Australia Reports an Outbreak of Japanese Encephalitis

Japanese Encephalitis
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As a result of the outbreak, Australia has declared the Japanese encephalitis virus a Communicable Disease Incident of National Significance.

In early March, health authorities in Australia informed the World Health Organization (WHO) of three laboratory-confirmed cases of Japanese encephalitis virus (JEV). As of 4th May, a total of 38 human JEV cases have occurred in the country. Out of these, 26 are confirmed cases with definitive laboratory evidence while the rest are probable cases. Cases have come forward from Queensland, New South Wales, South Australia, and Victoria. Moreover, the Department of Health has reported four deaths from the outbreak so far.

These are also the first known locally-acquired detections of JE in humans in these states of Australia and the first detections in mainland Australia since a single case was detected in 1998 in Cape York, Queensland.

World Health Organization

Prior to the outbreak, Australia had only reported 15 Japanese encephalitis cases in over ten years. Thus, demonstrating an unusually high rate of infection. In the past, the virus has shown up in Australia’s Torres Strait Islands, the tip of Cape York and the Tiwi Islands. However, this is mainland Australia’s first locally acquired case since 1998. Furthermore, researchers had previously identified the virus in more than 20 commercial pig farms across New South Wales, Queensland and Victoria, and South Australia.

The WHO are conducting human, animal and environmental investigations to further understand the viral transmission in Australia and assess the risk of disease. Australian authorities are also working closely with affected industries to better control the outbreak. Moreover, the Australian government has declared the outbreak a Communicable Disease Incident of National Significance under the Emergency Response Plan for Communicable Disease Incidents of National Significance.

Can Vaccines Stop the Disease?

As the name suggests, the disease first occurred in Japan in 1871. However, widespread immunization efforts have now made the disease rare in the country. According to WHO, the Japanese encephalitis virus causes more than 68,000 annual cases in parts of Asia. It was also linked to a recent mysterious fever outbreak in India. The mosquito-borne virus belongs to the same family of viruses that causes dengue and yellow fever. Animals such as pigs and water birds can also become infected and serve as hosts for the virus. Humans contract the disease through the bite of infected mosquitoes of the Culex species. However, human-to-human transmission does not occur, nor can humans become infected from consuming meat from infected animals.

Although the majority of infections are asymptomatic, 1 in 250 cases can result in encephalitis, or inflammation of the brain. Moreover, 30-50% of encephalitis cases develop permanent neurologic or psychiatric problems. Signs and symptoms of the disease include fever, headache, neck rigidity, rigors, and malaise. As the infection worsens, people can also develop seizures, spastic paralysis, disorientation, coma, and eventually death. The fatality rate for symptomatic cases is up to 30%.

Currently, there are no treatments for the disease; care is mostly supportive and aimed at stabilizing the patients. Therefore, health experts focus their efforts on preventing the disease. One such intervention is the Japanese encephalitis vaccine, a safe and effective tool for controlling the spread of the disease.

There are two JE vaccines for humans registered for use in Australia only advised for risk groups.

World Health Organization

Australian health authorities aim to administer the vaccine to high-risk groups such as pig farm workers and veterinarians in the affected regions. Moreover, the country is also implementing vector control strategies to remove vector breeding sites and reduce exposure.

Is Climate Change to Blame for the Outbreak in Australia?

According to the US Centers for Disease Control and Prevention (CDC), Japanese encephalitis mostly occurs in Asia and parts of the western Pacific. So, how did the virus make its way all the way to mainland Australia? Several experts believe climate change is to blame.

Recently, eastern parts of Australia received unusually heavy rainfall that caused severe flooding in some regions. Thus, resulting in wetlands that attracted flocks of migratory birds to the area. According to Professor Roy Hall at the University of Queensland in Brisbane, these birds often follow flooded watercourses. Experts believe that the birds may have carried the virus into Australia. Furthermore, Australia’s recent warm and wet weather has also led to an increase in the mosquito population. These mosquitoes likely contracted the virus from feeding on the birds and then later passed the virus to pigs across farms in Australia. However, it remains unclear whether the pigs played a part in the spread of the disease.

WHO recommends increased public awareness of JEV in the affected states and the implementation of activities to remove potential mosquito breeding sites, reduce vector populations and minimize individual exposures, including vector control strategies targeting both the immature and adult stages of the mosquito.

World Health Organization

Along with immunizations and vector control strategies, the WHO is advising people to protect themselves against mosquito bites. The measures include wearing long-sleeved shirts outdoors, using mosquito repellents and avoiding the outdoors during evening and night when the Culex species are most active.

According to the WHO, the risk at both regional and global levels is low. Moreover, since the disease does not spread from person-to-person, the risk of an international outbreak is also low. However, the recent climate change can lead to an increase in mosquito-borne viruses across the world.


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