If you do have it, the disease will always have onset by age 40, 50 or what have you.

如果你有的话，这个病就会从40岁，50岁之类的年纪0,开始发作。

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But it could also be that it wasn't as easily diagnosed then.

这也同样有可能因为,在那个年代这种病不容易诊断出来

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There weren't people that got infected, like you can get infected with hepatitis B or tuberculosis, and not even know you're infected.

这不像人们感染了,像B型肝炎或者肺结核这类病时,都有可能不知道自己被感染了

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