More people were stricken with AIDS in 1985 than in all of the earlier six years since the fatal disease was discovered, the federal Centers for Disease Control reported yesterday in a regular update.

Last year the AIDS epidemic claimed 8,406 new victims, bringing the total of reported cases in the United States, as of Jan. 13, to 16,458. The 1985 figures showed an 89 percent increase in new AIDS cases compared with 1984.

Of all AIDS cases to date, 51 percent of the adults and 59 percent of the children have died. The new report shows that, on average, AIDS patients die about 15 months after the disease is diagnosed.

The rate of increase was expected and confirmed forecasts by public health experts. The same experts say the epidemic shows no sign of slowing and that 1986 is virtually certain to witness almost twice as many new AIDS cases as were counted last year.

"It continues to be very bad news, but it comes as no surprise," said Meade Morgan, chief the statistics section at CDC's AIDS program.

Morgan did, however, point to one good sign in the report. The period of time it takes for the number of AIDS cases to double has continued to lengthen slowly. This confirms earlier indications that the disease was not spreading as fast as the earliest statistics indicated.

In 1982, for example, the number of cases was doubling every five months. Through 1983 and 1984 each doubling came after longer and longer intervals. The most recent doubling took 11 months.

The growth in doubling time suggests that when 1985's victims were infected (several years ago, given the long incubation period), the virus was not spreading at an exponential rate. At such a rate, each infected person would transmit the virus to at least two others who would, in turn, infect four others and so on.

Morgan said the increase in doubling time probably reflected the fact that more and more of those in the high-risk groups -- chiefly homosexual males and intravenous drug users -- were already infected. Thus there are fewer and fewer uninfected members of those groups remaining to pick up the virus.

AIDS, or acquired immune deficiency syndrome, is caused by a recently discovered virus that is spread by the transfer of one person's blood, semen or, possibly, saliva into the bloodsteam of another person. The virus is known to have been transmitted by sexual intercourse, both homosexual and heterosexual, and by the sharing of intravenous needles.

The virus multiplies inside certain blood cells that are an essential component of the immune system, killing them in the process. When the number of these cells drops too low, victims are unable to fight off a variety of other cancers and infections, which eventually prove fatal.

The CDC figures show that AIDS is continuing to spread slowly among heterosexuals. About 4.6 percent of cases to date, 768 individuals, involve heterosexuals who are not drug addicts or members of any known risk group. Of these, 182 are known to have had sexual relations with a member of a risk group. The number of heterosexual AIDS patients more than doubled in 1985.

AIDS cases among recipients of blood transfusions continued to grow, more than tripling from 56 in 1984 to 171 in 1985. CDC officials say that because blood centers began testing all donated blood for signs of AIDS infection only last spring, people who received transfusions in earlier years are still at risk.

The number of children with AIDS increased by 175 percent during 1985, from 48 cases in 1984 to 132. Seventy-five percent came from families in which one or both parents have AIDS. Most of the others stem from transfusions.

It is now clear that the virus can remain dormant in the body for at least seven years before becoming active enough to cause AIDS. Many AIDS researchers fear the incubation period could be even longer, probably varying with the individual. As a result, doctors expect to see more cases of AIDS appearing among those who were infected at least as long ago as 1978.

In a related development in Texas, the state health commissioner, Robert Bernstein, yesterday dropped his proposal to quarantine AIDS patients in Texas who refused to stop behavior that could spread the virus.

Bernstein came up with the idea following a Houston incident in which a prostitute with AIDS refused to stop plying her trade on the streets. He said it would be applied only as a last resort if AIDS patients refused to cooperate in protecting others from exposure.

The proposal had been tentatively approved by the Texas Board of Health but it drew such heated criticism from homosexual rights organizations and civil rights groups that Bernstein killed the proposal.

Bernstein said the larger battle against AIDS required a high degree of trust and cooperation between the homosexual community and the health department and that he did not want to jeopardize this by implementing the quarantine regulation.