Covid-19 was likely transmitted first from passengers to crew members and subsequently spread among food service workers on the cruiseship Diamond Princess, according to a report by the US Centers for Disease Control and Prevention (CDC).
The outbreak of the virus on the cruiseship on 3 February led to the quarantine of approximately 3,700 passengers and crew which lasted for nearly four weeks at the Port of Yokohama, Japan. By 9 February, there were 20 confirmed cases among the ship’s crew members.
By the end of quarantine, approximately 700 cases of Covid-19 had been laboratory-confirmed among passengers and crew.
‘Because the first detected cases occurred among passengers who became symptomatic on 22 and 23 January, Covid-19 was likely transmitted first from passengers to crew members and subsequently spread among the crew, especially among food service workers,’ the report found. ‘The first case detected in a crew member occurred in a food service worker who developed fever on 2 February.’
The crew dining area was identified as the primary area of congregation for the crew. Passengers did not have access to this part of the ship.
Up to 15 of the 20 confirmed cases in crew members occurred among food service workers who prepared food for other crew members and passengers. While 16 of the 20 cases occurred among persons with cabins on deck 3, the deck on which the food service workers lived.
Eight of 20 crew members with confirmed Covid-19 had cabin mates and investigators later learned that following disembarkation as of March 4 five of the eight cabin mates had also developed Covid-19.
CDC recommended that people who develop Covid-19 symptoms while on board a ship should be isolated to limit transmission to other passengers and crew.
In early March most cruise companies suspended operations in response to the pandemic.