Researchers hypothesize that this vaccine was the source of the virus found in mesotheliomas decades later.

研究人员推测，这种疫苗就是几十年后在间皮瘤中发现的病毒的来源。

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The source of the virus remains unclear, but some suspect it comes from camels.

虽然MERS病毒的来源尚不完全清楚，但是，一些研究怀疑骆驼是来源之一。

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Infected nervous tissue or salivary gland tissue is the best source of the virus.

感染的神经组织或涎腺组织是病毒的最好来源。

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While the source of the virus remains unknown, further surveillance will help in understanding its transmission, said Liang Wannian, director general of the health emergency division of China's National Health and Family Planning Commission.

WSJ: Bird Flu Found Outside China's Mainland

Diosdado Nsue-Micawg, the WHO representative in the Angolan capital of Luanda, said the health agency does not know the source of the virus, but fears that hunters and women who visit the forest might have been in contact with infected monkeys.

CNN: Ebola outbreak forces Angola to close Congo border

The two organizations have joined forces to track down the source of the Flame virus, believed by some to be the creation of a national government hostile to Iran.

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