The Coming Plague (1994)
This is a daunting book, just for its sheer size, but keep in mind that the last hundred and some pages are all footnotes. Once you can get past that, this is a fantastic book, although I found some chapters much more readable than others.
The chapters on the hemorragic viruses (Ebola, Marburg, etc) are excellent, the whole book is well written, but she does, for my tastes, go into a bit much detail about the politics of the public health system, especially as it involves AIDS and HIV.
Yes, it is important to know that foot dragging and unreasonable people are part of the reason that we have AIDS epidemics in some areas, but I think she over does it a bit. But this book is well worth reading even still.
Laurie Garrett's website