A Victorian man is reportedly in a essential situation in hospital after contracting Japanese encephalitis from a mosquito chew.
This news comes after each Victoria and New South Wales issued public well being alerts in latest weeks warning in regards to the virus.
So what’s Japanese encephalitis, and how will you defend your self and your loved ones should you reside, work or are holidaying in mosquito-prone areas this summer time?
Relative to different elements of the world, Australia has historically been very low danger for probably life-threatening mosquito-borne ailments.
There’s no widespread dengue, yellow fever or malaria. But there are nonetheless many viruses that native mosquitoes can unfold.
About 5,000 circumstances of mosquito-borne illness are reported in Australia annually. The overwhelming majority of those are because of Ross River virus. The illness this virus causes shouldn’t be deadly, although it may be severely debilitating.
Disease attributable to two different pathogens, Japanese encephalitis virus and Murray Valley encephalitis virus, are a lot rarer however probably deadly.
The signs of human illness attributable to these two viruses are related.
Most individuals contaminated present no signs. In gentle circumstances, there could also be fever, headache and vomiting. In extra critical circumstances, individuals might expertise neck stiffness, disorientation, drowsiness and seizures. Serious sickness can have lifelong neurological issues and, in some circumstances, the illness is life-threatening.
There’s no particular therapy for both illness, although there’s a vaccine for Japanese encephalitis which can be acceptable for sure individuals at excessive danger (extra on that later).
Murray Valley encephalitis virus has been identified in Australia for a lot of many years. After a major outbreak throughout the Murray Darling Basin area in 1974, exercise has typically been restricted to northern Australia.
Outbreaks in southeastern Australia typically accompany flooding introduced on by La Nina climate patterns. Floods present perfect situations for mosquitoes, in addition to the waterbirds that harbour the virus.
Japanese encephalitis virus is carefully associated to Murray Valley encephalitis virus. Mosquitoes choose up each viruses by biting waterbirds. But Japanese encephalitis virus has solely lately change into widespread in Australia.
After flooding rains introduced on by La Nina in 2020, situations that persevered for 3 years, Murray Valley encephalitis virus returned and Japanese encephalitis virus arrived for the primary time.
Japanese encephalitis virus was initially found in southeastern Australia throughout the summer time of 2021-22, and the growth in mosquito and waterbird populations that adopted flooding on the time contributed to its unfold.
There have been round 80 circumstances of illness attributable to these two viruses mixed over the previous 4 years. This contains seven deaths because of Japanese encephalitis throughout Queensland, NSW, South Australia and Victoria.
Additional deaths have been reported because of Murray Valley encephalitis in recent times – two every in Western Australia and the Northern Territory.
In the summer time of 2023-24, scorching and dry summer time situations returned, mosquito numbers declined, and the variety of circumstances of illness attributable to Japanese encephalitis virus and Murray Valley encephalitis dropped.
Now each viruses seem like again. So what is going on on?
This summer time, Japanese encephalitis virus has been detected in mosquitoes and feral pigs in NSW. The virus has additionally been detected in environmental surveillance in northern Victoria, and we all know a minimum of one individual has been affected there.
Meanwhile, Murray Valley encephalitis virus has been detected in sentinel hen flocks – which well being authorities use to check for elevated mosquito-borne illness danger – in NSW and within the Kimberley area of Western Australia.
It’s uncommon to see exercise of those viruses when situations are comparatively dry and mosquito numbers comparatively low.
Some areas of Australia might have skilled flooding, however for a lot of areas of the nation, situations have been scorching and dry. This is unhealthy news for mosquitoes.
There isn’t any proof that mosquito numbers are booming like they did again when La Nina introduced floods to the Murray-Darling Basin.
There additionally is not any proof of extra waterbird exercise. In reality, numbers have declined in recent times.
So why are Japanese encephalitis virus and Murray Valley encephalitis virus lively once more when the situations seem like much less beneficial?
Despite predictions of a uncommon mid-summer return of La Nina, there’s nonetheless hypothesis about what this implies for temperature and rainfall. We might not see flooding, however there may be nonetheless prone to be sufficient water round for mosquitoes.
For Japanese encephalitis virus, it might be that feral pigs are enjoying a extra vital function in its unfold. We know numbers are on the rise and with drier situations, maybe mosquitoes and feral pigs, and different wildlife, are gathering collectively the place they’ll discover our bodies of water.
After its sudden arrival, it now appears Japanese encephalitis virus is right here to remain. But how this virus interacts with native mosquitoes and wildlife, beneath the affect of accelerating unpredictable weather conditions, requires extra analysis.
The public well being alerts in Victoria and NSW focus particularly on particular areas in northern Victoria and round Griffith and Narromine in NSW the place the virus has been detected.
If you reside or work in areas susceptible to Japanese encephalitis, search recommendation out of your native well being authority to see in case you are eligible for vaccination. Residents in specified native authorities areas in affected areas in each states are presently eligible for a free vaccine.
But there isn’t any vaccine out there for Murray Valley encephalitis or Ross River viruses.
Wherever you reside, mosquito chew prevention is vital. Apply insect repellent when outdoor, particularly throughout daybreak and nightfall when mosquitoes are most lively or at any time of the day should you’re in bushland or wetland areas the place numbers of mosquitoes could also be excessive.
You can get higher safety by additionally protecting up with a long-sleeved shirt, lengthy pants, and lined footwear.