flu不能这样用,“得了重流感”可用a bad bout/dose/case of (the) flu。例如:
I had a bad case of the flu. 我得了重流感。《新牛津美语大词典》
She's had a nasty dose of flu.(BrE)他得了重流感。《牛津英语搭配词典》
She's had a nasty dose of the flu.(AmE)他得了重流感。《牛津英语搭配词典》
He came down with a bad bout/attack/case of the flu. 他患重度的流行性感冒。《韦氏高阶英汉双解词典》