The new-developments theory has generally been accepted by the media, and will probably stick. What happened was simple. From 1981 to 1982, diagnosed AIDS cases increased 264 percent. From 1982 to 1983, they increased 170 percent, then 103 percent to the next year. By 1986, the epidemic had slowed to a 63-percent increase from the year before.
All epidemics follow a curve which is never linear, never truly exponential.
Even as they grow larger they always grow more slowly, until eventually they level and drop off. Data collected by the CDC and others indicate that HIV had done most of its dirty work by 1985 the year of the first big media scare. Indeed, in some major U.S. cities the incidence of HIV infection had apparently leveled off in homosexual populations by 1982, and in all cities probably by 1984. And so it did. That happens to coincide nicely with the introduction of AZT, to whose prophylactic efficacy Gall credits the downturn.