The number and rate of AIDS cases reported in the Washington area have increased relative to other metropolitan areas in the last year, according to newly released figures by the federal Centers for Disease Control.

The Washington area now ranks fifth in the number of AIDS cases, behind the New York, San Francisco, Los Angeles and Miami areas. The Washington area's incidence of the disease -- the number of cases relative to population -- ranks it seventh in the nation.

A year earlier, the number of local AIDS cases placed the area seventh in magnitude and eighth in incidence, according to federal tallies.

"The cases aren't leveling off," said Selma DeLeon, AIDS coordinator for the District. "We had a steady increase throughout 1985."

Although the CDC lists the Washington area as having 520 cases of acquired immune deficiency syndrome as of Monday, DeLeon said there are actually 545 cases. The difference represents cases that have not yet been reported to the federal center. Of the 545 persons with AIDS, 284 have died, she said.

In a related development, George Washington University Medical Center announced that it is now affiliated with the Whitman-Walker Clinic, the area's health clinic for the gay community. The clinic is the first of its type in the nation to win university affiliation.

The link is expected to strengthen the university's reputation as a center for AIDS treatment and research. Officials of both facilities said it may also help the clinic in its search for malpractice insurance coverage. Whitman-Walker is one of four local health centers that have been caught in a national wave of insurance cancellations of medical providers.

Whitman-Walker is the only outside clinic associated with the university. In the last year the GW medical center opened its own clinic in the Adams-Morgan area to serve the Hispanic community, as well as clinics serving flight crews and the public in National and Dulles airports.

"There's a sense from George Washington management to get more involved in community programs," said Dr. Jorge Rios, chairman of the university's department of medicine. "That's why we moved into Adams-Morgan."

Whitman-Walker, which began as a men's venereal disease clinic in the Adams-Morgan area 15 years ago, has led the area in AIDS counseling, treatment and testing.

A key part of the District's AIDS efforts, the clinic recently was granted $250,000 to expand and continue its clinical and social work. An additional $80,000 in city funds will help the clinic expand its housing program for people with AIDS.

Under a three-year agreement, doctors at Whitman-Walker will become part of the faculty at the university, gain admitting privileges and participate in university research projects.

The university is now searching for a medical director of the clinic, whose $62,000 salary will be shared equally by the university and the clinic.

Rios said the university is looking for a doctor trained in epidemiology who is interested in treatment and research involving both AIDS and the health of the local Hispanic community.

The doctor must be "gay-sensitive," noted Jim Graham, administrator of Whitman-Walker. "It's not just a physician for AIDS, but someone involved in our alcoholism and venereal disease programs."

Graham said the latest federal AIDS figures demonstrate that "people need to recognize the dimensions of the problem. It's growing."

The number of AIDS cases in the Washington area increased 84 percent in the last year, the same rate experienced nationwide. The number of cases in the area and in the U.S. is expected to double in the next 13 months.