Rabies
Rabies virus an RNA virus in the Lyssavirus genus that infects mammals and is transmitted to humans in the saliva of clinically ill mammals by a bite or scratch. Globally, dog bites are the most common source of rabies infection. In the United States, because most dogs are vaccinated against rabies, the primary animal reservoirs include bats, raccoons, skunks, and foxes. Bats are the leading cause of human rabies deaths in the United States. The use of flavored bait containing oral rabies vaccine has controlled the spread of rabies from raccoons, skunks, and foxes. Wildlife rabies is found in all states except Hawaii.
Cases of human rabies cases in the United States are rare, with only 1 to 3 cases reported annually. Twenty-five cases of human rabies have been reported in the United States in the past decade (2009-2018). Seven of these infections were acquired outside of the U.S. and its territories.
Rapidly progressive encephalomyelitis typically develops after a 1 to 3-month incubation period. Symptoms include hydrophobia, muscle spasms, and altered mental status. There is no treatment once signs or symptoms of the disease begin. Rabies is fatal in 99% of cases within 20 days after the onset of symptoms.
Rabies is preventable if viral exposure is promptly followed by wound cleaning, administration of rabies immune globulin (RIG), and rabies vaccination. Passive administration of RIG provides an immediate supply of virus neutralizing antibodies that has a half-life of approximately 21 days. RIG is intended to provide protective immunity until a patient begins to respond to rabies vaccine. Three cell culture rabies vaccines are licensed in the United States. An active antibody response requires approximately 7 to10 days to develop. Rabies virus neutralizing antibodies generally persist for several years.
CDC recommends using standard precautions when providing care to persons suspected of having clinical rabies, including wearing gowns, goggles, masks, and gloves, particularly during procedures that might result in splashes or sprays from body fluids. Enhanced precautions such as droplet and contact precautions are not considered necessary for prevention of health care–associated rabies virus exposures.
Several laboratory tests are available for detection of rabies virus. Rabies virus antigens can be detected in a skin biopsy by direct fluorescent antibody test. Reverse transcription polymerase chain reaction (RT-PCR) detects viral nucleic acid in skin biopsy, saliva, cerebrospinal fluid, and serum. Rabies virus IgG and IgM antibodies can be detected in serum and cerebrospinal fluid by indirect fluorescent antibody test and rapid fluorescent focus inhibition tests (RFFIT). RFFIT measures the ability of rabies specific antibodies to neutralize rabies virus and prevent the virus from infecting cells.
References
- Noah DL, Drenzek CL, Smith JS, et al. Epidemiology of human rabies in the United States, 1980 to 1996. Ann Intern Med 1998;128:922--30.
- De Serres G, Dallaire F, Côte, Skowronski DM. Bat rabies in the United States and Canada from 1950 through 2007: human cases with and without bat contact. Clin Infect Dis 2008;46:1329--37.
- Pieracci EG, Pearson CM, Wallace RM, et al. Vital Signs: Trends in Human Rabies Deaths and Exposures — United States, 1938–2018. MMWR Morb Mortal Wkly Rep 2019;68:524–528. DOI: http://dx.doi.org/10.15585/mmwr.mm6823e1external icon
- CDC. Recommendations for Application of Standard Precautions for the Care of All Patients in All Healthcare Settings. https://www.cdc.gov/infectioncontrol/guidelines/isolation/appendix/standard-precautions.html
