These bats were accidentally infected with the T-virus during certain outbreaks. The bats slightly grew in size and became much more aggressive. The bats diet now consisted of meat. To hunt for prey the bats would attack in groups, normally targeting humans that would approach them.

There were two reported cases of bats being infected the first at the Umbrella training facility and later on at Rockfort Island. These bats were mere a nuisance for the heroes; even a simple lighter could scare them away.