Rabies

In 2021, the Illinois Department of Health reported the first death from human rabies since 1954. , a man in his 80s woke up to find a bat on his neck. A colony of bats lived on his property, and one had made it into the dwelling. The bat tested positive for rabies, but the man refused to receive the rabies vaccine. He died a few weeks later from the disease. According to the Centers for Disease Control and Prevention (CDC), . CDC further reports that “[t]wenty-five cases of human rabies have been reported in the United States in the past decade (2009-2018). Seven of these infections were acquired outside of the U.S. and its territories.”

Human rabies cases are rare in the United States and other developed countries, because of and animals likely to contact people. .

Human rabies is still a problem in developing nations. According to the World Health Organization (WHO), , with “95% of cases occurring in Africa and Asia.” As WHO reports, most human cases are associated with dog bites, except in Latin America. In Latin America, most cases are associated with bats because of significant advances in dog vaccination. For example, , and sees between 1 and 3 human rabies cases per year, similar to the United States.

In 2022, in the Mexican state of Oaxaca, . The siblings lived in an extremely poor community, where shelter is not secure. By the end of December 2022, two of them had died from the disease, and the third was still being treated in hospital. Rabies infection is almost 100% fatal once symptoms appear without a vaccine. It is nearly 100% non-deadly if a vaccine is given in a timely manner.

Symptoms and Causative Agent

Rabies is a zoonotic disease (one that can be transmitted between animals and humans). The rabies virus is in the Lyssavirus genus, . Scientifically speaking, it is an enveloped RNA virus. As with all viruses, the rabies virus can only replicate by infecting certain cells and multiplying using those cells’ protein-making mechanisms. In humans and other mammals, the cells infected by rabies are nerve cells, with . That replication results in the destruction of the cell. Because nerve cells are difficult to replace, any loss of nerves results in nearly irreversible damage. Once the virus reaches the brain, or damages nerves for vital functions like breathing or heart function, death is all but certain.

Infection with rabies is usually without symptoms for days or weeks, . There are some cases whose incubation is a few days if the amount of virus delivered is high or the person’s immune function is not strong enough. Similarly, there are cases whose incubation is beyond 3 months if the virus is slow to progress from the site of exposure to the nerves and beyond.

According to the Mayo Clinic, : “fever, headache, nausea, vomiting, agitation, anxiety, confusion, hyperactivity, difficulty swallowing, excessive salivation, fear brought on by attempts to drink fluids because of difficulty swallowing water, fear brought on by air blown on the face, hallucinations, insomnia, and partial paralysis.” Once these symptoms begin, death is almost 100% inevitable.

Transmission

Human rabies cases happen when rabid animals bite a person. In rabid animals, the virus travels to the salivary glands and is concentrated there. The neurological symptoms in animals include increased aggression and aggressive reactions to normal encounters. This leads animals to bite, and the virus is then “injected” into a person via the bite wound.

Bites happen through accidental encounters with wildlife (e.g. raccoons or foxes), when unvaccinated domestic animals like dogs and cats encounter wildlife and bite their owners, or when bats enter a human dwelling and bite a person. Bat teeth are extremely sharp, making their bites almost painless. People who find a bat in their dwelling are advised to consult a licensed healthcare professional since some bites may go unnoticed. Only a licensed healthcare provider can assess a person’s risk of rabies after an exposure to an animal bite.

In developing countries, where animal vaccination programs are underfunded or nonexistent, most bites are from dogs in urban settings. In the United States, the natural reservoirs of rabies include bats, foxes, raccoons, and skunks. In Puerto Rico, .

FIGURE 1. Ma, X., Monroe, B. P., Cleaton, J. M., Orciari, L. A., Gigante, C. M., Kirby, J. D., Chipman, R. B., Fehlner-Gardiner, C., Gutiérrez Cedillo, V., Petersen, B. W., Olson, V., & Wallace, R. M. (2020). Public Veterinary Medicine: Public Health: Rabies surveillance in the United States during 2018, Journal of the American Veterinary Medical Association, 256(2), 195-208. Retrieved Dec 31, 2022, from 

Treatment and Care

There is no cure for rabies. Once symptoms begin, medical care involves the management of symptoms. For example, giving fever and pain medication. While there are , these protocols involve advanced medical testing and treatment not usually available in a hospital or medical center, even in a developed country.

For those exposed to an animal bite -- and if there is high suspicion that the animal is rabid -- an initial injection of Human Rabies Immune Globulin (HRIG, antibodies drawn from donor plasma) (e.g. bite). This will get the antibodies in the HRIG working on neutralizing rabies virus, while the person mounts their own immune response. Following the HRIG administration, CDC recommends that a “regimen of four 1-mL doses of HDCV or PCEC vaccines should be administered intramuscularly to previously unvaccinated persons. The first dose of the four-dose course should be administered as soon as possible after exposure. Additional doses should be administered on days 3, 7, and 14 after the first vaccination. For adults, the vaccination should always be administered intramuscularly in the deltoid area (arm). For children, the anterolateral aspect of the thigh is also acceptable. The gluteal area should never be used for rabies vaccine injections because observations suggest administration in this area results in lower neutralizing antibody titers.”

Complications

Without a timely vaccination, rabies progresses to neurological impairment and death. See above for the symptoms.

Available Vaccines

In the United States, the with “human diploid cell vaccine (HDCV) or purified chick embryo cell vaccine (PCECV).” The first dose is to be given as soon as possible after the exposure. The second dose at day three (with vaccination day being day one). The third dose at day seven. And the final dose on day 14. People with immunodeficiency due to illness or medical therapy should consult a healthcare provider, as they may need additional doses of the vaccine to ensure immunity.

In the United States, , RabAvert by Bavarian Nordic and IMOVAX by Sanofi Pasteur. , there are 24 vaccine manufacturers worldwide, producing 27 different products. Most of those manufacturers and their products are found in Asia, and the full impact of the COVID-19 pandemic on the manufacturing and availability of the rabies vaccine is not understood at the end of 2022.

More Information

• “Epidemiology and Burden of Disease” World Health Organization. Available online at:
• “Rabies” Centers for Disease Control and Prevention. Available online at:
• Fooks, A., Cliquet, F., Finke, S. et al. Rabies. Nat Rev Dis Primers 3, 17091 (2017). . Available online at:  
• Subdirección de Rabia y Otras Zoonoses. (SPANISH) Secretaría de Salud de México. Available online at:  
• “Vaccinations for Your Pet” ASPCA.org. Available at: