Complex sentence: They both had flu-symptoms, and when the living man from Pandrup arrived at Aalborg Sygehus, he tested positive on H1N1, although it is still not known if the passenger who died caused the flu.
Split into simpler sentences: They both had flu-symptoms, and when the living man from Pandrup arrived at Aalborg Sygehus, he was tested positive on H1N1. Although, it is still not known, if the passenger died caused the flu.