Many young gay and bisexual men who are HIV-positive may not know they have the virus, according to U.S. health officials.

Their study of more than 5,600 men between the ages of 15 and 29 found that more than three-quarters of those who tested positive for HIV were unaware they were infected. Moreover, before being tested, a majority of these men thought themselves at low risk of having the AIDS virus, and half had had unprotected sex with another man during the previous 6 months.

The findings suggest that the HIV epidemic among young gay and bisexual men “continues unabated,” in part because many are unaware of their infection, according to the study authors, led by Duncan A. MacKellar of the Centers for Disease Control and Prevention (CDC) in Atlanta.

He and his colleagues report the findings in the Journal of Acquired Immune Deficiency Syndromes.

The high rate of unrecognized HIV infection seems to stem in part from a low rate of regular testing for the virus, MacKellar told Reuters Health.

Though many men in the study had undergone HIV testing in the past, few got themselves tested regularly. And only a minority of those who were unaware they were HIV-positive had been tested in the past year. It’s recommended that people at high risk of HIV be tested for the virus and other sexually transmitted diseases at least once a year.

The reason for the lack of regular testing is unclear, but the fact that many men in the study believed they were at low risk for HIV may be one factor, according to MacKellar. However, he added, the findings also suggest that limited access to healthcare and fear of testing positive may be important reasons as well.

The study included gay and bisexual men who were recruited from various venues, including bars, parks, cafes and stores, in 6 U.S. cities. The men were surveyed about their sexual behavior, their perceptions of their own HIV risk and how many times they had been tested for the virus. They also gave blood samples for testing.

Overall, 10 percent were found to be HIV-positive, 77 percent of whom had been unaware they were infected.

Because of the study’s recruiting method, the numbers are probably not reflective of gay and bisexual men across the U.S., according to the researchers. Previous household-based studies have, in fact, found lower rates of unrecognized HIV infection.

Still, MacKellar said the fact that so many men in this study were unaware of their infection “underscores the urgency” of increasing HIV testing among young men who have sex with men.

Expanding HIV testing at venues such as clubs and bars may help reach more men with unrecognized infection, the researchers suggest. Health departments and community groups are working to expand such outreach programs and trying to ensure that people actually get their test results by using newer, rapid HIV tests that provide results in 20 minutes.

It is also important for individual doctors to routinely recommend HIV testing to patients who might be at increased risk, according to MacKellar. “CDC is working with providers to make HIV testing a more routine part of healthcare,” he said.

SOURCE: Journal of Acquired Immune Deficiency Syndromes, April 15, 2005.