Rabies Risk Assessment: Test Your Knowledge

Erin R. Whitehouse, PhD, MPH, RN


August 08, 2019

Editorial Collaboration

Medscape &

After several infectious etiologies were ruled out, antemortem specimens were collected for testing at CDC. Saliva came back positive for rabies virus RNA, and both CSF and serum were positive for rabies neutralizing antibodies (IgG and IgM). The patient died 7 days after intubation. Postmortem testing of brain tissue detected a rabies virus associated with Tadarida brasiliensis bats.

Clinical Signs and Symptoms of Human Rabies

The United States has one to three cases of human rabies per year; therefore, data are limited on the specific clinical picture.[5,6] The prodromal period may include nonspecific symptoms, such as gastrointestinal illness, cardiovascular complications, or muscle aches, and typically lasts only several days before more severe clinical signs develop. Classic signs and symptoms include paresthesia, muscle and joint pain, difficulty swallowing, progressive paralysis, behavior changes, autonomic instability, and hydrophobia. However, there is no "typical" case of human rabies. The clinical course can vary widely.

A review of US cases from 1960 to 2010 suggests that the median time from exposure to symptom onset is 41.5 days but can range from 8 to 701 days, depending on the route of exposure.[6] Generally, more severe exposures, such as bites or scratches on the face or neck, are associated with shorter incubation periods than less severe wounds in the extremities. However, rabies is a progressive encephalitis that will nearly always lead to death if the patient has not received PEP before symptom onset.

Numerous other more common conditions can mimic rabies symptoms. These include other infectious encephalitis (ie, enterovirus, herpes, syphilis), noninfectious/autoimmune disorders (ie, CNS vasculitis, metabolic encephalopathy), or toxicities (ie, strychnine poisoning, delirium tremens).

Human Rabies Diagnosis, Testing, and Treatment

Local and/or state health departments should be notified anytime human rabies is suspected. Prompt notification ensures that healthcare workers, family members, and others who may have been exposed if the case is positive for rabies can be rapidly evaluated. In addition, antemortem testing for rabies—which includes testing of serum, CSF, saliva, and a nuchal skin biopsy for the presence of rabies viral RNA, rabies virus proteins, or antibodies against rabies—can be completed at the CDC only in collaboration with the local or state health department.

There is no effective treatment for rabies infection. PEP may not be recommended after symptoms develop because some evidence suggests that PEP given at that late stage may exacerbate decline of the patient.[1,7]

Infection Control and Prevention Practices

Rabies infection is not spread by blood but transmitted through saliva, respiratory secretions, tears, and nerve tissue. The only documented cases of human-to-human transmission of rabies have occurred owing to organ and tissue transplantation. Rabies infections therefore call for standard infection control precautions and the use of appropriate personal protective equipment for the given activity.[8] For example, mouth, nose, or eye protection is recommended during procedures or patient-care activities that are likely to generate splashes or sprays of body fluids, secretions, or excretions (eg, intubation or suctioning).