The federal Centers for Disease Control and Prevention yesterday urged that people newly diagnosed with human immunodeficiency virus (HIV) infection be reported to state health departments by name, rather than by coded number.

A name-based system, which is the traditional method of disease surveillance, will give public health officials the simplest and most efficient way of tracking the HIV epidemic, the federal agency believes. Some AIDS advocacy organizations worry, however, that the strategy will discourage some high-risk people from being tested out of fear that the results won't remain confidential.

All states require doctors and hospitals to report the names of people newly diagnosed with AIDS, the advanced stage of HIV infection, to public health departments. By law, the names are kept in confidence by the departments. However, state epidemiologists use them to contact physicians to get information, such as how the person was exposed to the virus, that is useful in charting trends.

The CDC now wants states to collect data not just on people ill with AIDS, but also on people who test positive for HIV but are still healthy. Thirty-four states already do so, using name-based surveillance. Four states use a code that uniquely identifies a person without using a name.

In Virginia, doctors and laboratories report people with newly positive HIV tests by name. In Maryland, they are reported with a number that encodes age, race, sex and part of the person's Social Security number. The District does not collect any data on new cases.

Although CDC officials say in the guidelines that they prefer name-based systems, they say coded ones also are acceptable. In any case, the recommendations are not compulsory, though the agency provides an incentive for HIV surveillance by providing money to states that choose to do it.

Better data on HIV infection, and not simply AIDS, are urgently needed because AIDS data alone are no longer a good reflection of who is getting infected and how. Such information is crucial to devising prevention and treatment programs.

In the past, little could be done to slow a person's progression from HIV infection to AIDS. Consequently, gathering data on AIDS cases gave epidemiologists an accurate--if out of date--picture of what was happening at the front end of the epidemic. Now, many people treated with combination antiviral drugs never progress to AIDS. AIDS data alone provide little information about trends among the newly infected.

"It is beginning to be like driving a car without a map," said Robert Janssen, the CDC's director of HIV/AIDS surveillance. "The general consensus on the need for HIV data really came about in the last two to three years, because of the huge effect of [new] treatment."

One of the main advantages of a name-based system, Janssen said, is that it lets public health officials efficiently make certain they aren't counting more than once people who have had multiple positive HIV tests. It also makes it easier for doctors and clinics to locate a patient's record and provide more demographic information, if requested. Under a code-based system such as Maryland's, this can be done, but a clinic or hospital first has to decode the number, and then trace it to a name.

The CDC guidelines strongly support public funding of anonymous HIV testing, which provides little useful epidemiological information but may be the only thing that persuades some people to be tested and subsequently enter treatment.

Terje Anderson, policy director of the National Association of People With AIDS, said the guidelines are "a step in the right direction," although the organization prefers coded systems. However, because up to one-third of HIV-infected people don't know they are infected, Anderson believes the CDC should rely less on surveillance, and more on such things as risk-group sampling, to learn about the contemporary epidemic.

Ronald Johnson, an official of Gay Men's Health Crisis in New York, said the organization is "very disappointed" in the emphasis on named reporting.

"We have very real concerns that a names-based system can be a deterrent to testing. It's more of an issue than the guidelines would suggest," he said.

The CDC estimates that 800,000 to 900,000 Americans are infected with HIV and that about 620,000 are aware of their infection.