Muukalainen (1984)

When two brothers, Josh and Mike, go to a small southern town for a vacation, they find most of the residents either dead or missing. When Mike himself goes missing, Josh teams up with the local sheriff and an attractive school teacher to find him until Josh discovers that the whole town and most of it's people have been infected by a form of toxic waste, and they have all turned into toxic vampires whom prowl the streets at night for human blood!