Gastro outbreak hits guests on cruise ship

A 12-day round trip from Brisbane to Papua New Guinea has finished on a sour note for some cruise passengers following a gastro outbreak.

Almost 100 Australian passengers on a cruise ship have been struck down by a gastro virus. (AAP)

Almost 100 Australian passengers on a cruise ship have been struck down by a gastro virus that plagued the end of a 12-day voyage to Papua New Guinea.

The Sun Princess docked in Brisbane on Thursday and was given a thorough clean after all 2000 guests disembarked.

Carnival Australia admitted a relatively "small number" of guests and some staff were affected by norovirus in the closing days of the round trip, and the ship was given a deep cleanse during its turnaround before a 14-day cruise to New Zealand.