Last October, the Wyoming Department of Health reported on the “first confirmed human rabies case ever” in the state in a Fremont County woman. At the time, details were lacking, until now.

The Centers for Disease Control and Prevention (CDC) discussed the case in Friday’s Morbidity and Mortality Weekly Report (MMWR).

Lasionycteris noctivagans/NPS
Lasionycteris noctivagans/NPS

A 77-year-old Wyoming woman was admitted to the hospital in Sep. 2015  with a 5-day history of progressive weakness and ataxia after a fall. On examination, she had slurred speech, could not swallow water, and could not stand without assistance. She had a history of mild dementia.

Because of respiratory failure, she was transferred to a referral hospital in Utah, where she developed progressive encephalitis. On day 8 of hospitalization, the patient’s family told clinicians they recalled that, 1 month before admission, the woman had found a bat on her neck upon waking, but had not sought medical care.

The patient’s husband subsequently had contacted county invasive species authorities about the incident, but he was not advised to seek health care for evaluation of his wife’s risk for rabies.

CDC confirmed the patient was infected with a rabies virus variant that was enzootic to the silver-haired bat (Lasionycteris noctivagans). The patient died on October 3.

She was the first Wyoming resident with confirmed rabies virus infection since the state began documenting reportable infectious diseases in 1911.

The patient’s husband and one other family member required postexposure prophylaxis (PEP) because of potential contact with the woman’s saliva through kissing or sharing of food and drinks during the woman’s infectious period.

During recent decades, most domestically acquired human rabies cases have been associated with bat exposures, either by history of bat contact or infection with bat-associated rabies virus variants; however, in the majority of these cases, no bite was reported. Because bat bites can cause limited injury and therefore can be difficult to detect, the Advisory Committee on Immunization Practices recommends that any person with direct bat contact or who might be unaware of bat contact (e.g., awakening with a bat in the room) undergo evaluation for rabies virus exposure

Rabies is an acute viral infection that is transmitted to humans or other mammals usually through the saliva from a bite of an infected animal. It is also rarely contracted through breaks in the skin or contact with mucous membranes. It has been suggested that airborne transmission is possible in caves where there are heavy concentrations of bats.

According to the Control of Communicable Diseases Manual, all mammals are susceptible to rabies. Raccoons, skunks, foxes, bats, dogs, coyotes and cats are the likely suspects. Other animals like otters and ferrets are also high risk. Mammals like rabbits, squirrels, rodents and opossums are rarely infected.

Rabies infected animals can appear very aggressive, attacking for no reason. Some may act very tame. They may look like they are foaming at the mouth or drooling because they cannot swallow their saliva. Sometimes the animal may stagger (this can also be seen in distemper). Not long after this point they will die. Most animals can transmit rabies days before showing symptoms.

Initially, like in many diseases, the symptoms of rabies are non-specific; fever, headache and malaise. This may last several days. At the site of the bite, there may be some pain and discomfort. Symptomsthen progress to more severe: confusion, delirium, abnormal behavior and hallucinations. If it gets this far, the disease is nearly 100% fatal.

Worldwide it is estimated that there are more than 59,000 deaths due to rabies annually. In the US, 1-2 cases are reported each year.

Human rabies is prevented by administration of rabies vaccine and rabies immune globulin.