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Rabies

Rabies virus is an RNA virus that causesthe zoonotic disease, rabies. Rabies virus is transmitted to humans in the saliva of clinically ill mammals by a bite. Rapidly progressive encephalomyelitis typically develops after a 1 to 3-month incubation period. Symptoms include hydrophobia, muscle spasms, and altered mental status. Rabies is almost invariably fatal within 20 days after the onset of encephalomyelitis.

Wild animals are the most important potential source of infection for both humans and domestic animals in the United States. Most reported cases of rabies occur among carnivores, primarily raccoons, skunks, and foxes and various species of bats. Rabies among insectivorous bats occurs throughout the continental United States. For the past several decades, the majority of naturally acquired, indigenous human rabies cases in the United States have resulted from variants of rabies viruses associated with insectivorous bats.

The canine rabies virus variant was eliminated from the United States in 2004 but remains endemic in 122 countries and is the leading global cause of human deaths secondary to zoonotic pathogens. Nine deaths have been reported in the United States from rabies infection acquired while traveling or working abroad since 2008.

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 (https://www.cdc.gov/infectioncontrol/guidelines/isolation/appendix/standard-precautions.html)

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.

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