They have learned that the disease is not well known or easily recognized.

他们已经知道这种病并不广为人知，或并不容易被识别。

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If only I'd had this last year I'd have known exactly how to get rid of Lavender and I would've known how to get going with . . . Well, Fred and George gave me a copy, and I've learned a lot.

如果我去年有了这本书，就会知道怎么甩掉拉文德，也会知道怎么接近……咳，弗雷德和乔治给了我一本，我弄懂了许多东西。

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