Public health priority: Urgent.
PHU response time: Respond to confirmed cases within a day of notification. Enter confirmed cases on NCIMS within one working day.
Case management: Determine possible exposures.
Contact management: Nil
A confirmed case requires:
Confirmation of laboratory result by a second arbovirus reference laboratory is required if the case appears to have been acquired in Australia.
A clinically compatible febrile illness of variable severity associated with neurological symptoms ranging from headache to meningitis or encephalitis. Symptoms may include headache, fever, meningeal signs, stupor, disorientation, coma, tremors, generalised paresis, hypertonia, and loss of coordination. The encephalitis cannot be distinguished clinically from other central nervous system infections.
Japanese encephalitis (JE) cases are to be notified by laboratories on diagnosis (ideal reporting by telephone within 1 hour of diagnosis). Only confirmed cases should be entered onto NCIMS.
Japanese encephalitis is one of the arboviruses (arthropod borne viruses known to be pathogenic for humans). The Japanese encephalitis virus is a member of the genus Flavivirus, in the family Flaviviridae (Dengue fever, Murray Valley Encephalitis, Kunjin, Kokobera, Stratford, Alfuy and Edge Hill are also flaviviruses).
JE is transmitted by the bite of an infected mosquito, primarily Culex species. The virus is maintained in cycle between mosquitoes and amplifying vertebrate hosts, primarily pigs and wading birds. Humans are incidental or dead-end hosts, because they usually do not develop a level or duration of viremia sufficient to infect mosquitoes.
There is no evidence of direct person-to-person spread.
The incubation period ranges from 5 to 15 days.
Less than 1% of people infected with JE experience clinical disease. Symptoms are variable, but typically include fever, anorexia and headache. Vomiting, nausea, diarrhoea, muscle aches and dizziness may also occur. More severe infections may cause neurological dysfunction with photophobia, lethargy, irritability, drowsiness, neck stiffness, confusion, ataxia, aphasia, intention tremor, convulsions, coma and death. Seizures are common in children.
The case-fatality rate is approximately 20%-30%. Among survivors, 30%-50% have significant neurologic, cognitive, or psychiatric sequelae.
The clinical presentation for JE is similar to that of Murray Valley Encephalitis (MVE) and Kunjin virus.
Japanese Encephalitis has never been present in NSW. The first Australian-acquired cases were detected in Torres Straits Islander people in 1995.
On same day of notification of a confirmed case begin follow-up investigation and notify the CDB of the case details
Within one working day of notification enter confirmed JE cases on NCIMS
The response to a notification will normally be carried out in collaboration with the case's health carers. But regardless of who does the follow-up, PHU staff should ensure that action has been taken to:
Supportive treatment only.
The case or relevant care-giver should be informed about the nature of the infection and the mode of transmission.
The case should be asked to recall if, in the incubation period, he or she had:
Potentially exposed people are those who may have been exposed to the same source as the case. However, active searching for these people is not usually indicated.
A vaccine is available but is only recommended for travellers spending =1 month in rural areas in countries where the disease is endemic or in some of the Torres Strait Islands.
Educate the public living in or travelling to endemic areas to minimise exposure to mosquito bites. Information should indicate geographical location of habitats, and periods of maximum mosquito activity and also refer to protective clothing, appropriate repellents and methods of reducing mosquitoes in the home. Factsheets are available.