Vampires are a hematophagous predatory subspecies of humans created though a flu called l1V1.
Vampires are nearly impossible to tell apart from normal humans most of the time. It's only when they're feeding that their canines grow into fangs and their change. They also start exhibiting animalistic strength and speed, not to mention savagery. Most folklore methods of detecting or warding off vampires are nonsense. Vampires can walk at any time of day or night (although some kinds do tend to burn when exposed to sunlight), reflect in mirrors, have sex (although feeding produces a high much greater than sex), and don't care about religious symbols. The only sure way of dealing with a vampire is shooting him or her in the head or chopping their head off. There are many different types of vampires The type appears to be determined by the person's ethnicity. The world's foremost vampire expert explains that this is due to "junk" DNA that is activated by the virus in some humans, mutating them into their ancestors' idea of a vampire. For example, jiangshi (Chinese hopping vampires) can move by, well, hopping when in vampire state, which works well in a city with lots of roofs to hop between (they also feed on life force). Russian vourdalaks can only feed on their loved ones (or anyone with whom they have a personal connection) and are one of the few types able to pass on their particular mutation to non-Russians. Native American versions have snake-like characteristics. Haitian loup garou are more like werewolves, although they shapeshift only when they wish and are not affected by the moon or outside stress factors. One story reveals that siblings do not necessarily become the same type of vampire (sex could have been a factor here, as the brother is a jiangshi, while the sister is some kind of ogre-like creature, calling herself Hsi-Hsue-Kuei). The US has the most types of vampires popping up than any other country. This is explained by the nature of the US as the "melting pot" of cultures and ethnicities.