A rat is a rodent considered to be vermin in most settings as they are often thought to be a vector for the spread of diseases, although in some cases they are domesticated as pets. They also have a historical use in the world of science, as rats and mice are often used in experimentation.
While Infected Rats were found throughout Raccoon City, the large majority of rats are uninfected and behave as they would normally. They have been known to appear in combat areas such as West Africa - and while they are very skittish and harmless, they can still be killed and sometimes they will drop resources.
Their inclusion in the games in their uninfected forms are merely to add ambience to specific areas.
