Japanese encephalitis virus is now well entrenched in pockets of Australia, where more than one in 10 people are showing evidence of asymptomatic infection, health authorities say.

The serological survey results show there is “absolutely no chance” of eliminating the virus from south-east and southern Australia even though local cases only emerged this year, says arbovirus expert Associate Professor Greg Devine.

NSW Health has tested blood samples from more than 1000 patients in five areas of rural NSW – Griffith, Temora, Corowa, Balranald and Dubbo – finding one in 11 have serological evidence of previous infection.  

This has prompted the state health department to offer vaccination to all residents or workers in 14 local government areas who are aged 50 and older and spend four hours or more outdoors each day.