Choose one sentence that has the same meaning as the root one:
He went down with flu as soon as he recovered from a fever.
He caught flu just before he recovered from a fever.
No sooner had he recovered from a fever than he went down with flu.
He recovered from a fever soon after he went down with flu.
He caught flu and a fever at the same time.
No sooner had he recovered from a fever than he went down with flu.