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South Australians are warned to avoid exposure to mosquitoes, following the recent detection of various flaviviruses and acute encephalitis in southern parts of Australia, which are spread through the bite of an infected mosquito.

The Department for Health and Wellbeing’s Executive Director of Health Protection and Licensing Services, Dr Chris Lease, said the south east of Australia is currently experiencing a La Nina weather pattern, which increases the risk of mosquito-borne diseases, including flavivirus infection.

“In South Australia, there have been seven cases of acute encephalitis identified in the past month, which are currently undergoing investigation for flavivirus infection,” Dr Lease said. “All of these people required hospitalisation with four people currently still in hospital, and one person having passed away.”

“In recent weeks, the Kokobera virus has been detected in adult mosquitoes locally here in the Riverland, and what we have seen so far interstate is detection of the rare Japanese encephalitis virus (JEV) in pigs in New South Wales, Victoria and Queensland, while West Nile virus (Kunjin variant) was detected in horses in New South Wales in January.

“Kokobera virus, Japanese encephalitis virus, West Nile virus, and Murray Valley encephalitis virus all belong to a group of viruses called flaviviruses. Most people who are infected with these viruses are asymptomatic or develop a mild febrile illness, but a small proportion of infected people – less than 1% – will develop encephalitis, which may be fatal or cause long-term neurological damage. Symptoms of encephalitis may include confusion, headaches, neck stiffness, tremors, drowsiness and seizures.

“Japanese encephalitis virus (JEV) is endemic in the Torres Strait and has not previously been detected in New South Wales or Victoria, and has never been detected in South Australia.

“While Murray Valley encephalitis virus (MVEV) and West Nile virus (Kunjin variant) are endemic in birds in northern Australia with occasional cases occurring in humans. MVEV rarely occurs in South Australia, with the last case of MVEV notified in 2011.

Chief Veterinary Officer Dr Mary Carr said the Department of Primary Industries and Regions (PIRSA) is currently undertaking surveillance measures within South Australia to monitor for the JEV disease, and are working closely with interstate counterparts and SA Health.

“The normal lifecycle of JEV is between waterbirds and mosquitoes, which may then accidentally spill over to pigs and horses, but there are currently no confirmed livestock detections of JEV in South Australia.” Dr Carr said.

Dr Lease said, in addition to the seven cases of acute encephalitis, we have also seen an increase in the number of Ross River virus cases.

There have been 77 Ross River cases reported in the State so far this year, compared to 48 cases at the same time last year. This is an even stronger reminder for all South Australians to be vigilant in their fight against mosquito bites.

“To protect against mosquito-borne diseases, we are encouraging people to ‘fight the bite’ and take precautions such as wearing long, loose-fitting, light-coloured clothing and using a repellent which contains DEET or picaridin,” Dr Lease said.

“People should also reduce the risk of being bitten by mosquitoes by proofing their homes and by removing any potential breeding sites on their properties.”

 

Original content from Outbreak News Today and Yale University. Note: Content has been edited for style and length.

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