Rabies From Bats

Human rabies infection is a rare event in the United States. However, post-exposure prophylaxis (PEP) must often be considered for many individuals who have potential exposures to rabies. While only one to three cases of human rabies are typically reported annually, 30,000-60,000 U.S. residents receive PEP and hundreds of thousands of animals are observed or tested for rabies every year.¹ Several recent reports highlight the consequences of missed opportunities for rabies prevention. Also reported recently is a rare instance of the apparent failure of appropriate PEP to prevent rabies infection. 

In July 2020 an 84-year-old man woke from sleep when a bat bit his right hand. After the bat tested positive for rabies three days later, the man was started on PEP including human rabies immunoglobulin (HRIG) and rabies vaccine. He completed the four-dose rabies vaccine series on schedule and as recommended for previously unvaccinated persons. In January 2021, he developed progressive symptoms beginning with painful right-sided facial paroxysms with increased right eye lacrimation, followed by facial paresthesia, and progressing to dysphagia, generalized weakness, and ultimately death.

Rabies viruses sequenced from the patient and the bat were indistinguishable. The investigation following his demise yielded no concerns about the potency of either the rabies vaccine or the HRIG given to the patient but demonstrated no neutralizing antibodies to rabies in the patient’s serum, suggesting a poor response to vaccine, likely (per the authors) due to a previously undiagnosed immunodeficiency. This is the only documented case of rabies PEP failure in humans in the United States when cell-culture vaccines (first introduced in 1978, both current vaccines are made with this technique) have been used. This case illustrates that immunocompromised individuals may need additional post-exposure care (potentially including additional doses of vaccine or even HRIG),² but also serves as a reminder that rabies PEP is typically highly reliable. 

Three additional deaths from rabies occurred in the autumn of 2021, two in adults and one in a child. None of these individuals received rabies PEP and all had significant bat exposures. One individual was aware of the possibility of rabies and submitted the bat for testing, but refused PEP, due to fear of vaccines, even after the bat tested positive for rabies. The other two patients did not recognize their risk. The child knew he was bitten, but rabies PEP was not pursued by his parents because there were no visible bite marks. He had multiple medical visits with escalating symptoms starting with pain in the arm that was bitten. When he presented with hypersalivation and mental status changes he was admitted and intubated. Rabies was suspected based on the history of the bite once that history was elicited by infectious diseases providers. He eventually died on hospital day 16.^3,4 

Bats have been the most common cause of human deaths from rabies in the United States, at least in the past decade plus.^1,4 Contact with bats is typically recognized as bites are painful. However, due to the small, needle-like teeth in some bats, bites do not always leave any visible marks. Contact should generally be assumed in situations where infants, small children, or persons impaired by substances or other causes have been unattended in the presence of a bat.