During a visit by the Centers for Disease Control and Prevention the Silversea ship Silver Shadow failed to reach the pass-score of 86 out of a possible 100, scoring only 84. The inspection took place in Skagway in Alaska, in June.

The full report is not yet available but the cruise line says the score is “atypical” has issued a statement saying it is “deeply disappointed” and that is has “taken immediate measures to ensure that Silver Shadow retains the highest standards in all its operations.”

On a recent inspection in April on another of its vessels, Silversea scored 100. The last inspection on board the 382-passenger Silver Shadow, in September 2012 saw a score of 95.

Cruise ships participating in the Vessel Sanitation Program are required to report the total number of gastrointestinal (GI) illness cases evaluated by on-board medical staff before the ship arrives at a US port when sailing from a foreign port. According to VSP data Silversea is notably absent from those lines reporting outbreaks in the past five years.

In 2013 luxury cruise line Crystal Cruises, along with Royal Caribbean, Celebrity Cruises, Holland America Line (Enterotoxigenic E. coli ) and Princess Cruises are among those reporting outbreaks of Norovirus.

Thirteen cruise ships have scored a perfect 100 during this year’s inspections, including Silversea’s Silver Spirit, Disney Dream, Celebrity Eclipse, Eurodam and Carnival Freedom.

A vista suite on board Silver Shadow sailing from Alaska to Canada this September costs from £2,550.