Rabies, Animal
2023 Case Definition

Background

Rabies virus infection results in an acute, progressive, and fatal encephalitis in humans and mammals. Although all mammals are susceptible to rabies virus infection, there are multiple species-specific variants of the virus, which have adapted to certain species that serve as viral reservoirs. These species-specific variants are transmitted primarily between members of the same species and, with the exception of bats, occur in geographically distinct regions.¹ The primary reservoir species in the United States (U.S.) are bats (throughout the 49 continental states), raccoons (endemic on the Eastern seaboard), striped skunks (North Central, South Central, Southwest States and California), gray foxes and arctic foxes (Southwest States and Alaska), and mongooses (Puerto Rico).

Laboratory Criteria

Confirmatory laboratory evidence:

• A positive rabies virus direct fluorescent antibody test; OR
• A positive rabies virus direct rapid immunohistochemical test (dRIT); OR
• A positive rabies virus test by immunohistochemistry (IHC) on formalin-fixed tissue; OR
• A positive pan-lyssavirus probe-based real time reverse transcription-polymerase chain reaction RT-PCR test; OR
• Detection of lyssavirus nucleic acid by genomic sequencing; OR
• Isolation of rabies virus (in cell culture or in a laboratory animal).

*While central nervous system (CNS) tissue is most commonly tested and is the preferred tissue type for ruling out a rabies virus or non-rabies lyssavirus infection, identification of rabies virus or a non-rabies lyssavirus in any tissue or body fluid is evidence of infection.

 Note: The categorical labels used here to stratify laboratory evidence are intended to support the standardization of case classifications for public health surveillance. The categorical labels should not be used to interpret the utility or validity of any laboratory test methodology.

Confirmed

Meets confirmatory laboratory evidence.

• Rabies, Animal | 1997 Case Definition