I remember the plot of the movie involved aliens using human blood for their use.  The aliens would "farm" humans and change their blood.  Individuals would suffer from sweating and fevers, and doctors could not discover the cause of the illness.  Actually, the aliens used drinking water to infect individuals and then take the humans away, only to return them again to earth.  The small town was also closed off as well.   Also, I remember a man, who was infected, jumped into the local drinking water reservoir--- and the alien virus was spread throughout.   One of the humans (female doctor or military person) has flashbacks of having tubes placed into her body sucking out her blood for the aliens.

Unless I am just "dreaming" I think this movie does exist.  Help!