At least 89 passengers on board Saga’s Spirit of Discovery have been struck down with suspected norovirus.
The passengers are reported to be suffering from vomiting, diarrhoea and fever.
The ship, which launched last year, is due back in Southampton on Wednesday.
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The ship has been cruising around Italy and Spain and was refused entry to Gibraltar on Saturday.
The ship has 868 passengers and 513 crew on board.
A spokeswoman from Saga said: “We have a number of individuals suffering from a gastrointestinal illness on board Spirit of Discovery, following her recent cruise to Italy.
“Due to the possibility that this could be caused by the Winter Vomiting Bug, the second most frequently reported illness after the common cold, the Port of Gibraltar took the decision not to allow passengers to leave the ship.
“As a result she continued with her journey towards Southampton which was our next port of call concluding this cruise.
“Our high hygiene standards and well-practised procedures mean that the illness has remained contained. The health of our customers is of paramount importance to us and we shall continue to take all appropriate steps to ensure their well-being.”
A Gibraltar government spokesperson told the Mail: “As it neared Gibraltar, the cruise ship, Spirit of Discovery, reported that, on board, it had 89 cases of suspected norovirus (diarrhoea, vomiting and fever).
“However, given the current situation, the vessel has been asked to continue to its next port of call, Southampton, without berthing at Gibraltar.”
The spokesperson stressed that the symptoms are not those of coronavirus.
Norovirus, also known as the winter vomiting bug, is one of the most common stomach infections in the UK.
It spreads from person to person by through close contact, coughing and sneezing and touching the same surfaces or food as someone who has the illness.