After being ill, the child has been all droopy and weak.
Tips
memory
蔫 (niān) is what wilted vegetables and droopy flowers do — the 艹 grass radical on top is your hint. The reduplicated 呼呼 hūhū is a stative-adjective suffix (as in 热呼呼 'piping hot,' 软呼呼 'all soft'). Put together: 'wilted-wilted' = drooping in spirit.
register
Northern colloquial. Describes a person whose energy or initiative has gone limp, not so much physical illness.
