The number of adults age 50-plus living with HIV/AIDS has been growing in recent years, with the group accounting for 24 percent of people with the infection in 2005, up from 17 percent in 2001, according to CDC.

As to reasons why more seniors are living with HIV, "One of them is the success achieved with medications," said Dr. Anthony Japour, an infectious-diseases specialist at Miami's Jackson North Medical Center and adjunct professor at Florida International University's Herbert Wertheim College of Medicine.

"For me the emergence of AIDS was like the Third World War, due to the number of people dying every day," said Japour, whose medical studies began in 1981. "By the time I finished my studies in 1986, it was already known that HIV was the cause of AIDS. Yet there was no treatment." More recently, people could "be infected with HIV in their 30s or 40s and still live longer than 50 or 60 years," Japour said.

Earlier diagnoses are also being made, Japour said. "To have HIV nowadays doesn't mean a sure death. Virus patients are dying from other causes such as heart problems, dementia or cancer, among other diseases."

In addition to HIV, sexually active seniors may also be at risk of contracting other STDs.

"The older generation has this idea that condoms are only used to prevent pregnancies and they don't use it because they are no longer worried about them," Japour said. "However, even at age 80, you should use a condom if you are sexually active. Now, with medications like Viagra, people remain sexually active until a very advanced age. It is important for doctors to emphasize the use of condoms to older people."