Japanese Encephalitis Outbreak in South-Eastern Australia, 2022

Abstract

Feedback from operational stakeholders who manage or respond to outbreaks is that they are often too busy to review literature or obtain relevant background information to assist them with acute response. Unlike a traditional analytical outbreak investigation report, Watching Briefs are intended as a rapid resource for public health or other first responders in the field on topical, serious or current outbreaks, and provide a digest of relevant information including key features of an outbreak, comparison with past outbreaks and a literature review. They can be completed by responders to an outbreak, or by anyone interested in or following an outbreak using public or open source data, including news reports.

Japanese Encephalitis Enzootic and Epidemic Risks across Australia

“…JEV epidemic risk is considered possible when competent mosquitoes are present near piggeries, in conjunction with an overlapping distribution with infected reservoirs such as feral pigs and/or waterbirds. Humans working in piggeries or those living near pigs are at the highest risk of JEV spillover [ 5 ]. From our model ( Figure 5 ), southern Queensland, New South Wales, Victoria, South Australia and some parts of Western Australia are at a medium to high risk of JEV spillover into humans.…”

“…Over 40 people were reported to have contracted JEV across the same period with 7 deaths reported to date [ 4 ]. The Australian government initiated a “One Health” approach in response to the JE outbreaks [ 5 ]. The aim of this response was to determine the distribution of JEV, its potential veterinary and anthropogenic risk factors and possible mitigation measures to be instituted [ 6 ].…”

“…Pigs, both domestic and feral, are known to have high rates of infection and play a vital role as amplifying hosts of JEV due to high levels of viremia that can infect mosquitoes [ 22 ] while other mammals are considered dead-end hosts due to insufficient viremia [ 18 , 23 , 24 , 25 ]. Australia has the world’s largest feral pig population, estimated to be between 4 and 24 million animals [ 26 , 27 ] concentrated in the northern tropics of the country [ 5 ]. The fecundity of sows plays a significant role as they generate susceptible populations that can amplify and maintain JEV [ 28 ].…”

Vaccination recommendations for pregnant people travelling overseas

“…8 Recommendations for JEV vaccination in relation to travel may extend to travel within Australia over the coming years with recent identification of cases acquired on the mainland. 13 Yellow fever is a viral illness transmitted by infected mosquitoes with clinical manifestations including hepatic dysfunction, renal failure, central nervous system dysfunction, coagulopathy, and shock. 12 The yellow fever vaccine is a live viral vaccine, which is generally contraindicated in pregnancy except for in extenuating circumstances.…”

“…Clinicians advising pregnant travellers should consider JEV vaccination for shorter‐term travellers if travel is during the wet season, if travel to high risk areas is likely to be repeated, if the person will spend a lot of time outdoors and if the person's accommodation has no air‐conditioning, screens or bed nets 8 . Recommendations for JEV vaccination in relation to travel may extend to travel within Australia over the coming years with recent identification of cases acquired on the mainland 13 …”