I wish I'd thought to recommend this book before; it's kind of pertinent:
John Kelly, The Great Mortality: An Intimate History of the Black Death, the Most Devastating Plague of All Time (HarperCollins, 2005).
(Well, maybe not any more, but maybe proportionally it still is.)
The Introduction contains this rather ominous warning (under the circumstances, you might even call it a prophecy):
"In 1995, the year I finished the book, Jonathan Mann, a professor at the Harvard University School of Public Health, warned that AIDS was the beginning of a frightening new era. 'The history of our time will be marked by recurrent eruptions of newly discovered diseases.'"
(It's actually a very good read.)