It's a truth universally acknowledged that good news about epidemics rarely make it into the mainstream media. They like their viruses lethal, their transmission rates soaring, their death rates climbing. That's why you probably won't read the following fact in many other places. In the last year, diagnoses of AIDS in San Francisco plummeted another 60 percent from record lows. Deaths dropped to a new low as well. That doesn't mean that HIV transmission is down - but the signs are good there as well. Nor does it mean that AIDS among the poor and mainly black doesn't remain a huge problem. But what was once the epicenter of the plague has long since ceased to be so. Two cheers.