Nearly a generation after researchers isolated the HIV virus that causes AIDS, there is still no cure for the disease nor a vaccine to protect people from infection. But a new White House strategy to curb the spread of AIDS, and reports this week of an experimental gel that helps reduce the chances of transmitting the virus in women, offer hope that millions of lives can be saved over the next 20 years both in the U.S. and abroad.

The president's plan builds on efforts begun during the Bush administration to encourage people to get tested for the virus and to seek treatment before symptoms appear. For the first time, it also sets clear goals for reducing rates of transmission and infection over the next five years and targets more resources toward the four groups at highest risk of contracting the disease: African-Americans, gay and bisexual men, Latinos and substance abusers.

The experts who drew up the plan note that much of the initial sense of urgency surrounding the epidemic has faded in recent years, leading many people to wrongly assume that AIDS is no longer a public health emergency. But they warn that far too many people still don't know they are infected and unwittingly pass the virus on to others, and that some 51,000 new infections occur every year in the United States. More than 1.1 million Americans are currently living with the disease.

The president's plan aims to cut the rate of new infections by 25 percent over the next five years and reduce transmission rates by 30 percent. It would also increase access to care to enable 85 percent of new AIDS patients to get treatment within three months of being diagnosed, and expand testing to raise the proportion of people who are aware of their infection 90 percent. Currently, only 79 percent of infected people know their status, and only 65 percent of those infected get treatment within three months.

The outlook for Mr. Obama's new strategy may be strengthened by Wednesday's report that researchers in South Africa have developed a vaginal gel that may significantly cut a woman's risk of infection from the AIDS virus. Tests there with a gel containing the antiretroviral drug tenofovir suggest that women who used the gel consistently were only half as likely to become infected with HIV as t Steven McK hose in a control group.

Although the gel would have to be at least 80 percent effective to be licensed for use in the United States, researchers believe that more powerful forms of the medication, coupled with a broad AIDS education and public health campaign, could greatly increase protection for women.

An estimated one in three girls in South Africa is infected with the AIDS virus by the age of 20; researchers calculate the gel could prevent 1.3 million infections there over the next 20 years and save more than 800,000 lives. Worldwide, more than half of the 33 million people living with AIDS are women.

Since taking office, President Barack Obama has been under pressure from gay rights groups to address a range of concerns, including increased funding for AIDS education, prevention and treatment programs as well as repeal of the "don't ask, don't tell" policy that prevents gays from serving openly in the military.

But the White House plan announced last week — and the development of the gel, which public health officials are describing as a major breakthrough in the fight against AIDS — doesn't just affect gays. They point to the possibility of finally bringing under control a scourge that has killed 25 million people worldwide since 1981, and left 18 million children orphaned. Mr. Obama believes that can be accomplished through better coordination of agencies without increasing the $19 billion the government already spends on domestic AIDS programs. If so, the plan could save millions of lives in coming years if officials make the most of the resources available to them and direct them to where the needs are greatest.