In an age of wonder drugs for erectile dysfunction, it might be no surprise that people are sexually active well into their 80s. Outreach worker Sharri Thompson says she is reminded about that almost every day.

Yesterday, Thompson was outside the senior-focused Eleanor Roosevelt Apartments in Aliquippa as part of National HIV Testing Day, giving out free hot dogs and hamburgers and trying to recruit seniors in the building to get tested for HIV.

As a coordinator for Life and Liberty Inc., an Ambridge faith-based organization that conducts HIV-prevention campaigns, Thompson is concerned that the incidence of HIV and AIDS is increasing in southwestern Pennsylvania's senior population.

She's not alone.

Locally and nationally, experts are increasingly concerned about anecdotal and statistical evidence that a growing population of older Americans are living with HIV and AIDS. They say the widespread availability of drugs like Viagra allows men to be more sexually active than in the past, and that many older Americans do not use protection because they're not worried about pregnancy, or don't know that their behaviors put them at risk for an illness they once thought could only affect gay men and drug users.

Nationally, the number of AIDS cases among Americans older than 50 increased fivefold between 1995 and 2003, said Gina Focareta, communications director for the Pittsburgh AIDS Task Force.

In Pennsylvania, the number of people living with AIDS who are older than 65 increased from 71 to 133 between 1998 and 2002, and the number of people over the age of 55 living with AIDS increased from 283 to 487 in that same period, according to data from the state Department of Health.

Although some of the increase can be explained by the expanding length of time that people can live with AIDS and HIV because of better treatment, the number of new cases also is rising.

In Pittsburgh, people 50 and older have accounted for around 12 percent of all AIDS cases since 1981, according to the county Health Department. But some advocates are guessing the number will rise because of the size of Allegheny County's senior population, which is the second-largest in the country outside of Palm Beach County, Fla.

"We just know it's going to hit us because of the demographics," said Doyin Desalu, executive director of the Southwestern Pennsylvania AIDS Planning Commission. "With Viagra and with the population that really didn't need to practice safe sex when they were younger, they don't realize the impact of risky sexual behavior."

The organization runs outreach and prevention initiatives in some senior high-rise apartment complexes in the area, and speaks to a number of older residents who might be putting themselves at risk for HIV.

In particular, residents talk about seeing younger women -- few call them prostitutes -- around the developments and in the apartments of older single men around the same time that Social Security checks come in.

But married men also are practicing unsafe sex, said the Rev. Kenneth G. Crumb Sr., who founded Life and Liberty Inc., the organization giving HIV tests to seniors in Aliquippa yesterday. He hears talk in barbershops of men in their 70s and 80s who don't leave home without their Viagra, and who visit street women and then go home and sleep with their wives.

Few programs target older people when talking about prevention.

There are almost no age-specific HIV education programs regionally, and prevention messages don't depict older adults as people at risk for HIV and sexually transmitted diseases, said Grace Kizzie, a research specialist at the Pennsylvania Prevention Project, an HIV-prevention program based out of the University of Pittsburgh Graduate School of Public Health.

There are few prevention initiatives because most people don't like to think that people older than 50 are sexually active, Kizzie said.

Kizzie and colleague Emilia Lombardi conducted a series of focus groups for women 50 and older about HIV and AIDS. The women in the focus groups were, for the most part, shocked to hear that they could be at risk for HIV, Kizzie said.

There also is likely a population of older people who are HIV-positive and don't know it. HIV in older people is often misdiagnosed as just aging because many of the symptoms are the same, said Focareta of the Pittsburgh AIDS Task Force.

Jane P. Fowler, 69, of North Kansas City, Mo., was shocked when she found out that she was HIV-positive in 1991. She only had one sexual partner -- her husband -- until she was 50, when she started dating again after getting divorced.

She had heard about HIV but thought it was a disease only for gay men. She didn't use protection because she wasn't worried about getting pregnant, and never suspected that her new partner could be HIV-positive.

The former journalist founded HIV Wisdom for Older Women, a Kansas City-area outreach program, and is trying to educate older women about the importance of protection if they start dating again either as widows or after a divorce.

"These people just don't understand the sexual realities of today," she said. "You think you know so and so for years, you might think you know him, but maybe he's sowing his oats, maybe he's seeing men on the side, maybe he's visiting a prostitute."