You catch a cold when a virus infects your upper respiratory system.

当上呼吸系统感染了病毒，人就会得感冒。

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When a virus attacks your body, your body works hard to get rid of it.

当病毒攻击你的身体时，你的身体会努力摆脱它。

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When a virus attacks your body, your body works hard to get rid of it.

当病毒攻击你的身体时，你的身体会努力摆脱它。

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