You've Got What? Japanese encephalitis virus infection
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This is a viral infection of the human brain caused by the Japanese encephalitis (JE) virus and is a notifiable condition.
Japanese encephalitis (JE) virus is spread to humans through mosquito bites. Most people do not experience any illness, but it can cause a rare and potentially life-threatening infection of the brain.
As part of the national response to the Japanese encephalitis virus (JEV) outbreak, SA Health is offering free Japanese encephalitis virus (JEV) vaccines to groups identified for priority vaccination by the Communicable Diseases Network Australia (CDNA), as well as other vulnerable members of the community.
Vaccines will be distributed to existing Vaccine Distribution Centre providers who have agreed to provide JEV vaccines via the current vaccine distribution pathways. Detailed plans for the delivery of vaccinations will be developed in conjunction with the relevant Local Health Networks, general practitioners and pharmacists.
The initial priority group identified by the CDNA includes people who work at, reside at, or have a planned non-deferable visit to a:
SA Health has expanded the eligibility criteria to reduce risk to the communities with a high risk of exposure to JEV from infected mosquitos.
For information on all eligible groups including proof of eligibility required please see the Japanese encephalitis virus (JEV) vaccine page.
There are two vaccines available in Australia against JEV – Imojev and JEspect.
Imojev is a ‘live’ attenuated vaccine, which means it contains a weakened version of the live virus JEV. Imojev is the recommended vaccine for the 2022/23 JEV Immunisation Program.
JEspect is an inactivated vaccine and is available to those who cannot have the live vaccine.
Anyone aged <5 years or who requires the JEspect will be referred to their GP or the immunisation clinics held by the Alexandrina Council.
Pharmacies will only be administering Imojev and vaccinating people >5 years of age.
ATAGI advises that either Imojev or JEspect can be co-administered with other vaccines if required. For more information see the Australian Immunisation Handbook1.
It is mandatory for medical practitioners, and independent immunisers to report notifiable adverse events following immunisation (AEFI) in South Australia.
The Australian Product Information for JEspect currently states that this vaccine is for use in people aged ≥18 years. ATAGI recommends that children and adolescents aged ≥2 months to <18 years can receive this vaccine. This is based on paediatric studies.10-12 It should also be noted that numerous other regions and countries (e.g. the USA, UK, Europe) have registered and recommended the use of JESpect from 2 months of age. 20-22
Recommended dosages (health.gov.au /health-alerts/japanese-encephalitis-virus-jev/clinical-guidance)
|Imojev||≥9 months||Single dose schedule 0.5 mL subcutaneously (SC)||Pregnancy immunocompromised (live attenuated vaccine). Recent receipt of immunoglobulin or immunoglobulin containing blood products (within last 6-12 weeks). Anaphylaxis to vaccine or component|
|JEspect||2 months to <3 years||2-dose schedule 0.25 mL IM 28 days apart||Anaphylaxis to vaccine or component, including a serious hypersensitivity reaction to protamine sulphate (for JEspect only)|
||≥3 years||2-dose schedule 0.5 mL IM 28 days apart (7 days apart for adults aged ≥18 years if imminent exposure)||None|
A JEV learning resource for health professionals is available online through the NCIRS website.
The normal lifecycle of JE virus is between waterbirds and mosquitoes, which may then transfer over to pigs and horses. Animals and people become infected through the bite of infected mosquitoes.
Mosquitoes involved in the transmission of JE virus are primarily Culex species. The specific species of mosquito implicated in Australia is not yet confirmed.
There is no evidence of transmission from person to person. It cannot be contracted through eating meat products.
Over 90% of JEV infections are asymptomatic.
Acute encephalitis is a serious manifestation and occurs in less than 1% of cases of JEV infection. This is characterised by:
Acute encephalitis has a high case-fatality rate of around 30%. There is no specific treatment. Approximately half of those who survive the acute illness will have neurological sequelae.
JEV infection may also manifest as a milder undifferentiated febrile illness. It sometimes also presents as acute flaccid paralysis or aseptic meningitis.
Information for patients about signs and symptoms can be found on the Japanese encephalitis - including symptoms, treatment and prevention page.
Test for flaviviruses including JEV in persons with suspected encephalitis/meningoencephalitis without identified cause. Send the following:
Routine testing for serology is not recommended prior to vaccination.
Japanese encephalitis is an urgent notifiable condition that must be notified immediately to SA Health if suspected or confirmed by medical practitioners and pathology services by phoning the Immunisation Section on 1300 2332 272 (Monday to Friday between 9.00 am and 5.00 pm).
There is no specific treatment for infection with Japanese encephalitis virus. Serious illness with encephalitis requires management in hospital.