About 300 of the 1,843 travellers aboard the P&O liner Oriana on a 10-night Baltic cruise contracted the norovirus bug, a spokeswoman for P&O Cruises said, after the ship docked in Southampton.
The company said the illness had been "mild" and just five passengers still had "active symptoms" on Friday.
"There has been an incidence of a mild gastrointestinal illness among the passengers on Oriana. This illness is suspected to be Norovirus, which is highly contagious and typically transmitted from person to person.
"Norovirus is common throughout the UK, Europe and North America and has affected a number of schools, hospitals, nursing homes and children's day care centres," according to the statement.
Passenger Paul Gilman, 62, told the Daily Mail newspaper on Thursday: "It has been outrageous from start to finish. People were falling like flies, yet the crew were trying to insist everything was fine.
"Everyone is saying, 'this is a plague ship'. It's a living nightmare."
Passenger Brian Weston, 67, told the Daily Mail: "It's been a shambles from start to finish. Passengers became ill almost immediately we set sail and the outbreak swept like wildfire through the ship.
His wife, Denise, 60, said: "A viral specialist who is a passenger told us the ship should not have set sail for 48 hours and should have gone through a deep clean."
P&O insisted that measures had been taken on board to attempt to minimise transmission of the virus.
"As is currently standard procedure across our fleet, all the ship's passengers were provided with a precautionary health notice advising of widespread norovirus activity and the health measures to avoid contraction and spread, both on board and while ashore," the P&O spokeswoman said.
Oriana had left Southampton on December 4, with tickets costing up to £1,400 (1,725 euros, $2,257).
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