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[追加 2011-01-15 14:05]
オーストラリアでは、日本脳炎ウイルスグループの Murray Valley encephalitis virus マレーバレー脳炎ウイルス による感染症の流行は 1917年から計7回。宿主[鳥] – ベクター[主にイエカ属種]。 感染者 1千人あたり 1人発症し、死亡率 25%, 神経学的後遺症 25-50%。同国南東部での発生は 北部・中部での豪雨・洪水の後にみられる。
オーストラリア北部 (Western Australia [西オーストラリア州] および the top end of the Northern Territories [ノーザンテリトリー/北部準州 トップエンド])で風土病。
Twitter http://twitter.com/TweetMedmail/status/26140182080131073

[以下は初回投稿]
オーストラリア南東の内陸部
2つの河川 (Murray, Darling)による Murray-Darling basin マレー ダーリング流域
で、1917, 1918, 1925, 1951年の1月から3月にかけて、脳炎が流行した。

Flaviviridae フラビウイルス科 Flavivirus フラビウイルス属で、日本脳炎ウイルスグループ内 Alfuy virus 近縁の Murray Valley encephalitis virus MVEV マレーバレー脳炎ウイルスによる。

[*] 前の年の11月に洪水を起こすに十分な降雨過多があった。

Am J Public Health Nations Health. 1952 December; 42(12): 1519–1521.
Frank MacFarlane Burnet
Murray Valley Encephalitis
URL http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1526305/

約 50%の死亡率の重症脳炎が、成人よりも小児によく見られた。
1951年、人口 約20 000人の地域で 12人の患者発症。血清学的検査では 1地区の成人の30%が陽性であった。

[*] In the year preceding each of the epidemic years 1917, 1918, 1925, 1951, there was abnormally high rainfall in Western New South Wales in the winter (May-July) and a heavy excess of early summer rainfall in November over the headwaters [源流/上流] of the Darling. The latter seems to be the most important factor.
Since 1913 a November excess sufficient to produce flooding has occurred in onlyfive years, 1916, 1917, 1924, 1933, 1950. All except 1933 were followed by outbreaks of encephalitis in the area we are considering.

カ科イエカ属の 1種 Culex annulirostris を主なベクターとする。
自然宿主は 水鳥などの鳥類 ( bird-mosquito-bird cycle)。
ヒトからヒトに伝染しない。
Wikipedia URL http://en.wikipedia.org/wiki/Murray_Valley_encephalitis_virus

The first epidemics of MVE occurred in 1917 and 1918 in Southeastern Australia following years of high rainfall. The virus was isolated from human samples in 1951 during an epidemic in the Murray Valley, Australia.

Murray Valley encephalitis ProMED検索 期間 1994年1月-2011年1月

Murray Valley encephalitis – Australia (02): (NT) not 20100424.1320
Kunjin/Murray Valley encephalitis viruses – Australia: taxonomy 20100417.1251

[Mod. CP氏解説:
In the 8th ICTV Report Kunjin virus and West Nile virus are grouped together (as members of the West Nile virus species), whereas Murray Valley encephalitis virus is considered to be close to Alfuy virus (together forming the Murray Valley encephalitis virus species). Both species are members of the Japanese encephalitis virus group of flaviviruses. ]

Murray Valley encephalitis – Australia: (NT) 20100416.1227
「激しい頭痛、高熱、傾眠、痙攣が、特に幼ない子どもにみられる。治療を行っても、患者の 25%は死亡し、少なくとも 25% [の症例で] 神経学的影響が残るであろう。…」

Murray Valley encephalitis – Australia (07): (NT) 20090528.1986
Murray Valley encephalitis – Australia (06): (NT) 20090520.1892
Murray Valley encephalitis – Australia (05): (WA) 20090518.1857
Murray Valley encephalitis – Australia (04): (NT) fatality 20090325.1165

[Mod. CP氏解説:
Murray Valley encephalitis virus (MVEV) is endemic in northern Australia (Western Australia [西オーストラリア州] and the top end of the Northern Territories [ノーザンテリトリー/北部準州 トップエンド]).
In northern Australia sporadic cases or small outbreaks of MVE occur every few years, usually during the wet season.
There have been 7 major outbreaks of MVE in Australia since 1917. The last was in 1974 when 58 cases were reported from all mainland states. Since 1974 nearly all cases of MVE have occurred in the north of Western Australia and the Northern Territory, with occasional cases in Queensland, central Australia, and central regions of Western Australia. Serological studies show that only 1 in 800-1000 people infected developed clinical disease. Of those that did, 25 percent have died and a further 25-50 percent have been left with permanent neurological damage.
MVEV activity occurs only occasionally in south-eastern Australia, usually after heavy rains and flooding in northern and central Australia, and it is likely that these epidemics have also resulted from reintroduction of the virus.]

Murray Valley encephalitis – Australia (03): (WA), background 20090316.1066
Murray Valley encephalitis – Australia (02): (WA) 20090314.1055
Murray Valley encephalitis – Australia: (WA), alert 20090306.0936
Murray Valley encephalitis – Australia (NT): alert 20040421.1109
Murray Valley encephalitis – Australia (NT): Confirmed 20010308.0481
Murray Valley encephalitis – Australia (South) 20000427.0635
Murray Valley encephalitis – Australia (W.A.) 19980419.0726