MINNEAPOLIS - At first glance, Sexpulse looks like a sexually explicit gaming Web site, with provocative pictures of nude men, cartoons and cheeky icons. But it's not a game. Far from it.

The Web site, in development at the University of Minnesota, is the newest strategy to slow a second wave of the HIV/AIDS epidemic rising among young gay and bisexual men.

Infection rates in that population have increased by an alarming 12 percent annually since 2001, federal officials reported last month. What's different about that age group and that time period? The Internet, for one.

Gays and lesbians were among the first to create online social sites in the late 1990s. Like all such sites with their chat rooms and detailed profiles, places such as Gay.com and Manhunt.net have proven extraordinarily efficient venues to find sexual partners.

Experts debate whether the Internet is driving risky sexual behavior, but one thing is clear, they say: To stop the epidemic, they have to go to where those connections are being made - which is less and less often in gay bars and neighborhoods, and increasingly online.

That's why professor Simon Rosser and others at the University of Minnesota's School of Public Health are using a $3.5 million federal grant to create Sexpulse, a prototype for online HIV intervention specifically for gay men.

"If this is successful, it is huge," Rosser said. "We can flick a switch and make it available to every gay man in the world."

The implications, however, are far broader than HIV and the gay population. If it works, it could pave the virtual way to influencing all kinds of health-related behaviors - from diabetes control to personal finance - online.

Decline, and then a tick upward

HIV and AIDS among gay men peaked in 1984. Then it declined.

But starting in the late 1990s, the number of cases, especially among young men, began to tick upward. Researchers have identified a number of reasons. The advent of highly effective antiviral drugs means the disease is hidden. Most young men never witness its terrifying consequences.

"When I first came out, I went to a bar, and someone pointed at a guy and said 'he's HIV-positive,' " said Rick Weinmeyer, 28, a gay man who works on Rosser's research projects. "It floored me to realize that it still existed."

Andy Birkey, an outreach worker for the Minnesota AIDS Project who surfs gay Web sites as safersexboy, said many of the young men he talks to know that HIV is a sexually transmitted disease. But they don't know what that means, exactly. "The most common question I get is, 'Can it be transmitted through oral sex?' " He tells them that it's high risk for some sexually transmitted diseases, but low risk for HIV.

Party drugs, especially methamphetamine and alcohol, also play a big role in driving impulsive, unsafe behavior.

Today, many young gay men never get tested for HIV and don't even know that they are positive. One 2005 study of 5,000 gay men ages 15 to 29 found that 1 in 10 were infected, but three-fourths of that group didn't know it.

Nor do teens and young men know how or when or if to ask about someone's HIV status.

"Young people who are coming out who are 18 or 19 don't have those skills," said Dr. Gary Remafedi, an expert on adolescent health and HIV at the U who works with Rosser.

Then there's the Internet that accelerates everything.

Gay.com, the grandfather of gay Web sites, is a broad community where gay men share many aspects of their lives. But with 8.6 million personal profiles, it is also a place where they connect for sex.

Other sites, such as Manhunt.net and Adam4Adam.com and the men-seeking-men section of Craigslist, are more sex-oriented. Many of those kinds of sites promote healthy behavior and safe sex, but a quick tour with Birkey illustrates the problem. One man says he's HIV-negative and seeks "safe sex only." Another says "anything goes." Another offers "party favors" - code for methamphetamine.

A lot of research has tried to determine if such Web sites accelerate HIV rates by somehow encouraging unsafe sex.

Rosser and Remafedi say no. They recently published a study comparing behavior of men who find partners on the Internet to those who find them in gay bars or elsewhere, and then to those who do both. Those who use both were the most likely to engage in risky sex.

But Rosser said the Internet appears to be having an indirect effect. The number of infections may be rising, in part, because the Internet increases the sheer number of sexual encounters by gay men, he said.

In short, it's efficient. But that can work both ways. "The technology is not the problem. But it may be the solution," Remafedi said. "Millions of people are using the Internet to meet partners, so it's a wonderful venue to intervene."

Changing people's behaviors

The intervention is, of course, a Web site. But not your ordinary health Web site.

A lot of health education Web sites are "Debbie Downers," said Michael Allen, chief executive officer of Allen Interactions. The company is working with Rosser and other experts at the university to build the site. "They Ãother Web sitesÄ are constantly trying to scare you or tell you how bad things are," Allen said.

Sexpulse is different. It's fun, funny and designed to change behavior both through education and boosting self-esteem, Allen said - the model he uses for all kinds of e-learning.

"If we don't change people's behavior, we are not doing anything that matters," he said.