Sources of rabies virus in human infection:
(1) animal (mammal) bite
(2) animal saliva on an open wound or break in the skin
(3) handling an animal (alive or dead) with exposed skin
(4) animal saliva on a mucus membrane
(5) inhalation of aerosolized virus (bat caves, cleaning guano, laboratory work, etc)
(6) corneal or other organ transplantation
(7) handling laboratory specimens or cultures
(8) drinking unpasteurized milk from a rabid cow or goat
Theoretical sources:
(1) eating raw meat or minimally cooked meat
An infected animal may not "rabid" (hypersalivation, biting, etc). The animal may appear perfectly normal or may appear simply disabled (if showing the paralytic form).
The absence of a known exposure is relatively common. Since the interval between exposure and infection can be months or even years, the person may have forgotten the exposure. This underlies the need to consider rabies in any unexplained encephalitis or paralysis.