In a major shift of policy, the USA federal government recommended yesterday that all teenagers and most adults have H.I.V. tests as part of routine medical care because too many Americans infected with the AIDS virus don’t know it, reports the New York Times today.

The recommendation, by the Centers for Disease Control and Prevention, urges testing at least once for everyone aged 13 to 64 and annual tests for those with high-risk behaviour.

Dr. Julie Gerberding, the disease control agency’s director and a doctor who treated some of the first San Francisco AIDS patients in 1981, said: ”Our traditional approaches have not been successful. People who don’t know their own H.I.V. status account for 50 to 70 percent of all new infections. If they knew, they would take steps to protect themselves and their partners.”

About 40,000 Americans are newly infected each year, a number that has been remaining steady. In contrast to the early days of the epidemic, which struck gay men the hardest, many of those now infected are black or Hispanic teenagers and were infected by heterosexual sex. The agency estimates that 250,000 Americans, a quarter of those with the disease, do not know they are infected.

The proposal is a sharp break from the early days of the AIDS epidemic, when the stigma of the disease and the fear of social ostracism caused many people to avoid being tested.

That led to heated debate about whether positive test results could be shared by medical and governmental authorities in their effort to contain the epidemic by reaching out to partners of those who might be infected.

The new guidelines, if adopted, would move the agency toward its ”ultimate goals,” which Dr. Gerberding defined as: no more H.I.V.-infected children, no one living for years without antiretroviral treatment and, eventually, no more new cases of the disease.