'bad flu' is correct and usable in written English.
For example, you could use it in the sentence "He had a bad flu that kept him home from school for a week."
Most of their stories probably translate to any western nation – a car accident, a bad flu, a sick child.
There are more than 100 viruses that can cause "colds and flu" symptoms — though a bad flu is worse than most of them.
Not that I was all that bothered about it, but Nadezda got bad flu, and when I visited her at her grandmother's we would watch the games.
Leyla has little doubt that the origins of her condition were physical - a bad flu, leading, perhaps, to an inner ear problem with odd neurological effects.
And I think having the government shut down — particularly during a bad flu season, in a setting of outbreaks — could very well cost American lives.
"I felt that she gave a tentative performance," Mr. Weissler said, "but obviously that's what happens when you're out for a week with a bad flu".
Officially the Palestinians have said only that Mr. Arafat is suffering from a bad stomach flu.
And it made my friend very sick, very quickly, with what looked like a bad stomach flu, but included blood and heart complications.
Officially, the Palestinians have said only that Mr. Arafat is suffering from a bad stomach flu despite the body of evidence that he is afflicted with something more serious.
Doctors will be closely watching the figures as children return to school for an indication of how bad the flu season will be.
The news is bad for flu vaccinations and it's even worse for others.
