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Rabies

Rabies virus a Lyssavirus that infects mammals and is transmitted to humans in the saliva of clinically ill mammals by a bite. In the United States, the primary animal reservoirs include raccoons, skunks, foxes and bats. Wildlife rabies is found in all states except Hawaii. Since the late 1970s, raccoon rabies has spread across the Eastern Seaboard from Alabama to Maine, causing the largest epizootic of animal rabies in U.S. history. The use of flavored bait containing oral rabies vaccine has controlled the spread of raccoon rabies.

The canine rabies virus variant was eliminated from the United States in 2004 but remains endemic in 122 countries. Globally, approximately 59,000 people die from rabies every year and 98% of these cases are caused by canine rabies virus.

From 1960 to 2018, a total of 125 human rabies cases were reported in the United States. Thirty-six of these cases (28%) were attributed to dog bites during international travel. Among the 89 infections acquired in the United States, 62 (70%) were attributed to bats. Bats are currently the leading cause of human rabies deaths in the United States. Unlike rabies management programs targeting raccoon, fox, and coyote populations, bat vaccination is not yet logistically feasible.

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 or saliva. 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
  • 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

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