Since the beginning of the pandemic, three main transmission routes for HIV have been identified.

从HIV开始流行之初至今，人们已确认了HIV的三种主要传播途径。

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The decline could still be a temporary consequence of warm weather or half-term: pupils have been one of the main transmission routes.

这种下降可能还会是天气温暖和学生期中假的暂时结果——学生是主要的传染途径之一。

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