【解説】インドで流行しているニパウイルスとは

【ニューデリーＡＦＰ＝時事】インドで動物から人に感染する、致死率の高いニパウイルスが流行している。南部ケララ州では先月以来、２人が死亡、他にも３人の感染が確認されている。（写真はインド・コーリコードで、ニパウイルスに感染して亡くなった患者の遺体を移送する医療従事者ら）
　当局は学校を閉鎖し、大規模な検査を実施した。
　ニパウイルスについて分かっていることを以下にまとめた。
　Ｑ：ニパウイルスとは
　Ａ：マレーシアの養豚業者の間で感染症が発生。１９９８年、ニパウイルス感染症と確認された。
　名称は、ウイルスが分離された患者の出身地に由来する。
　流行はまれだが、世界保健機関（ＷＨＯ）はエボラ出血熱、ジカ熱、新型コロナウイルス感染症（ＣＯＶＩＤ－１９）などと並び、ニパウイルス感染症を「優先病原体 （集団発生やパンデミック〈世界的な大流行〉を引き起こす可能性のある病原体） 」リストに掲載している。
　ニパウイルスは通常、動物から人に感染したり、食べ物を介して人に感染したりするが、人から人へと感染することもある。
　ニパウイルスの自然宿主はオオコウモリで、感染源とみられている。
　Ｑ：症状は
　Ａ：急な発熱、嘔吐（おうと）、呼吸器感染など。発作や脳炎を経て昏睡（こんすい）状態に陥る重症例もある。
　ワクチンは開発されていない。
　ＷＨＯによると、致死率は公衆衛生の態勢によって４０％から７５％と幅がある。
　Ｑ：過去の発生事例は
　Ａ：マレーシアで発生した最初の事例では１００人以上が死亡。感染封じ込めのため、１００万頭のブタが殺処分された。
　感染ブタがシンガポールに輸出され、同国の食肉処理場の従業員に感染する事例が１１例発生。１人が死亡した。
　その後はバングラデシュ、インドで主に発生している。両国ともに最初の発生は２００１年。
　バングラデシュでは２００１年以降、１００人超が死亡。インドでも５０人超が死亡している。【翻訳編集ＡＦＰＢＢＮｅｗｓ】
〔ＡＦＰ＝時事〕（2023/09/19-16:44）

Authorities in India are scrambling to contain a rare outbreak of Nipah, a virus spread from animals to humans that causes deadly fever with a high mortality rate.
Here is a look at what we know so far:
- What is the Nipah virus? -
The first Nipah outbreak was recorded in 1998 after the virus spread among pig farmers in Malaysia.
The virus is named after the village where it was discovered.
Outbreaks are rare but Nipah has been listed by the World Health Organization (WHO) -- alongside Ebola, Zika and Covid-19 -- as one of several diseases deserving of priority research for their potential to cause a global epidemic.
Nipah usually spreads to humans from animals or through contaminated food, but it can also be transmitted directly between people.
Fruit bats are the natural carriers of the virus and have been identified as the most likely cause of subsequent outbreaks.
Symptoms include intense fever, vomiting and a respiratory infection, but severe cases can involve seizures and brain inflammation that results in a coma.
There is no vaccine for Nipah.
Patients have a mortality rate of between 40 and 75 percent depending on the public health response to the virus, the WHO says.
- What has happened during previous outbreaks? -
The first Nipah outbreak killed more than 100 people in Malaysia and prompted the culling of one million pigs in an effort to contain the virus.
It also spread to Singapore, with 11 cases and one death among slaughterhouse workers who came into contact with pigs imported from Malaysia.
Since then, the disease has mainly been recorded in Bangladesh and India, with both countries reporting their first outbreaks in 2001.
Bangladesh has borne the brunt in recent years, with more than 100 people dying of Nipah since 2001.
Two early outbreaks in India killed more than 50 people before they were brought under control.
The southern state of Kerala has recorded two deaths from Nipah and four other confirmed cases since last month.
Authorities there have closed some schools and instituted mass testing.
This marks Kerala's fourth recorded spate of Nipah cases in five years. The virus killed 17 people during the first instance in 2018.
The state has managed to stamp out previous outbreaks within a matter of weeks through widespread testing and strict isolation of those in contact with patients.
- Are animal-to-human viruses becoming more frequent? -
Having first appeared thousands of years ago, zoonoses -- diseases that can be transmitted from animals to humans -- have multiplied over the past 20 to 30 years.
The growth of international travel has allowed them to spread more quickly.
By occupying increasingly large areas of the planet, experts say, humans also contribute to disruption of the ecosystem and increase the likelihood of random virus mutations that are transmissible to humans.
Industrial farming increases the risk of pathogens spreading between animals while deforestation heightens contact between wildlife, domestic animals and humans.
By mixing more, species will transmit their viruses more, which will promote the emergence of new diseases potentially transmissible to humans.
Climate change will push many animals to flee their ecosystems for more livable lands, a study published by the scientific journal Nature warned in 2022.
According to estimates published in the journal Science in 2018, there are 1.7 million unknown viruses in mammals and birds, 540,000-850,000 of them with the capacity to infect humans.