Objectives: Cruise ship settings can facilitate transmission of respiratory infections. In March 2020, a COVID-19 outbreak occurred on the Grand Princess cruise ship. We describe the public health response, including a large-scale US federal quarantine intended to limit spread to communities not yet affected by COVID-19.
Methods: All US residents and symptomatic people requiring hospitalization disembarked beginning on March 9 and were transported to designated US military bases for federal quarantine or to hospitals or alternate care sites for medical care. Foreign nationals remained on board (crew) or were repatriated (passengers). People under federal quarantine were monitored daily for symptoms and tested voluntarily for SARS-CoV-2 upon arrival, as tests became available, and if symptoms developed.
Results: Of 3582 travelers (passengers and crew) on board, 2013 (56%) went to military bases, 59 (2%) went to hospitals or alternate care sites, 419 (12%) were repatriated, and the remainder (crew) quarantined on board. Overall, 1144 travelers (32%) were tested for SARS-CoV-2; of those, 155 (14%) had a positive test result. Among 2013 US residents quarantined, 1054 (52%) were tested. Of those, 115 (11%) had a positive test result, 37 (32%) of whom were symptomatic at testing. Proportions tested across bases ranged from 28% to 89%; test positivity ranged from 10% to 16%. Of 31 travelers hospitalized, the median (IQR) stay was 4 (4-9) nights, and 9 (29%) travelers died of SARS-CoV-2 complications.
Conclusions: The Grand Princess outbreak was the first confirmed COVID-19 outbreak on a cruise ship in US waters. Multiagency public health responses allowed for isolation and quarantine, potentially helping to slow transmission into US communities. Ensuring that cruise ships have plans for communicable disease control and mitigation helps protect passenger and crew well-being.
Keywords: COVID-19; SARS-CoV-2; cruise ship; outbreak; quarantine.