Information for Doctors

Patient history, duration and progression of illness, and laboratory tests for other common etiologies of encephalitis will help determine if rabies should be on the differential diagnosis list for a patient. Patient history is important to identify a possible exposure to rabies and other encephalitides; however, rabies should never be ruled out based solely on the absence of definite exposure history.

Rabies should be considered in patients with signs or symptoms of encephalitis or myelitis, including autonomic instability, dysphagia, hydrophobia, paresis, and paresthesia, particularly if a nonspecific prodrome preceded the onset of these signs by three to four days. Progressive worsening of neurologic signs is characteristic of rabies and should be considered as a positive indicator for rabies.

Laboratory tests to rule out common encephalitides (herpes, enteroviruses, arboviruses) should be performed. Negative results of these tests would increase the likelihood of rabies as the diagnosis. If a patient presents with symptoms similar to the ones described above, but the neurologic status does not change and the illness continues for longer than three weeks, rabies is unlikely as the diagnosis.

Positive Indicators for Rabies

• Nonspecific prodrome prior to onset of neurologic signs
• Neurologic signs consistent with encephalitis or myelitis
  • dysphagia
  • hydrophobia
  • paresis
• Progression of neurologic signs
• Negative test results for other etiologies of encephalitis

Negative Indicators for Rabies

• Improvement or no change in neurologic status
• Illness with ≥ 2 to 3 week duration