TB is a serious illness, but it can be cured.

肺结核虽然是一种严重的疾病，但可治愈。

《牛津词典》

A very high temperature often denotes a serious illness.

高烧常常说明病得很重。

《牛津词典》

The little girl got a serious illness.

这个小女孩得了重病。

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CDC spokesman Christopher Cox says though the idea is well-intentioned, it is not a good way to protect against serious illness.

VOA: standard.2009.12.18

I had just gotten over a serious illness that I won't bother to talk about except that it had something to do with the miserably weary splitting up and my feeling that everything was dead.

我刚熬过一场重大疾病，具体就不说了,只是这与我和妻子不幸的分离有些关系,我感觉万物都没有了生机。

耶鲁公开课 - 1945年后的美国小说课程节选

She lived in New York for a short time, but she was afflicted with lupus, a very serious illness, and she died at the age of 39 in 1964.

她在纽约度过一段短暂的时光，但她饱受狼疮，一种严重疾病的折磨，最终逝世于1964年。

耶鲁公开课 - 1945年后的美国小说课程节选

Whooping cough, also known as pertussis, can be a serious illness, especially in the very young.

BBC: Whooping cough cases increase in England and Wales

The Dutch goalkeeper recently returned to action following a serious illness suffered by his wife Annemarie.

BBC: Sunday's gossip column - transfers and rumours

Now, of course, the caution to all of this is that depression is a serious illness.

NPR: Can Botox Treat Depression Along with Wrinkles?