Complex sentence: During a health inspection by the local port health officials up to 150 passengers were discovered to have been infected with what was presumed to be norovirus; the number of infected passengers and crew subsequently rose to 400.
Split into simpler sentences: During a health inspection by the local port health officials up to 150 passengers were discovered to have been infected with what was presumed to be norovirus. The number of infected passengers and crew subsequently rose to 400.