Between the Spanish flu, the black death, yellow fever, and polio, I've had a hilarious time reading about epidemics. But nothing compares to Ebola. The Hot Zone by Richard Preston is the actual most disgusting book I have read, this coming from a girl who pretty much only reads about diseases and serial killers.
Funny story - this book was assigned to Dude in junior high. He had horrible nightmares, and his dad ended up calling the school to complain. What kind of monsters would make children read this book? I can't even describe the symptoms here, on a forum for adults, in good conscience. If you want to know, go to Wikipedia - and be prepared.