On March 4, 2022, Australia’s Acting Chief Medical Officer, Dr. Sonya Bennett,declared由于发现新南威尔士州，维多利亚州和昆士兰州的猪的日本脑炎病毒，以及南澳大利亚州可能的人类病例，这是一个具有全国意义的传染病事件。随后关于静止出生和小猪弱的报告in the same provinces in mid-February 2022, and acase acquired in Tiwi Island，，，，Northern Territory in April 2021.

Japanese Encephalitis virus，日本脑炎疾病的病因，是一种正义的单链RNA病毒，在Flaviviridae与其他蚊子传播病毒（例如登革热病毒和西尼罗河病毒）密切相关的家庭，默里河谷脑炎病毒和USUTU病毒是其closest relatives。日本脑炎病毒的大多数感染都是无症状的，但在250种感染中，有1个导致2至26天的孵育期后大脑炎症，头痛，呕吐，发烧，混乱和癫痫发作。有症状病例的死亡率可能高达20％，并具有唯一治疗方法。该病毒在亚洲广泛，每年报告多达70,000例病例。

日本脑炎病毒本身并不是澳大利亚的新颖。除了在旅行者中进口案件外，在外部发现了它托雷斯海峡群岛between Australia and Papua New Guinea since 1995, with the first case on the Australian mainland detected in 1998 inCape York，，，，the northernmost tip of North Queensland. What makes the current situation special is that Japanese Encephalitis virus has never before been found so widespread in Australia, or so far south on the continent.37个人类案件have been confirmed, with 12 additional probable cases, as of April 20, 2022 in the four provinces mentioned above, with 3 unfortunate fatalities. In areas where Japanese Encephalitis is endemic,children are at a higher riskof symptomatic infection. However, that might not be the case in a naïve population such as people in Australia.

To understand the potential causes and the possible implications of this outbreak, it is useful to talk about thetransmission cycle日本脑炎病毒。类似于其他黄素病毒，例如西尼罗河病毒，日本脑炎主要通过Culex蚊子和鸟类充当放大宿主。人类（以及其他动物，例如马和羊驼）偶然被感染，但没有足够的病毒血症来感染蚊子。然而，与西尼罗河病毒不同，日本脑炎病毒在水鸟类（例如苍鹭和白鹭）中复制。此外，猪是日本脑炎病毒的极好的扩增宿主。

在最后两个夏天，La Nina conditions在澳大利亚东部占主导地位。拉尼娜（La Nina）是一种气象现象，中部和东部热带太平洋冷却，导致降雨增加，尤其是在该国东部和北部。这导致了extreme floodingduring summer in February and March of 2022, causing extensive damage. This followed another flood in March 2021 in the same area. Extensive flooding, leading to stagnant water during the summer is relevant for Japanese Encephalitis for two reasons. First, it provides ample breeding sites to competent vectors of the virus, such asCulex annulirostris。Second, it provides habitat for water birds, which can transport Japanese encephalitis over long distances. One hypothesis for the expansion of Japanese Encephalitis along the eastern States of Australia involves the transport of the virus in migrating water birds, with immunologically naïve hatchlings providing sufficient hosts for the virus to establish.

养猪是澳大利亚的主要产业，有240万头猪在4,300个地点保存，该地点在该行业中雇用36,000人。这些小猪中有许多位于东部州，为日本脑炎病毒提供了数百万宿主。幸运的是，该病毒不能在猪肉中传播，因此即使被感染的猪也是安全的。该病毒确实会导致感染猪的生殖衰竭，并导致静止出生，从而导致economic damage给种植者。这就是如何检测到澳大利亚南部的日本脑炎，但这也意味着猪必须在数月前已被感染为怀孕的母猪。猪中这种病毒的检测意味着，在小猪周围工作和生活的人可能会暴露于感染的蚊子并感染日本脑炎病毒。疫苗是可保护猪反对病毒，但尚未在澳大利亚获得许可。也有几个安全有效的vaccines available to protect humans，，，，but their supply is limited. The Australian government is currently establishing a vaccination program for people who work at or reside around piggeries; conduct mosquito surveillance; or work with the virus or mosquitoes in research or diagnostic laboratory setting.

As with many diseases, it is difficult to predict the future course of this Japanese Encephalitis outbreak in eastern and southern Australia. The main question is whether or not Japanese Encephalitis virus will become endemic in local pig, mosquito and water bird populations. In that case, it will return year after year, infecting more people, potentially necessitating a widespread vaccination program. Unfortunately, vaccinating pigs at piggeries will not sufficiently control transmission, partly becauseferal pigs在澳大利亚很常见，不能接种疫苗。Mosquito surveillanceand control will be important to monitor and curb transmission. Community outreach will be crucial to raise awareness of the importance of adequate protection from mosquito bites, especially for children.澳大利亚is one of the most vulnerable regionsin the world to climate change. Warmer oceans increase the amount of moisture in the atmosphere, further increasing the intensity of extreme rainfall, leading to extreme flooding, such as what happened recently in the eastern States.

For this year, the end of the summer brings hopefully an end to this particular outbreak, as the main vector,Culex annulirostrisneeds temperatures above 17.5 C to survive. However, it is an open question if Japanese Encephalitis will re-appear next summer, and even if not, how frequently can it migrate south with the rains and the birds.

如果您想了解有关此特定爆发的更多信息，我强烈建议您观看一项非常有用的网络研讨会@mozziebitesby the Sydney Infectious Disease Institute athttps://www.youtube.com/watch?v=QClM9ibO9b8&list=PLbH_XanGLPbp20v8epptewYzSW4KykXBK&index=2&t=982s