Symptoms of Japanese Encephalitis

For Everyone

Key points

  • Japanese encephalitis virus infection can result in febrile illness (fever) or neurologic disease, including meningitis or encephalitis.
  • If you think you or a family member might have Japanese encephalitis, talk to your healthcare provider.
Woman with headache holding both hands to head.

Symptoms

Most people (more than 99%) infected with Japanese encephalitis virus do not have symptoms or have only mild symptoms. In people who develop symptoms of Japanese encephalitis, the time from mosquito bite to feeling sick (incubation period) is typically 5–15 days. Less than 1% of people infected with Japanese encephalitis virus develop neurologic illness.

  • Initial symptoms often include fever, headache, vomiting.
  • Disorientation, weakness, and coma might develop over the next few days.
  • Seizures are common, especially among children.

Treatment

No medicines are available to treat Japanese encephalitis. Rest, fluids, and over-the-counter pain medications may relieve some symptoms.

Outcomes and complications

Among patients who develop encephalitis (inflammation of the brain), about 1 in 4 (20–30%) die.

Although some symptoms improve after the acute illness, 30-50% of patients who develop encephalitis and survive continue to have movement, thinking, or behavioral symptoms.

For Health Care Providers Clinical Features and Diagnosis of Japanese Encephalitis

Testing and diagnosis

See your healthcare provider if you have traveled to an area where Japanese encephalitis virus is present and develop the symptoms described above.

  • Tell your healthcare provider when and where you traveled.
  • Your healthcare provider can order tests to look for Japanese encephalitis virus or other infections that cause similar symptoms.
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Content Source:
National Center for Emerging and Zoonotic Infectious Diseases (NCEZID)