This is called the incubation period of virus. Usually people develop rabies within six months of exposure (e.g. from a bite from an infected animal like a dog or a bat). However, longer incubation periods can occur.his is called the incubation period of virus. Usually people develop rabies within six months of exposure (e.g. from a bite from an infected animal like a dog or a bat). However, longer incubation periods can occur.