A Victorian man is in critical condition after contracting Japanese encephalitis from a mosquito bite, raising public health concerns in the region. This case follows recent health alerts Victoria and New South Wales issued, warning residents about the virus.
Understanding Japanese Encephalitis
Japanese encephalitis is a potentially fatal mosquito-borne virus. Although Australia has traditionally been low-risk for such diseases compared to other parts of the world, the presence of Japanese encephalitis highlights the importance of preventive measures.
Symptoms range from mild fever and headaches to severe cases involving neurological complications, which can be life-threatening. There is no specific treatment, but a vaccine is available for those at high risk.
History of Japanese Encephalitis in Australia
Japanese encephalitis virus was first detected in southeastern Australia during the summer of 2021-22, spreading rapidly due to a surge in mosquito and waterbird populations following extensive flooding. Over the past four years, there have been around 80 cases linked to Japanese encephalitis and Murray Valley encephalitis, resulting in seven deaths from Japanese encephalitis across Queensland, NSW, South Australia, and Victoria.
Despite declining mosquito numbers and cases during the hot and dry summer of 2023-24, both viruses have reemerged. Additional fatalities from Murray Valley encephalitis have been reported, with two deaths each in Western Australia and the Northern Territory in recent years, highlighting the ongoing risk of these mosquito-borne diseases.
Mosquito-Borne Diseases in Australia
Australia reports around 5,000 mosquito-borne disease cases annually, mostly due to Ross River virus, which is non-fatal but debilitating. Japanese encephalitis and Murray Valley encephalitis are rarer but more severe.
Influence of Weather Patterns
Historically, outbreaks of Murray Valley encephalitis followed La Niña-induced flooding, which creates ideal conditions for mosquitoes and waterbirds that carry these viruses. Japanese encephalitis, closely related to Murray Valley encephalitis, became widespread after similar conditions persisted between 2020 and 2023.
Current Situation and Predictions
Unusually, Japanese encephalitis has been detected despite drier conditions and lower mosquito numbers. The virus has been found in mosquitoes and feral pigs in NSW and northern Victoria. Murray Valley encephalitis has also been detected in sentinel chicken flocks in NSW and Western Australia.
Speculation about a mid-summer return of La Niña and sufficient water bodies might explain the resurgence of these viruses. The role of feral pigs in spreading Japanese encephalitis is also under consideration.
Reducing the Risk
Health authorities in Victoria and NSW are urging residents in affected areas to consider vaccination. Preventing mosquito bites remains crucial across all regions. Using insect repellents, wearing protective clothing, and minimising exposure during peak mosquito activity times are essential steps to reduce the risk of infection.
Residents in high-risk areas should stay updated with local health advisories and take appropriate precautions to safeguard themselves and their families.
