Vital Signs

Trends in Human Rabies Deaths and Exposures — United States, 1938–2018

Emily G. Pieracci, DVM; Christine M. Pearson; Ryan M. Wallace, DVM; Jesse D. Blanton, DrPH; Erin R. Whitehouse, PhD; Xiaoyue Ma, MPH; Kendra Stauffer, DVM; Richard B. Chipman, MS, MBA; Victoria Olson, PhD

Disclosures

Morbidity and Mortality Weekly Report. 2019;68(23):524-528. 

In This Article

Abstract and Introduction

Abstract

Introduction: Each year, rabies causes approximately 59,000 deaths worldwide, including approximately two deaths in the United States. Before 1960, dogs were a common reservoir of rabies in the United States; however, increasingly, species of wildlife (e.g., bats, raccoons) are the main reservoirs. This report characterizes human rabies deaths, summarizes trends in rabies mortality, and highlights current rabies risks in the United States.

Methods: Rabies trends in the United States during 1938–2018 were analyzed using national rabies surveillance data. Data from the Healthcare Cost and Utilization Project for 2006–2014 were used to estimate the number of postexposure prophylaxis (PEP) visits per 100,000 persons during 2017–2018. The Centers for Medicare & Medicaid Services' average sales price data were used to estimate PEP costs.

Results: From 1960 to 2018, a total of 125 human rabies cases were reported in the United States; 36 (28%) were attributed to dog bites during international travel. Among the 89 infections acquired in the United States, 62 (70%) were attributed to bats. In 2018, approximately 55,000 persons sought PEP after contact with a potentially rabid animal.

Conclusions and Comments: In the United States, wildlife rabies, especially in bats, continues to pose a risk to humans. Travelers also might be exposed to canine rabies in countries where the disease is still present; increased awareness of rabies while traveling abroad is needed. Vaccinating pets, avoiding contact with wildlife, and seeking medical care if one is bitten or scratched by an animal are the most effective ways to prevent rabies. Understanding the need for timely administration of PEP to prevent death is critical.

Introduction

Rabies virus, a Lyssavirus that infects mammals, is transmitted through saliva, most commonly from the bite or scratch of an infected animal. In the United States, several variants, or strains, of rabies virus circulate in animal reservoirs, including raccoons, skunks, foxes, and bats.[1] Rabies virus infection, regardless of the variant or animal reservoir, is fatal in over 99% of cases, making it one of the world's most deadly diseases. There is no treatment once signs or symptoms of the disease begin, and the disease is fatal in humans and animals within 1–2 weeks of symptom onset. Prompt administration of postexposure prophylaxis (PEP), consisting of rabies vaccine and immune globulin, immediately after exposure effectively prevents disease.[1,2]

The elimination of canine rabies virus variant (CRVV) from the United States is one of the most important public health successes of the 20th century. However, globally, approximately 59,000 persons still die from rabies every year; 98% of these cases are caused by CRVV.[3] At the beginning of the 20th century, CRVV was enzootic in the United States, but beginning in 1947, animal vaccination and leash control laws led to improved rabies control nationwide. Canine rabies and associated human rabies cases fell sharply.[4] By the late 1960s, fewer than 500 rabid dogs and three human rabies cases were reported annually.[5]

In the United States, CRVV was eventually eliminated in 2004[6] through use of parenteral and oral rabies vaccines. As the prevalence of CRVV declined, rabies viruses associated with wildlife reservoirs such as skunks, foxes, raccoons, and bats accounted for an increasing proportion of cases in animals and humans in the United States. Wildlife rabies is found in all states except Hawaii.[1] 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.[7] Given the close proximity of raccoons to residents of suburban neighborhoods and trends toward urbanization, human exposures to rabies increased.[8,9]

The use of oral rabies vaccine, composed of vaccine wrapped in a flavored bait, has been successful in controlling westward spread of raccoon rabies.* However, outside oral rabies vaccination zones, raccoon rabies virus variant accounts for nearly 75% of the terrestrial animal rabies cases reported in the United States.[1] In areas where both raccoon and bat rabies occur, human rabies exposures are 600% higher than in areas where only bat rabies occurs.[1,9]

Although domestic animal exposures account for a large portion of human PEP usage, bat rabies virus variants are responsible for most human rabies deaths in the United States.[1] This apparent paradox might be due to several factors, including lack of awareness of the risk of acquiring rabies from bats, or difficulty identifying bat bites and scratches.[10] This analysis highlights current rabies risks in the United States, and assesses the cost and public health impact of rabies control efforts.

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