BOSTON — Routine AIDS testing of all young and middle-aged patients at hospitals where AIDS is relatively common could identify as many as 110,000 Americans who are infected with the virus but don’t know it, a federal report says.

Researchers estimated that in one year their plan would identify about 11 percent of all Americans who carry the virus. The idea is to find these people early so they can both benefit from early treatment and guard against infecting others.

About 1 million Americans are thought to be infected with HIV, the AIDS virus, and about one-fifth of them are hospitalized annually. However, about two-thirds are treated for conditions unrelated to AIDS and most presumably don’t know they are infected.

The report, written by Dr. Robert S. Janssen and colleagues from the U.S. Centers for Disease Control in Atlanta, was published in Thursday’s New England Journal of Medicine.

In 1990, 225,000 HIV-infected people were cared for in the nation’s 5,558 hospitals, the researchers estimated. They said if all 25 million patients were tested, 163,000 with unsuspected infections would have been identified.

However, many oppose such broad-scale testing because it would mean checking many people who are at minuscule risk of the virus. Instead, the CDC proposal is an alternative that focuses on those in the age groups and locations where the chances are highest of finding unsuspected infections.

The authors suggest routine, voluntary HIV testing of all patients between ages 15 and 54 who are seen in hospitals that have one or more newly diagnosed AIDS cases for each 1,000 discharges. This would mean testing about 3 million people nationwide, and it would identify 110,000 unsuspected infections.

Dr. Timothy Dondero, a co-author of the report, said the analysis “is something less than outright recommendation” by the CDC, although “we would anticipate that some hospitals may be encouraged to consider this seriously.”

In an editorial in the journal, Dr. Thomas C. Quinn of the National Institute of Allergy and Infectious Diseases said routine AIDS testing in hospitals makes sense.

“With all the improvements in survival and quality of life for HIV-infected persons, it is imperative that patients be given the opportunity to be routinely counseled and tested for HIV,” he wrote.

However, he noted that such a program would carry costs and responsibilities: More lab tests, more counselors for those who test positive, and safeguards to keep results confidential.

Dr. Roy Widdus, executive director of the National Commission on AIDS, said the CDC plan “is a defensible part of a big strategy if it’s handled correctly.”