Rabies in the United States, 1938–2018: Bats, Travel and the Cost of Prevention

Rabies is a virus of mammals, carried in saliva and usually passed on by a bite or scratch. Once symptoms begin there is no treatment: the disease kills people and animals within one to two weeks, and it is fatal in over 99% of cases. Yet it can be stopped completely by acting early. Postexposure prophylaxis (PEP) — rabies vaccine plus rabies immune globulin, given promptly after an exposure — prevents the disease.

A 2019 CDC Vital Signs report looked back over 81 years of national rabies surveillance to ask where the risk comes from now.

Rabies cases in humans and domestic animals, United States, 1938–2018 (CDC).

From dogs to wildlife

Early in the 20th century, the dog variant of the virus was entrenched in the United States. Starting in 1947, pet vaccination and leash laws brought it under control, and cases in dogs and people fell steeply. By the late 1960s fewer than 500 rabid dogs and three human cases were reported a year. The dog variant was finally eliminated in 2004 — one of the great public health successes of the 20th century. Worldwide, though, rabies still kills about 59,000 people a year, and 98% of those deaths come from the dog variant.

As dog rabies faded, wildlife took over as the reservoir: raccoons, skunks, foxes and bats. Wildlife rabies now occurs in every state except Hawaii. Since the late 1970s, raccoon rabies has spread along the Eastern Seaboard from Alabama to Maine, the largest animal rabies epidemic in the nation's history. Vaccine baits have held back its westward spread, but outside those vaccination zones the raccoon variant accounts for nearly 75% of rabies cases in land animals. Where raccoon and bat rabies overlap, human exposures are 600% higher than where only bat rabies occurs.

Who got rabies

• 1938–2018: 588 human cases were reported, and the yearly count fell tenfold as dog rabies was eliminated.
• 1960–2018: 125 cases. Of these, 36 (28%) were U.S. residents bitten by dogs while traveling abroad.
• The 89 cases acquired inside the United States included six from organ transplants, and 62 (70%) were caused by bat variants.

Bats are a puzzle: exposures to pets and other domestic animals account for much of the PEP given, yet bats cause most U.S. deaths. The report suggests that people may not realize bats carry the risk, and that bat bites and scratches are hard to spot. Still, 94% of bats sent for testing do not have rabies, so killing bats wholesale is not recommended — and no rabies vaccine is approved for bats.

What prevention costs

• In 2017–2018, an average of 55,000 people a year (range 45,453–66,000) were treated for a possible exposure.
• A course of PEP averages $3,800 (range $1,200–$6,500), not counting hospital care or wound treatment — about $209 million a year in all (range $66 million–$358 million).
• Since 2003 the public health system has handled, each year, about two human rabies deaths, 175 mass bat exposures (more than 10 people exposed to one possibly rabid bat) and one imported rabid dog.
• About 1.06 million dogs enter the country each year; 107,000 (10%) come from countries where dog rabies persists. Since 2015, three rescue dogs adopted from high-risk countries have brought canine rabies in.
• The emergency response work costs an estimated $7.6 million a year (range $2.6 million–$12.9 million).

Public health laboratories and the U.S. Department of Agriculture's Wildlife Services test about 100,000 animals a year, and about 5,000 are positive. Dogs can still catch rabies from wildlife, and keeping at least 70% of dogs vaccinated protects both pets and their owners — a concern as some owners have grown reluctant to vaccinate.

The estimates have limits: PEP data come from emergency departments and may be incomplete, what hospitals actually bill for PEP varies widely, and response costs differ a great deal from state to state.

How to protect yourself

• Stay away from wildlife, especially bats. Bat bites and scratches are small and easy to miss. If a bat was in a room with a sleeping person, a young child, a person with a mental impairment, or someone under the influence of medicine, drugs or alcohol, assume an exposure may have happened and see a doctor urgently — unless the bat can be safely caught and tested.
• Vaccinate your pets.
• Traveling abroad: avoid animals, know how you would get care after a bite or scratch, and carry travel health insurance. People who will work with animals should consider vaccination before the trip — and still need PEP after an exposure. CDC's Travelers' Health pages list recommendations.
• After any bite or scratch, get medical care as soon as possible. Human rabies is 99% fatal, and 100% preventable.

Sources

• Pieracci EG, Pearson CM, Wallace RM, et al. "Vital Signs: Trends in Human Rabies Deaths and Exposures — United States, 1938–2018," MMWR Vol. 68, No. 23, CDC; a work of the United States government in the public domain. The report gives the cost of a rabid-dog importation as $213,833 per event in its results and $218,833 per two years in its table, so neither figure is stated here.