Rabies surveillance in the United States during 2021

Xiaoyue Ma Poxvirus and Rabies Branch, Division of High-Consequence Pathogens and Pathology, National Center for Emerging and Zoonotic Infectious Diseases, CDC, Atlanta, GA

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Sarah Bonaparte Poxvirus and Rabies Branch, Division of High-Consequence Pathogens and Pathology, National Center for Emerging and Zoonotic Infectious Diseases, CDC, Atlanta, GA

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Patrick Corbett Division of Global Migration and Quarantine, National Center for Emerging and Zoonotic Infectious Diseases, CDC, Atlanta, GA

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Lillian A. Orciari Poxvirus and Rabies Branch, Division of High-Consequence Pathogens and Pathology, National Center for Emerging and Zoonotic Infectious Diseases, CDC, Atlanta, GA

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Crystal M. Gigante Poxvirus and Rabies Branch, Division of High-Consequence Pathogens and Pathology, National Center for Emerging and Zoonotic Infectious Diseases, CDC, Atlanta, GA

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Jordona D. Kirby Wildlife Services, APHIS, USDA, Concord, NH

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Richard B. Chipman Wildlife Services, APHIS, USDA, Concord, NH

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Christine Fehlner-Gardiner Centre of Expertise for Rabies, Ottawa Laboratory–Fallowfield, Canadian Food Inspection Agency, Ottawa, ON, Canada

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Cin Thang Centre of Expertise for Rabies, Ottawa Laboratory–Fallowfield, Canadian Food Inspection Agency, Ottawa, ON, Canada

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Veronica Gutiérrez Cedillo Centro Nacional de Programas Preventivos y Control de Enfermedades, Secretaria de Salud de México, CDMX, México

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Nidia Aréchiga-Ceballos Laboratorio de Rabia, Departamento de Virología, Instituto de Diagnóstico y Referencia Epidemiológicos, Secretaría de Salud de México, CDMX, México

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Agam Rao Poxvirus and Rabies Branch, Division of High-Consequence Pathogens and Pathology, National Center for Emerging and Zoonotic Infectious Diseases, CDC, Atlanta, GA

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Ryan M. Wallace Poxvirus and Rabies Branch, Division of High-Consequence Pathogens and Pathology, National Center for Emerging and Zoonotic Infectious Diseases, CDC, Atlanta, GA

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Abstract

OBJECTIVE

To provide epidemiological information on the occurrence of animal and human rabies in the US during 2021 and summaries of 2021 rabies surveillance for Canada and Mexico.

PROCEDURES

State and territorial public health departments and USDA Wildlife Services provided data on animals submitted for rabies testing in 2021. Data were analyzed temporally and geographically to assess trends in domestic animal and wildlife rabies cases.

RESULTS

During 2021, 54 US jurisdictions reported 3,663 rabid animals, representing an 18.2% decrease from the 4,479 cases reported in 2020. Texas (n = 456 [12.4%]), Virginia (297 [8.1%]), Pennsylvania (287 [7.8%]), North Carolina (248 [6.8%]), New York (237 [6.5%]), California (220 [6.0%]), and New Jersey (201 [5.5%]) together accounted for > 50% of all animal rabies cases reported in 2021. Of the total reported rabid animals, 3,352 (91.5%) involved wildlife, with bats (n = 1,241 [33.9%]), raccoons (1,030 [28.1%]), skunks (691 [18.9%]), and foxes (314 [8.6%]) representing the primary hosts confirmed with rabies. Rabid cats (216 [5.9%]), cattle (40 [1.1%]), and dogs (36 [1.0%]) accounted for 94% of rabies cases involving domestic animals in 2021. Five human rabies deaths were reported in 2021.

CLINICAL RELEVANCE

The number of animal rabies cases reported in the US decreased significantly during 2021; this is thought to be due to factors related to the COVID-19 pandemic.

Abstract

OBJECTIVE

To provide epidemiological information on the occurrence of animal and human rabies in the US during 2021 and summaries of 2021 rabies surveillance for Canada and Mexico.

PROCEDURES

State and territorial public health departments and USDA Wildlife Services provided data on animals submitted for rabies testing in 2021. Data were analyzed temporally and geographically to assess trends in domestic animal and wildlife rabies cases.

RESULTS

During 2021, 54 US jurisdictions reported 3,663 rabid animals, representing an 18.2% decrease from the 4,479 cases reported in 2020. Texas (n = 456 [12.4%]), Virginia (297 [8.1%]), Pennsylvania (287 [7.8%]), North Carolina (248 [6.8%]), New York (237 [6.5%]), California (220 [6.0%]), and New Jersey (201 [5.5%]) together accounted for > 50% of all animal rabies cases reported in 2021. Of the total reported rabid animals, 3,352 (91.5%) involved wildlife, with bats (n = 1,241 [33.9%]), raccoons (1,030 [28.1%]), skunks (691 [18.9%]), and foxes (314 [8.6%]) representing the primary hosts confirmed with rabies. Rabid cats (216 [5.9%]), cattle (40 [1.1%]), and dogs (36 [1.0%]) accounted for 94% of rabies cases involving domestic animals in 2021. Five human rabies deaths were reported in 2021.

CLINICAL RELEVANCE

The number of animal rabies cases reported in the US decreased significantly during 2021; this is thought to be due to factors related to the COVID-19 pandemic.

Introduction

The annual rabies surveillance report presents the official statistics for animal rabies in the US, reviews laboratory and epidemiological data from 54 US jurisdictions, and offers an overview of rabies in Canada and Mexico during 2021. In the US, rabies is enzootic in at least 20 species of bats and 4 terrestrial reservoir hosts, including raccoons (Procyon lotor), skunks (primarily Mephitis mephitis [striped skunk]), foxes (Vulpes spp and Urocyon cinereoargenteus), and, exclusively in Puerto Rico, the small Indian mongoose (Herpestes auropunctatus). Rabies virus variants (RVVs) maintained in mesocarnivores have evolved in their respective reservoir host species and circulate in discrete geographic regions of the country (Figure 1).1 While dog-mediated RVVs, the leading cause of human rabies deaths globally, were first eliminated from the US in the 1970s, human exposure to rabies continues to occur from interactions with wildlife and unvaccinated domestic animals.2 Therefore, national surveillance is critical to maintain an understanding of changes in RVV distributions, identify notable events such as translocation of endemic RVVs and host-shift events, and monitor the introduction of nonendemic variants. Delayed recognition of changes to the established rabies epidemiology of the US has the potential to harm public health, animal welfare and production, and wildlife ecosystems throughout the country.

Figure 1
Figure 1

Distribution of major rabies virus variants (RVVs) among mesocarnivores in the US, including Puerto Rico, for 2017 through 2021. Darker shading indicates counties with confirmed animal rabies cases in the past 5 years; lighter shading represents counties bordering enzootic counties without animal rabies cases that did not satisfy criteria for adequate surveillance. Small nonenzootic areas with no rabies cases reported in the past 15 years are shaded if they are in the vicinity of known enzootic counties and do not satisfy criteria for adequate surveillance. ARC FX = Arctic fox RVV. AZ FX = Arizona fox RVV. CA SK = California skunk RVV. ERC = Eastern raccoon RVV. MG = Dog-mongoose RVV. NC SK = North central skunk RVV. SC SK = South central skunk RVV.

Citation: Journal of the American Veterinary Medical Association 261, 7; 10.2460/javma.23.02.0081

Reporting and Analysis

The US National Rabies Surveillance System is a laboratory-based system consisting of approximately 130 public health, agriculture, and academic laboratories that conduct diagnostic animal rabies testing through passive and active surveillance. Fifty-four jurisdictional public health departments conduct accompanying epidemiological investigations. Additionally, the USDA Wildlife Services monitors select geographical ranges to identify the terrestrial distribution of rabies and to monitor the impact of ongoing wildlife rabies management activities.

Human and animal rabies are nationally notifiable conditions in the US; the Council of State and Territorial Epidemiologists defines data elements, case definitions, and timelines for reporting.35 Acceptable diagnostic methods include the direct fluorescent antibody test, direct rapid immunohistochemical test (DRIT), immunohistochemistry, and the LN34 real-time reverse transcription PCR assay (RT-qPCR).6 Both genomic and antigenic typing methods are accepted for rabies virus characterization.7 During 2021, 54 jurisdictions submitted 82,366 animals for rabies testing (24.8 animals submitted/100,000 US human population), of which 80,330 (97.5%) had a conclusive (positive or negative) test result.

Animal rabies cases and viral variant characterization data from 2021 were summarized and compared with historical temporal (Figure 2) and geographic trends by species. The number of rabies cases in 2021 was considered significantly different when outside the 95% CI calculated from rabies cases observed during the preceding 5-year period. Samples that were unsatisfactory for testing or that yielded indeterminate diagnostic test results were excluded from analyses. As rabies epidemiology in the US is well described, positive terrestrial animals and bats without RVV typing data were assumed to have the local terrestrial enzootic RVV or bat-type RVV, respectively.8 However, RVV typing is an important public health priority in supporting RVV surveillance and management.9,10 Criteria for counties to be considered free from terrestrial rabies are described in previous reports and based on an absence of case detection over a 5-year period while maintaining adequate testing levels.1 An overview of rabies surveillance activities in Canada and Mexico during 2021 was provided by the Canadian Food Inspection Agency Centre of Expertise for Rabies and the Centro Nacional de Programas Preventivos y Control de Enfermedades of the Secretaria de Salud (Mexican Ministry of Health), respectively.

Figure 2
Figure 2

Cases of rabies among wildlife in the US, by year and species, 1970 through 2021.

Citation: Journal of the American Veterinary Medical Association 261, 7; 10.2460/javma.23.02.0081

Rabies in Wildlife

During 2021, 3,352 wildlife tested positive for rabies, representing an 18.0% decrease from the 4,090 rabid wildlife reported in 2020 (Table 1). The percentage of rabid wildlife among total tested (8.1%) was significantly lower than the previous 5-year average (9.0%; 95% CI, 8.7% to 9.3%; Supplementary Table S1).

Table 1

Cases of rabies in the US, by location, during 2021.

Location Primary reservoir Total animal cases Domestic animals Wildlife Humans % pos 2021 2020 cases Change (%)
Domestic animals Wildlife Cats Cattle Dogs Horses and donkeys Sheep and goats Other domestic Bats Raccoons Skunks Foxes Other wildlife† Rodents and lago-morphs‡
AK Arctic fox 25 1 24 0 0 1 0 0 0 0 0 0 22 2a 0 0 18.0% 15 66.7%
AL Raccoon 44 6 38 5 0 1 0 0 0 11 24 0 2 1b 0 0 2.5% 51 –13.7%
AR Skunk 24 0 24 0 0 0 0 0 0 9 0 15 0 0 0 0 4.4% 33 –27.3%
AZ Skunk 87 1 86 1 0 0 0 0 0 33 1 34 11 7c 0 0 13.9% 106 –17.9%
CA Skunk 220 0 220 0 0 0 0 0 0 187 0 29 4 0 0 0 4.9% 248 –11.3%
CO Skunk 86 4 82 2 0 0 2 0 0 37 0 43 0 2d 0 0 6.5% 92 –6.5%
CT Raccoon 36 2 34 2 0 0 0 0 0 13 9 4 3 4e 1t 0 4.0% 39 –7.7%
DC Raccoon 8 0 8 0 0 0 0 0 0 1 7 0 0 0 0 0 6.7% 15 –46.7%
DE Raccoon 20 6 14 4 1 1 0 0 0 6 4 2 1 1f 0 0 9.9% 6 233.3%
FL Raccoon 79 9 70 6 0 2 1 0 0 13 40 0 16 1g 0 0 3.8% 81 –2.5%
GA Raccoon 161 16 145 11 1 4 0 0 0 17 67 28 31 2h 0 0 10.6% 189 –14.8%
HI None 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0.0% 0 0.0%
IA Skunk 9 0 9 0 0 0 0 0 0 9 0 0 0 0 0 0 0.8% 12 –25.0%
ID Bat 14 0 14 0 0 0 0 0 0 14 0 0 0 0 0 1 6.2% 17 –17.6%
IL Bat 40 0 40 0 0 0 0 0 0 40 0 0 0 0 0 1 1.3% 38 5.3%
IN Bat 20 0 20 0 0 0 0 0 0 20 0 0 0 0 0 0 1.6% 12 66.7%
KS Skunk 25 2 23 1 1 0 0 0 0 12 0 11 0 0 0 0 2.8% 30 –16.7%
KY Skunk 15 2 13 0 0 2 0 0 0 11 0 2 0 0 0 0 2.2% 17 –11.8%
LA Skunk 1 0 1 0 0 0 0 0 0 1 0 0 0 0 0 0 0.3% 5 –80.0%
MA Raccoon 154 2 152 2 0 0 0 0 0 39 70 34 6 0 3u 0 6.3% 164 –6.1%
MD Raccoon 178 20 158 19 1 0 0 0 0 14 98 13 29 1i 3v 0 5.9% 256 –30.5%
ME Raccoon 67 0 67 0 0 0 0 0 0 16 27 13 11 0 0 0 9.4% 89 –24.7%
MI Skunk 49 1 48 0 0 1 0 0 0 48 0 0 0 0 0 0 1.6% 56 –12.5%
MN Skunk 44 2 42 2 0 0 0 0 0 39 0 3 0 0 0 1 2.3% 40 10.0%
MO Skunk 19 0 19 0 0 0 0 0 0 18 0 1 0 0 0 0 1.1% 16 18.8%
MS Bat 2 0 2 0 0 0 0 0 0 2 0 0 0 0 0 0 0.8% 2 0.0%
MT Skunk 20 2 18 1 0 0 1 0 0 15 0 3 0 0 0 0 4.6% 13 53.8%
NC Raccoon 248 18 230 9 5 3 1 0 0 22 106 60 37 4j 1w 0 7.0% 301 –17.6%
ND Skunk 10 1 9 1 0 0 0 0 0 1 0 8 0 0 0 0 3.2% 13 –23.1%
NE Skunk 30 3 27 1 1 1 0 0 0 26 0 1 0 0 0 0 2.3% 25 20.0%
NH Raccoon 25 2 23 1 1 0 0 0 0 5 13 3 2 0 0 0 4.0% 27 –7.4%
NJ Raccoon 201 11 190 11 0 0 0 0 0 48 103 22 11 2k 4x 0 8.3% 257 –21.8%
NM Skunk 8 0 8 0 0 0 0 0 0 5 0 0 3 0 0 0 2.1% 21 –61.9%
NV Bat 13 0 13 0 0 0 0 0 0 13 0 0 0 0 0 0 4.0% 29 –55.2%
NY Raccoon 237 23 214 20 1 1 1 0 0 71 86 24 27 5l 1y 1 4.6% 346 –31.5%
NYC Raccoon 19 3 16 3 0 0 0 0 0 0 15 1 0 0 0 0 4.7% 38 –50.0%
OH Bat 36 0 36 0 0 0 0 0 0 32 4 0 0 0 0 0 0.9% 40 –10.0%
OK Skunk 34 10 24 4 4 1 1 0 0 4 0 19 0 1m 0 0 5.1% 41 –17.1%
OR Bat 17 0 17 0 0 0 0 0 0 17 0 0 0 0 0 0 5.9% 14 21.4%
PA Raccoon 287 53 234 48 0 1 4 0 0 57 126 26 21 3n 1z 0 5.1% 371 –22.6%
PR Mongoose 22 9 13 1 0 7 1 0 0 0 0 0 0 13o 0 0 22.0% 22 0.0%
RI Raccoon 22 0 22 0 0 0 0 0 0 9 11 1 0 0 1aa 0 3.8% 30 –26.7%
SC Raccoon 101 11 90 7 1 3 0 0 0 21 30 24 14 1p 0 0 7.0% 168 –39.9%
SD Skunk 15 1 14 1 0 0 0 0 0 9 1 4 0 0 0 0 3.1% 10 50.0%
TN Skunk 23 1 22 0 0 1 0 0 0 7 1 13 0 1q 0 0 1.9% 16 43.8%
TX Skunk 456 54 402 28 17 5 3 1 0 164 39 174 24 1r 0 1 5.0% 580 –21.4%
UT Bat 19 0 19 0 0 0 0 0 0 18 0 0 1 0 0 0 6.6% 15 26.7%
VA Raccoon 297 28 269 20 5 1 2 0 0 38 132 56 34 4s 5ab 0 9.4% 351 –15.4%
VT Raccoon 18 4 14 3 1 0 0 0 0 4 4 3 3 0 0 0 2.7% 12 50.0%
WA Bat 12 0 12 0 0 0 0 0 0 12 0 0 0 0 0 0 4.4% 8 50.0%
WI Skunk 29 0 29 0 0 0 0 0 0 29 0 0 0 0 0 0 1.6% 25 16.0%
WV Raccoon 21 2 19 2 0 0 0 0 0 1 12 5 1 0 0 0 2.4% 37 –43.2%
WY Skunk 16 1 15 0 0 0 1 0 0 3 0 12 0 0 0 0 3.3% 40 –60.0%
Total 3,663 311 3,352 216 40 36 18 1 0 1,241 1,030 691 314 56 20 5 4.6% 4,479 –18.2%
2021% 100.0% 8.5% 91.5% 5.9% 1.1% 1.0% 0.5% 0.0% 0.0% 33.9% 28.1% 18.9% 8.6% 1.5% 0.5%
% Pos 2021 4.6% 0.8% 8.1% 1.2% 5.5% 0.2% 3.1% 0.2% 0.0% 5.4% 9.8% 21.7% 20.8% 3.3% 1.2%
Total 2021 4,479 389 4,090 288 43 37 11 9 1 1,400 1,403 846 338 65 38
Change (%) –18.2% –20.1% –18.0% –25.0% –7.0% –2.7% 63.6% –88.9% –100.0% –11.4% –26.6% –18.3% –7.1% –13.8% –47.4%

†Other wildlife includes a2 otters; b1 coyote; c4 bobcats, 1 coati, 1 coyote, and 1 ringtail; d2 others; e2 bobcats and 2 coyotes; f1 deer; g1 opossum; h2 bobcats; i1 coyote; j2 bobcats and 2 coyotes; k2 coyotes; l3 deer and 2 fishers; m1 deer; n2 bobcats and 1 otter; o13 mongooses; p1 otter; q1 tamandua; r1 deer; s2 bobcats and 2 otters.

‡Rodents and lagomorphs include t1 groundhog; u3 groundhogs; v2 beavers and 1 groundhog; w1 beaver; x4 groundhogs; y1 groundhog; z1 groundhog; aa1 groundhog; ab1 beaver and 4 groundhogs.

— = Not applicable. Pos = Positive.

Primary reservoir refers to the most common rabies virus variant in the locality.

Bats

A total of 1,241 bats tested positive in 2021, representing an 11.4% decrease from 1,400 reported in 2020 (Table 1). The percentage of rabid bats among the total tested (5.4%) was significantly lower than the previous 5-year average (6.0%; 95% CI, 5.6% to 6.4%; Supplementary Table S1).

Fifty jurisdictions reported rabid bats during 2021. No rabid bats were reported in Alaska, Hawaii, or Puerto Rico. Bats were the only rabid animals detected in 9 states (Iowa, Idaho, Illinois, Indiana, Mississippi, Nevada, Oregon, Washington, and Wisconsin) in 2021. Over 50% of rabid bats were reported from 8 states: California (187 [15.1%]), Texas (164 [13.2%]), New York (71 [5.7%]), Pennsylvania (57 [4.6%]), Michigan (48 [3.9%]), New Jersey (48 [3.9%]), Illinois (40 [3.2%]), and Minnesota (39 [3.1%]). Rabies virus characterization results were reported for 33.4% of rabid bats. Among bats tested for rabies, 6,679 (28.8%) were described beyond the taxonomic level of order; big brown bats (Eptesicus fuscus; n = 4,579; 4.0% positive) were the most commonly tested, followed by Mexican free-tailed bats (Tadarida brasiliensis; 708; 27.3% positive; Supplementary Table S2).

Raccoons

A total of 1,030 raccoons tested positive for rabies in 2021 (Supplementary Figure S1), representing a 26.6% decrease from 1,403 rabid raccoons reported in 2020 (Table 1). The percentage of rabid raccoons among total tested (9.8%) was significantly lower than the previous 5-year average (11.2%; 95% CI, 10.5% to 11.8%; Supplementary Table S1). The number of raccoon rabies cases peaked in 1993, at 5,912 (Figure 2).11

Twenty states, the District of Columbia, and New York City were enzootic for eastern raccoon (ERC) RVV in 2021, consistent with the past 5 years. These jurisdictions accounted for 96.0% of all rabid raccoons reported in 2021. Rabies virus characterization was conducted on 290 of the 989 (29.3%) rabid raccoons from the ERC RVV area, all of which were confirmed to be infected with ERC RVV (100.0%). The remaining 4.0% (41) of rabid raccoons were reported from states where ERC RVV is not enzootic. South Dakota reported 1 rabid raccoon infected with north central skunk (NCSK) RVV. Texas and Arizona together reported 39 rabid raccoons infected with south central Skunk (SCSK) RVV.

Skunks

A total of 691 skunks tested positive for rabies in 2021 (Supplementary Figure S2), representing an 18.3% decrease from 2020 (846; Table 1). The percentage of rabid skunks among the total tested (21.7%) during 2021 was significantly lower than the previous 5-year average (23.6%; 95% CI, 22.5% to 24.7%; Supplementary Table S1). Over 50% of rabid skunks were reported from 6 states: Texas (174 [25.2%]), North Carolina (60 [8.7%]), Virginia (56 [8.1%]), Colorado (43 [6.2%]), Arizona (34 [5.5%]), and Massachusetts (34 [5.5%]). Rabies virus characterization results were reported for 341 (49.3%) rabid skunks; 193 were infected with SCSK RVV, 106 were infected with ERC RVV, 17 were infected with NCSK RVV, and 25 were infected with bat RVVs (Table 2), of which 14 were reported from Flagstaff, AZ, and infected with a big brown bat RVV during a suspected host shift event.

Table 2

Rabies virus variants identified in domestic and wild animals in the US, including Puerto Rico, during 2021.

Variant Domestic animals Wildlife Total animal cases SEI Non-SEI
Cats Cattle Dogs Horses and donkeys Sheep and goats Other domestic Raccoons Bats Skunks Foxes Other wildlife Rodents and lago-morphs
Arctic fox 0 0 0 0 0 0 0 0 0 12 0 0 12 12 0
Arizona gray fox 1 0 0 0 0 0 0 0 0 10 6 0 17 17 0
Bat 1 0 2 0 0 0 0 415 25 7 2 0 452 425 27
Cosmopolitan dog 0 0 1 0 0 0 0 0 0 0 0 0 1 0 1
Mongoose 0 0 7 0 0 0 0 0 0 0 0 0 7 7 0
North central skunk 3 0 4 1 0 0 1 0 17 0 0 0 26 2 24
Raccoon 47 6 12 2 0 0 290 0 106 64 9 5 541 130 411
South central skunk 29 18 5 3 1 0 39 0 193 25 1 0 314 307 7
Variant reported 81 24 31 6 1 0 330 415 341 118 18 5 1,370 900 470
No variant reported 135 16 5 12 0 0 700 826 350 196 38 15 2,293 863 1,430
Total infected 216 40 36 18 1 0 1,030 1,241 691 314 56 20 3,663 1,763 1,900
Variant typed (%) 37.5% 60.0% 86.1% 33.3% 100.0% 32.0% 33.4% 49.3% 37.6% 32.1% 25.0% 37.4% 51.0% 24.7%
Variant typed 2018–2020
  Mean (%) 32.3% 51.0% 54.5% 50.1% 31.7% 21.7% 23.7% 31.6% 47.0% 40.3% 28.6% 24.5% 33.8% 42.5% 24.7%
  95% CI 26.8%– 44.4%– 51.8%– 33.1%– 18.6%– –4.3%– 20.6%– 26.0%– 43.5%– 29.8%– 18.0%– 17.5%– 30.7%– 38.7%– 21.4%–
37.8% 57.6% 57.2% 67.1% 44.7% 47.6% 26.8% 37.2% 50.4% 50.8% 39.2% 31.4% 36.8% 46.3% 28.1%

*SEI = Samples of epidemiological importance.

Foxes

A total of 314 foxes tested positive for rabies in 2021 (Supplementary Figure S3), representing a 7.1% decrease from 338 reported in 2020 (Table 1). The percentage of rabid foxes among the total tested (20.8%) was significantly higher than the previous 5-year average (18.7%; 95% CI, 17.7% to 19.7%; Supplementary Table S1). Rabies virus characterization results were reported for 118 (37.6%) rabid foxes (Table 2). Sixty-four were infected with ERC RVV, 25 were infected with SCSK RVV, 10 were infected with Arizona fox (AZFX) RVV, 12 were infected with Arctic fox (ARCFX) RVV, and 7 were infected with bat RVVs. No animals were reported infected with the Texas gray fox RVV in 2021; the last animal reported with this RVV was a cow from Texas in 2013.12

Other wild animals

During 2021, reported rabid rodents and lagomorphs included 16 groundhogs (Marmota monax) and 4 beavers (Castor canadensis). Rabies virus characterization results were reported as the ERC RVV for 4 groundhogs and 1 beaver. Other reported rabid wildlife (56) included 14 bobcats (Lynx rufus), 13 mongooses from Puerto Rico, 9 coyotes (Canis latrans), 6 deer (family Cervidae), 6 river otters (Lontra canadensis), 2 fishers (Pekania pennanti), 1 South American coati (Nasua nasua), 1 ringtail (Bassariscus astutus) infected with bat RVV, 1 southern tamandua (Tamandua tetradactyla) infected with ERC RVV,13 and 1 Virginia opossum (Didelphis virginiana) infected with bat RVV (Table 1). Rabies virus characterization was performed on 18 of 56 (32.1%) other wild animals—9 with ERC RVV, 3 with AZFX RVV, 2 with bat RVVs, and 1 with SCSK RVV (Table 2).

Rabies in Domestic Animals

Three-hundred eleven domestic animals tested positive for rabies, representing a 20.1% decrease from the 389 reported in 2020 (Table 1). The percentage of rabid domestic animals among the total tested (0.8%) was not significantly different from the previous 5-year average (0.9%; 95% CI, 0.8% to 0.9%; Supplementary Table S1).

Dogs

A total of 36 dogs tested positive for rabies in 2021, representing a 2.7% decrease from 37 reported in 2020 (Table 1). The percentage of rabid dogs among total tested (0.2%) was similar to the previous 5-year average (0.3%; 95% CI, 0.2% to 0.3%; Supplementary Table S1). Over 50% of rabid dogs were reported from 4 jurisdictions: Puerto Rico (7 [19.4%]), Texas (5 [13.9%]), Georgia (4 [11.1%]), and South Carolina (3 [8.3%]). Rabies virus characterization results were reported for 31 (86.1%) rabid dogs; 12 were infected with the ERC RVV, 7 were infected with the dog-mongoose RVV, 5 were infected with SCSK RVV, 4 were infected with NCSK RVV, 2 were infected with bat RVVs, and 1 dog imported from Azerbaijan was infected with cosmopolitan RVV seen in dogs and foxes in the Caucasus region (Table 2).

Cats

Two-hundred sixteen cats tested positive for rabies in 2021, representing a 25.0% decrease from the 288 reported in 2020 (Table 1). The percentage of rabid cats among total tested (1.2%) was not significantly different from the previous 5-year average (1.3%; 95% CI, 1.1% to 1.4%; Supplementary Table S1). Over 70% of the rabid cats were reported from 7 states: Pennsylvania (48 [22.2%]), Texas (28 [13.0%]), New York (20 [9.3%]), Virginia (20 [9.3%]), Maryland (19 [8.8%]), Georgia (11 [5.1%]), and New Jersey (11 [5.1%]). Rabies virus characterization results were reported for 81 (37.5%) rabid cats; 47 were infected with ERC RVV, 29 were infected with SCSK RVV, 3 were infected with NCSK RVV, 1 was infected with AZFX RVV, and 1 was infected with bat RVV (Table 2).

Other domestic animals

A total of 40 cattle (Bos taurus) tested positive for rabies, representing a 7.0% decrease from the 43 reported in 2020 (Table 1). The percentage of cattle that tested positive for rabies among the total tested (5.5%) was significantly higher than the previous 5-year average (4.2%; 95% CI, 3.4% to 5.1%; Supplementary Table S1). Texas (17 [42.5%]), North Carolina (5 [12.5%]), Virginia (5 [12.5%]), and Oklahoma (4 [10.0%]) together accounted for almost 80% of rabid cattle reported in 2021. Other rabid domestic animals included 17 horses (Equus ferus caballus), 1 mule (Equus spp), and 1 goat (Capra hircus). Rabies virus characterization was performed on 31 of the 59 (52.5%) other domestic animals; 22 were infected with SCSK RVV, 8 were infected with ERC RVV, and 1 was infected with NCSK RVV.

Rabies in Humans

There were 5 US cases of human rabies during 2021 (Table 3); all were fatal.1 Four patients were diagnosed through testing of antemortem samples from Minnesota (Lasionycteris noctivagans [silver-haired bat] RVV), New York (RVV seen in dogs in Philippines), Idaho (L noctivagans [silver-haired bat] RVV), and Texas (Tadarida brasiliensis [Mexican free-tailed bat] RVV). Postmortem samples were sent to the CDC for 3 of these cases for further evaluation. One human rabies case was suspected only after the patient’s death; the diagnosis was made via testing of postmortem samples alone, which were submitted to the CDC from Illinois (L noctivagans [silver-haired bat] RVV).

Table 3

Cases of rabies in humans in the US, including Puerto Rico, by circumstances of exposure and rabies virus variant, January 2000 through December 2021.

Date of onset Date of death Reporting state Age (y) Sex Exposure* Rabies virus variant†
13 Sep 00 20 Sep 00 CA 49 M Contact Bat, Tb
26 Sep 00 9 Oct 00 NY 54 M Bite, Ghana Dog, African
3 Oct 00 10 Oct 00 GA 26 M Contact Bat, Tb
8 Oct 00 25 Oct 00 MN 47 M Contact Bat, Ln/Ps
12 Oct 00 1 Nov 00 WI 69 M Contact Bat, Ln/Ps
19 Jan 01 4 Feb 01 CA 72 M Unknown Dog, Philippines
18 Mar 02 31 Mar 02 CA 28 M Unknown Bat, Tb
21 Aug 02 31 Aug 02 TN 13 M Contact Bat, Ln/Ps
14 Sep 02 28 Sep 02 IA 20 M Unknown Bat, Ln/Ps
10 Feb 03 10 Mar 03 VA 25 M Unknown Raccoon, eastern US
28 May 03 5 Jun 03 PR 64 M Bite, Puerto Rico Dog/mongoose, Caribbean
23 Aug 03 14 Sep 03 CA 66 M Bite Bat, Ln
9 Feb 04 15 Feb 04 FL 41 M Bite, Haiti Dog, Haiti
27 Apr 04 3 May 04 AR 20 M Bite (organ donor) Bat, Tb
25 May 04 31 May 04 OK 53 M Transplant, liver Bat, Tb
27 May 04 21 Jun 04 TX 18 M Transplant, kidney Bat, Tb
29 May 04 9 Jun 04 TX 50 F Transplant, kidney Bat, Tb
2 Jun 04 10 Jun 04 TX 55 F Transplant, artery Bat, Tb
12 Oct 04 Survived WI 15 F Bite Bat, unknown
19 Oct 04 26 Oct 04 CA 22 M Unknown, El Salvador Dog, El Salvador
27 Sep 05 27 Sep 05 MS 10 M Contact Bat, unknown
4 May 06 12 May 06 TX 16 M Contact Bat, Tb
30 Sep 06 2 Nov 06 IN 10 F Bite Bat, Ln
15 Nov 06 14 Dec 06 CA 11 M Bite, Philippines Dog, Philippines
19 Sep 07 20 Oct 07 MN 46 M Bite Bat, unknown
16 Mar 08 18 Mar 08 CA 16 M Bite, Mexico Fox, Tb related
19 Nov 08 30 Nov 08 MO 55 M Bite Bat, Ln
25 Feb 09 Survived TX 17 F Contact Bat, unknown
5 Oct 09 20 Oct 09 IN 43 M Unknown Bat, Ps
20 Oct 09 11 Nov 09 MI 55 M Contact Bat, Ln
23 Oct 09 20 Nov 09 VA 42 M Contact, India Dog, India
2 Aug 10 21 Aug 10 LA 19 M Bite, Mexico Bat, Dr
24 Dec 10 10 Jan 11 WI 70 M Unknown Bat, Ps
30 Apr 11 Survived CA 8 F Unknown Unknown
30 Jun 11 20 Jul 11 NJ 73 F Bite, Haiti Dog, Haiti
14 Aug 11 31 Aug 11 NY 25 M Contact, Afghanistan Dog, Afghanistan
21 Aug 11 1 Sep 11 NC 20 M Bite (organ donor) ‡ Raccoon, eastern US
1 Sep 11 14 Oct 11 MA 40 M Contact, Brazil Dog, Brazil
3 Dec 11 19 Dec 11 SC 46 F Unknown Bat, Tb
22 Dec 11 23 Jan 12 MA 63 M Contact Bat, My sp
6 Jul 12 31 Jul 12 CA 34 M Bite Bat, Tb
31 Jan 13 27 Feb 13 MD 49 M Transplant, kidney Raccoon, eastern US
16 May 13 11 Jun 13 TX 28 M Unknown, Guatemala Dog, Guatemala
12 Sep 14 26 Sep 14 MO 52 M Unknown Bat, Ps
30 Jul 15 24 Aug 15 MA 65 M Bite, Philippines Dog, Philippines
17 Sep 15 3 Oct 15 WY 77 F Contact Bat, Ln
25 Nov 15 1 Dec 15 PR 54 M Bite Dog/mongoose, Puerto Rico
5 May 17 21 May 17 VA 65 F Bite Dog, India
6 Oct 17 21 Oct 17 FL 56 F Bite Bat, Tb
28 Dec 17 14 Jan 18 FL 6 M Bite Bat, Tb
15 Jul 18 23 Aug 18 DE 69 F Unknown Raccoon, eastern US
16 Oct 18 4 Nov 18 UT 55 M Contact Bat, Tb
7 Jan 21 22 Jan 21 MN 84 M Bite § Bat, Ln
11 Feb 21 12 Mar 21 NY 59 M Bite Dog, Philippines
8 Sep 21 20 Sep 21 IL 87 M Contact Bat, Ln
10 Oct 21 28 Oct 21 ID 66 M Contact Bat, Ln
19 Oct 21 10 Nov 21 TX 7 M Bite Bat, Tb

*Data for exposure history are reported when plausible information was reported directly by the patient (if lucid or credible) or when a reliable account of an incident consistent with rabies virus exposure (eg, dog bite) was reported by an independent witness (usually a family member). Exposure histories are categorized as bite, contact but no known bite was acknowledged (eg, waking to find bat on exposed skin), or unknown (eg, no known contact with an animal was elicited during case investigation).

†Rabies virus variants associated with terrestrial animals in the US and Puerto Rico are identified with the names of the reservoir animal (eg, dog or raccoon) followed by the name of the most definitive geographic entity (usually the country) from which the variant has been identified. Rabies virus variants associated with bats are identified with the names of the species of bats in which they have been found to be circulating. Because information regarding the location of the exposure and the identity of the exposing animal is almost always retrospective and much information is frequently unavailable, the location of the exposure and the identity of the animal responsible for the infection are often limited to deduction.

‡Infection was not identified until 2013, when an organ recipient developed rabies.

§The patient had received rabies immune globulin and 4 doses of rabies vaccine.

Dr = Desmodus rotundus. Ln = Lasionycteris noctivagans. My sp = Myotis (species unknown). Ps = Perimyotis subflavus. Tb = Tadarida brasiliensis.

Investigations revealed that 4 of the 5 cases occurred as a result of direct contact with bats; 1 case involved bites from a dog during travel to the Philippines. The association between the exposures and rabies was known to 3 of the affected patients (including the patient bitten by a dog); however, only 1 patient sought rabies postexposure prophylaxis (PEP) before symptom onset. The Minnesota human case is the first known US case of rabies despite timely PEP, which included rabies immunoglobulin and 4 doses of a modern rabies cell culture–derived vaccine; this case was attributed to poor antibody response due to a previously unrecognized immunocompromising condition and is also the first known breakthrough infection after cell culture–derived vaccine in the US. In addition to the testing described above, the CDC performed antemortem (3) and postmortem (1) testing on human samples that were negative for rabies (Illinois, Missouri, Texas, and Kentucky).

During 2022, recommendations of the Advisory Committee on Immunization Practices were published about use of a modified preexposure prophylaxis vaccination schedule to prevent human rabies.14 Among the changes are fewer vaccine doses in the primary preexposure prophylaxis vaccination schedule (including for people who work with live rabies virus in laboratories and those who frequently perform necropsies or handle bats), flexible options for ensuring long-term immunogenicity, less frequent or no antibody titer checks for some lower-risk groups, a new minimum rabies antibody titer that aligns with that of international partners, and clinical guidance about ensuring effective vaccination of immunocompromised persons. The updated recommendations are based on new data and may facilitate improved adherence to Advisory Committee on Immunization Practices recommendations to prevent human rabies.

National Rabies Control Efforts

Primary rabies prevention efforts in the US are led by local and state health departments. Jurisdictions employ preventative measures such as risk communication and public information campaigns, encouraging or requiring pet vaccination (to prevent secondary rabies exposure from wildlife reservoirs); providing animal control services to respond to sick, nuisance, and unwanted animals; providing risk assessments and laboratory diagnosis of animals for residents suspected to have a rabies exposure; and assisting with access to rabies PEP for persons confirmed or suspected to have been exposed to rabies. These programs impact over 4 million bite victims annually and are estimated to prevent more than $1 billion in healthcare-associated costs.15

Rabies management in wildlife populations to prevent the spread and eventually eliminate specific RVVs in mesocarnivores is a collaborative effort led by the USDA Wildlife Services, the Texas Department of State Health Services, other state and local agencies, and the CDC. These landscape-scale programs use oral rabies vaccination (ORV) as the primary rabies control strategy targeting wild mesocarnivore populations. Oral rabies vaccination is used to prevent specific RVVs from gaining a larger geographic footprint, lessen impacts to human and animal health, and reduce the substantial costs associated with rabies prevention and control.

During 2021, the USDA maintained an ORV zone to prevent the spread of ERC RVV in 13 states. The zone was located near the US-Canada border in parts of Maine, New Hampshire, New York, and Vermont. The ORV zone also extended from Lake Erie at the New York-Ohio-Pennsylvania border south through the Appalachia region (ie, Virginia and West Virginia) to the Alabama-Georgia-North Carolina-Tennessee border. An ORV zone in Massachusetts to prevent recurrence of ERC RVV cases on peninsular Cape Cod was also maintained. However, in response to the first case of ERC RVV on peninsular Cape Cod reported since 2013, a coordinated, multiagency contingency response effort occurred, involving trap-vaccinate-release of more than 700 rabies vector species and an emergency ORV baiting effort. No additional rabies cases have been reported on the peninsula to date. Additionally, state and county collaborators conducted ORV programs in local jurisdictional areas of Florida, Maryland, and New Jersey. In total, 9,191,180 baits (vaccinia-rabies glycoprotein recombinant vaccine baits [56%] and adenovirus-rabies glycoprotein recombinant vaccine baits [44%]) were distributed across over 134,000 km2 in the eastern US. Additionally, 1,177,200 baits (vaccinia-rabies glycoprotein recombinant vaccine baits [100%]) were distributed across over 41,000 km2 along the US-Mexico border in Texas to prevent the reintroduction of the canine-coyote RVV into the US.

Rabies in Canada and Mexico

Canada

During 2021, the Canadian Food Inspection Agency received 2,443 samples for rabies testing, of which 2,441 were from animals (6.3 animals tested/100,000 Canada human population).16 There was an 8.7% decrease in the number of animal samples submitted compared with 2020 (2,675), attributable to a decrease in samples, particularly bats, skunks, and raccoons, during July to September 2021. Direct fluorescent antibody testing found 105 (4.3%) animal samples positive, with the majority of cases (78 [74.3%]) detected from June to November. As in past years, the province of Ontario submitted the highest number of samples (1,325 [54.2%]), followed by Alberta (277 [11.3%]), British Columbia (243 [9.9%]), and Saskatchewan (200 [8.2%]). However, the highest rates of case detection were observed in Nunavut (36.4% [4 foxes]), Northwest Territories (NWT; 35.3% [5 foxes and 1 dog]), and the province of Manitoba (17.8% [12 skunks and 9 domestic animals]). Antemortem samples (nuchal skin biopsy, saliva, and CSF) from 2 human suspect cases tested by direct fluorescent antibody and/or RT-qPCR were negative.

Most animal samples were submitted due to potential human exposures (1,777 [72.8%]). A smaller number (479 [19.6%]) were submitted due to contact with domestic animals only, whereas 55 (2.2%) samples had no contact noted on the submission form and 132 (5.4%) were submitted via wildlife surveillance testing programs (either contracted testing [104] or confirmatory testing on samples that were positive or inconclusive in DRIT at other laboratories [28]). Additionally, 10 immunohistochemistry-positive bats were reported to the Canadian Food Inspection Agency but not submitted for confirmatory testing. The largest proportion of rabies cases was found in bat species, (51 [48.6%]), followed by skunks (27 [25.7%]) and foxes (4 arctic foxes and 9 red foxes [12.4%]).

Antigenic variant typing using a discriminatory panel of monoclonal antibodies verified that cases in 2 raccoons from Ontario were typed as ERC RVV; 4 foxes each from both Nunavut and Quebec, and 5 foxes from NWT, were infected with ARCFX RVV; and 12 skunks from Manitoba were infected with NCSK RVV. Cross-species transmission during 2021 was detected in 2 cattle, 1 goat, 1 llama, 2 cats, and 3 dogs from Manitoba infected with NCSK RVV; in 12 rabid skunks in Ontario infected with ERC RVV; and in 1 dog each from NWT and Quebec infected with ARCFX RVV. Two bat-variant viruses associated with big brown bats and silver-haired bats were also detected in skunks from Quebec and British Columbia, respectively.

An outbreak of rabies due to ARCFX RVV first detected in 2020 gained momentum in 2021, increasing from 4 to 15 cases, and has since expanded in size and geographic distribution in 2022, with 38 cases diagnosed in foxes and dogs from NWT, Nunavut, Manitoba, Quebec, and Newfoundland and Labrador. Ontario saw a 56% increase in the number of cases due to ERC RVV (14) from 2020 (9) and detected no cases due to ARCFX RVV, with over 2,800 samples tested by DRIT from the enhanced surveillance zones.17 Similarly, a 61% increase in the number of NCSKV cases (21) from 2020 (13) was observed in Manitoba.

In July 2021, rabies was diagnosed in a dog recently imported from the Middle East. Antigenic typing and N-gene sequencing confirmed the virus variant was one known to circulate in the country of origin.18 This case represents the first known introduction of a canine-variant rabies virus into Canada in over 60 years.

Mexico

In 2021, no reports of dog-mediated human rabies cases were made; the last deaths by this cause occurred in 2005, in the center of the country. No human deaths caused by wildlife-associated virus variants were registered during 2021.

In domestic animals, samples of positive felines were received from the State of Yucatan. The first case corresponded to an adult cat that started showing signs on June 11, with no prior history of vaccination. The detected RVV presented an atypical antigenic pattern, which has been reported to be associated with sylvatic transmission among skunks in Yucatan.19 The second case corresponded to a kitten of 1.5 months old, with signs onset on June 20. This animal caused 3 severe risk contacts; the associated antigenic variant identified was V3, whose reservoir is the hematophagous bat (Desmodus rotundus).

There were no cases of canine rabies in 2021; however, the Institute of Epidemiological Diagnosis and Reference received samples of suspected rabid canines from the states of Nayarit and Morelos, and the samples were determined to be negative. The achievement of maintaining zero dog-mediated human rabies cases and zero canine cases is the result of the National Rabies Program maintaining 2 key strategies: first, the continuity of massive, intensive, and free-of-charge vaccinations in the National Canine and Feline Rabies Vaccination Days, which for the last 10 years have accumulated in average 18 million doses administered to dogs and cats; and, second, the medical and antirabies care given to people attacked by animals susceptible to rabies. In 2021, 3,374 prophylaxis series were initiated out of 49,070 registered aggressions (6.9% initiation rate). Both strategies combined allowed the country to maintain the validation of having eliminated dog-transmitted human rabies as a public health problem, with recognition granted in 2019 by the WHO.

Rabies virus surveillance has been maintained by sending animal samples to the National Network of State Public Health Laboratories and to the Institute of Epidemiological Diagnosis and Reference. The year 2021 saw 12,628 samples processed, with a positivity rate of 0.7%. Species under surveillance during this year included dogs, corresponding to 90.3% (11,404) of the total number of samples sent, while the rest of samples (1,224) corresponded to predominantly cats, bats, skunks, and bovines. From all samples tested, 84 were positive: 2 domestic felines, 67 domestic livestock, and 15 wild animals, including the order Chiroptera.

Discussion

Since the 1940s, the National Rabies Surveillance System has depended on jurisdictional surveillance and reporting of animal rabies testing data to the CDC in accordance with the Council of State and Territorial Epidemiologists’ animal rabies position statement.3 The number of animal samples submitted for rabies testing in 2021 (82,366) was significantly lower than the pre–COVID-19 5-year average (97,828; 95% CI, 94,999 to 100,656). The number of animal rabies cases reported in 2021 (3,663) is also significantly lower than the pre–COVID-19 5-year average (4,903; 95% CI, 4,416 to 5,390). The overall decline in testing in 2021 may be attributed to the impact of the COVID-19 pandemic on human-animal interactions and overextended public health systems. The associated declines in most animal species may also suggest a decline in enzootic rabies transmission in the US.2023

In 2021 and 4 of the past 6 years (2015 through 2018), bats were the most commonly reported rabid animals in the US. Bats were also the source of all 4 US human rabies cases with domestic exposures in 2021. Compared with 2018, fewer rabid bats were identified to genus or species in 2021 (48.2% in 2021; 65.1% in 2018). RVV was determined for only about a third of the rabid bats detected in 2021 (37% in 2018). Improvements in the characterization of bat species and RVV may help inform the geographic distribution of the > 20 different bat RVVs in the US and understand the risk associated with exposures to different bat species. Bat species and RVV identification can both be determined through sequencing-based approaches. The true per-species percent positivity of different bat species is currently not well understood, as the data (Supplementary Table S2) are highly influenced by some jurisdictions reporting species information for positive cases only.

Over 100 countries are considered enzootic for dog-mediated RVVs, which are nearly eliminated from North America. Despite regulations to prevent the reintroduction of canine rabies into North America, at least 10 rabid dogs have been imported over the last 15 years, representing not only a risk of rabies in humans and animals, but also extensive mitigation costs and the potential for reestablishment in domestic animal or wildlife hosts.24 In 2021, 3 dogs that subsequently developed rabies were imported into North America—2 into Canada and 1 into the US, originating from Iran and Azerbaijan, respectively. Both countries are considered to be high risk by the CDC-maintained list “High Risk Countries for Dog Rabies,” which is based on publicly available information on surveillance and control capacities. While nearly all pre-2021 imported rabid dogs resulted from fraudulent paperwork reflecting falsified vaccination records, the 3 imported rabid dogs in 2021 were likely the result of inappropriate administration of, or use of low-quality, rabies vaccines in the country of origin.

Canada is historically free from dog-mediated RVV, the US self-declared elimination of dog-mediated RVVs in 2007, and Mexico has not detected a case of dog-mediated RVV since 2016. Maintaining confidence in these freedom statuses requires viral characterization of every rabid dog. This has proven difficult in the US, with the average viral characterization rate in the previous 5 years reaching only 55%. Improvements in access to characterization capacity for the Puerto Rico Rabies Virus Laboratory through testing at the CDC National Rabies Reference Laboratory and near real-time monitoring of electronic case records to hasten follow-up consultations with affected states have improved characterization rates in 2021, resulting in a significant increase in characterization (86%).

Supplementary Materials

Supplementary materials are posted online at the journal website: avmajournals.avma.org

Acknowledgments

The authors declare that there were no conflicts of interest.

Use of trade names and commercial sources is for identification only and does not imply endorsement by the US Department of Health and Human Services. The findings and conclusions in this report are those of the authors and do not necessarily represent the views of the CDC.

The authors thank the state and territorial public health and agriculture departments and laboratories for their contributions of rabies surveillance data and human case investigations. The authors also thank Rene Edgar Condori, Yu Li, Pamela Yager, Subbian Satheshkumar Panayampalli, Brett Petersen, and other staff of the CDC Poxvirus and Rabies Branch for their help and support.

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  • Figure 1

    Distribution of major rabies virus variants (RVVs) among mesocarnivores in the US, including Puerto Rico, for 2017 through 2021. Darker shading indicates counties with confirmed animal rabies cases in the past 5 years; lighter shading represents counties bordering enzootic counties without animal rabies cases that did not satisfy criteria for adequate surveillance. Small nonenzootic areas with no rabies cases reported in the past 15 years are shaded if they are in the vicinity of known enzootic counties and do not satisfy criteria for adequate surveillance. ARC FX = Arctic fox RVV. AZ FX = Arizona fox RVV. CA SK = California skunk RVV. ERC = Eastern raccoon RVV. MG = Dog-mongoose RVV. NC SK = North central skunk RVV. SC SK = South central skunk RVV.

  • Figure 2

    Cases of rabies among wildlife in the US, by year and species, 1970 through 2021.

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    Pieracci EG, Chipman RB, Morgan CN, et al. Evaluation of rabies virus characterization to enhance early detection of important rabies epizootic events in the United States. J Am Vet Med Assoc. 2020;256(1):6676. doi:10.2460/javma.256.1.66

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    Pieracci EG, Brown JA, Bergman DL, et al. Evaluation of species identification and rabies virus characterization among bat rabies cases in the United States. J Am Vet Med Assoc. 2020;256(1):7784. doi:10.2460/javma.256.1.77

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