He found a bug in his bed.
Maybe you're thinking that he's a loving man who talks only about bugs and insects, but it's not true. (Preliminary English Test; B1; Italian)
I had a stomach bug last week.
There's a bug going around.
A bug had caused the company's computer system to crash.
For instance, the millennium bug [might] make all computers confuse[d], and banks will lose money. (First Certificate in English; B2; Chinese)