STOCKHOLM, Sweden — Three European scientists shared the 2008 Nobel Prize in medicine on Monday 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. He told The Associated Press that he was disappointed at not being included in the prize.

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.