Zoonotic spillover can either result in self-limited 'dead-end' infections, in which no further human-human transmission occurs (as with the rabies virus), or in infectious cases, in which the zoonotic pathogen is able to sustain human-human transmission (as with the Ebola virus). If the zoonotic virus is able to maintain successful human-human transmission, an outbreak may occur. Some spillover events can also result in the virus adapting exclusively for human infection (as occurred with the HIV virus), in which case humans become a new reservoir for the pathogen.