How many Americans have AIDS?

As of last Monday, 35,980 reported cases. The number is doubling every 12 to 15 months.

Who gets AIDS?

To date, about 70 percent of U.S. cases have been in gay or bisexual men and 20 percent more in intravenous drug users. But anyone exposed to the virus can get AIDS.

How is the virus transmitted?

By sexual contact -- either heterosexual or homosexual -- and by sharing intravenous drug needles or any other exchange of blood or semen. Not by casual, nonsexual contact -- and not by donating blood.

How many of those exposed actually get AIDS?

Between 20 and 30 percent of those who test positive for the virus will come down with AIDS within five years, health officials say. Many expect the percentage to rise with time.

Is it always fatal?

No one is known to have survived a full-blown case of AIDS. More than half die within two years of diagnosis.

What are the prospects for a cure?

Unlikely soon, but as many as a dozen life-prolonging drugs for some people with AIDS are expected by 1991. One, called AZT, already is approved for some patients.

A vaccine?

No "magic bullet" there either, but thousands of researchers are working on it. One of the biggest obstacles is the difficulty of testing a potential vaccine; no other animal responds to the AIDS virus exactly the way humans do.