A third outbreak of gastrointestinal illness in less than two months has struck the National Geographic Sea Bird, sickening passengers and crew members on its July 10 voyage.
The first two outbreaks on the cruise ship have been confirmed to be caused by Norovirus, a highly contagious virus that causes inflammation of the stomach and intestines.
The cause of the most recent outbreak remains under investigation.
The CDC has recorded eight gastrointestinal illness outbreaks on cruise ships that met its public reporting threshold this year. Norovirus was identified as the cause in five cases, while two were linked to E. coli.
“Norovirus is often a cause of gastrointestinal illness outbreaks on cruise ships, but we don't always know the cause of the outbreak when we begin an investigation,” the CDC said in a statement.
Norovirus often causes acute gastroenteritis, also known as the stomach flu. The virus spreads through close contact with infected people, contaminated food or water, contaminated surfaces, and exposure to vomit or feces.
The CDC noted that finding the agent that caused an outbreak takes time. When an outbreak occurs, passengers and crew members whose symptoms meet the case definition are asked to provide stool or vomit samples, which are tested to determine the causative agent.
According to the agency, such outbreaks commonly happen in places where people are in close quarters, such as cruise ships, schools, nursing homes, hospitals, and restaurants.
The Sea Bird’s crew has since stepped up cleaning and disinfection, isolated sick passengers and crew, collected stool samples for testing, and consulted with the CDC on sanitation measures. The CDC said it is continuing to monitor the outbreak remotely.
NTD reached out to National Geographic Expeditions seeking comment but did not receive a response by publication.
The CDC notifies the public of such outbreaks when the ship is under the jurisdiction of its Vessel Sanitation Program (VSP) and the voyage has three percent or more of passengers or crew reporting symptoms of GI illness to the ship's medical staff.