Rabies in Humans
Rabies in Humans
Worldwide: At least 50,000 humans develop rabies each year10. The overwhelming majority of cases occur in areas where dog rabies is common. Most have a history of having been bitten by a dog. In this country, human rabies is very rare; furthermore, most of the recent human rabies infections in the United States have been caused by variants of the rabies virus associated with bats.
U.S.: From 1980 through December 2000, there were 42 human rabies cases reported in the United States3,16,17. Of those, 13 appeared to have been exposed in other countries. Of the remaining 29 people, two were infected with the canine strain of rabies present along the Texas/Mexico border and one was infected by a rabid skunk. The other 26 cases were caused by bat variants of the virus. A definite history of a bat bite was documented for only two of these 26 cases. Twelve of the remaining 24 cases had known contact with a bat.
Airborne transmission: Questions about airborne transmission of rabies are common. Airborne transmission has been demonstrated experimentally in some animal species subjected to prolonged exposures to high concentrations of virus. This means of transmission is of little importance in human rabies. Airborne transmission of rabies was implicated in the deaths of two men who had worked in a Texas cave that harbored millions of bats. Other routes of transmission could not be ruled out in either of these cases, though: one man was noted to have a bleeding scratch after leaving the cave; the other, though gloved, handled numerous bats and had an active case of dermatitis at the time he was exposed4. In addition, two laboratory workers developed rabies after accidental exposures to high concentrations of aerosolized virus, although other routes of exposure could not be ruled out in those cases, either5,6.
Washington state: Eight human rabies cases have been reported in Washington. The first six occurred from 1933-1939. All appeared to have been contracted from rabid dogs. Two recent cases were caused by bat variants of the virus. The first occurred in 1995 in a four-year-old child from Lewis County. A bat found in her bedroom approximately two weeks prior to onset of symptoms later tested positive for rabies [MMWR 1995; 44(34):625-7] The second case was in a 64-year-old man from Mason County who died in January 1997. The case-patient lived in a heavily wooded rural area. He engaged in several outdoor activities, sometimes after dark when bats are active, but had no known exposures to bats or other wild animals in the months prior to his death [MMWR 1997; 46(33):770-3].
Human-to-human transmission: Despite the theoretical risk—and the thousands of human rabies cases worldwide each year—the only documented human-to-human transmission of rabies virus occurred among eight recipients of transplanted corneas obtained from individuals who had died with undiagnosed rabies2. Since that time, more stringent guidelines have been established to prevent similar problems from occurring in the future.
