This disease is surprisingly difficult to catch, as most people have a natural resistance to it.

这种病令人惊讶的难以患上，因为大多数人对它有一种先天的免疫力。

《柯林斯英汉双解大词典》

They tried to catch her out with a difficult question.

他们试图用一道难题难倒她。

《牛津词典》

Zhu says that shanzhai generally is a "good thing" for consumers, though he concedes some extreme imitations cross the line to being "absolutely illegal" and their purveyors are difficult to catch.

朱先生表示山寨一般来说对于消费者而言可能是“好事”，但一旦模仿过了头就完全是违法的了，而且这些人很难被绳之于法。

youdao

While some of their clients are middle class professionals from the community at large, many brothels will only accept a narrow clientele to make it difficult for law enforcement to catch them.

VOA: standard.2010.05.24

Allocating catch shares is a difficult and often fraught process.

ECONOMIST: Fishing and conservation

"In such a short leg it was always going to be difficult to catch anyone that got away, " said skipper Smith.

BBC: Leg Seven: Dutch courage prevails