Peeps by Scott Westerfeld
When Cal arrived in New York City to attend college, he promptly went out to lose his virginity--which he promptly did. Unfortunately, in the process Cal also picked up something else: a parasite which causes all the symptoms (and strengths) of vampirism. Fortunately, he is partially resistant to the bug--so although he is strong, pale, light-sensitive and hungry for meat, he doesn't (immediately) go crazy and start eating people.
Unfortunately, the Night Watch organization which assists and oversees the control of vampires in NYC seems to be hiding some important information from Cal...and the rest of humanity.
Alternating chapters of Cal's story include scientific, graphic, and tremendously icky information about real parasites: toxoplasma gondii, pigeon mites, various lices, screwworms, and many other really yucky bugs that have plagued (literally) humans and animals throughout history.
The "eewwww" factor is high--and it's absolutely fascinating. Highly recommended for readers with a strong stomach, ages 12 and up.