the French capital.