In a letter given to passengers when they boarded the P&O cruise liner Oriana ten days ago, the medical team admits that some passengers on a previous sailing had suffered from norovirus symptoms.
The company arranged for the liner to undergo an "extensive disinfection" while she was in Southampton. Some 300 passengers contracted norovirus during their trip.
As cases of the norovirus soar across the UK, fresh guidance is issued by clinicians on how to treat the symptoms.
The number of confirmed cases of the winter vomiting bug, norovirus, is 72% higher than at this time last year, health experts have said.