An estimated 30 million passengers are transported on 272 cruise ships worldwide each year. Cruise ships bring diverse populations into proximity for many days, facilitating transmission of respiratory illness. SARS-CoV-2, the virus that causes coronavirus disease (COVID-19) was first identified in Wuhan, China, in December 2019 and has since spread worldwide to at least 187 countries and territories.
Widespread COVID-19 transmission on cruise ships has been reported as well. Passengers on certain cruise ship voyages might be aged ≥65 years, which places them at greater risk for severe consequences of SARS-CoV-2 infection. During February–March 2020, COVID-19 outbreaks associated with three cruise ship voyages have caused more than 800 laboratory-confirmed cases among passengers and crew, including 10 deaths.
Transmission occurred across multiple voyages of several ships. This report describes public health responses to COVID-19 outbreaks on these ships. COVID-19 on cruise ships poses a risk for rapid spread of disease, causing outbreaks in a vulnerable population, and aggressive efforts are required to contain spread. All persons should defer all cruise travel worldwide during the COVID-19 pandemic.
During February 7–23, 2020, the largest cluster of COVID-19 cases outside mainland China occurred on the Diamond Princess cruise ship, which was quarantined in the port of Yokohama, Japan, on February 3. On March 6, cases of COVID-19 were identified in persons on the Grand Princess cruise ship off the coast of California; that ship was subsequently quarantined. By March 17, confirmed cases of COVID-19 had been associated with at least 25 additional cruise ship voyages.
On February 21, CDC recommended avoiding travel on cruise ships in Southeast Asia; on March 8, this recommendation was broadened to include deferring all cruise ship travel worldwide for those with underlying health conditions and for persons aged ≥65 years. On March 13, the Cruise Lines International Association announced a 30-day voluntary suspension of cruise operations in the United States. CDC issued a level 3 travel warning on March 17, recommending that all cruise travel be deferred worldwide.
On January 20, 2020, the Diamond Princess cruise ship departed Yokohama, Japan, carrying approximately 3,700 passengers and crew (Table). On January 25, a symptomatic passenger departed the ship in Hong Kong, where he was evaluated; testing confirmed SARS-CoV-2 infection. On February 3, the ship returned to Japan, after making six stops in three countries. Japanese authorities were notified of the COVID-19 diagnosis in the passenger who disembarked in Hong Kong, and the ship was quarantined. Information about social distancing and monitoring of symptoms was communicated to passengers.
On February 5, passengers were quarantined in their cabins; crew continued to work and, therefore, could not be isolated in their cabins. Initially, travelers with fever or respiratory symptoms and their close contacts were tested for SARS-CoV-2 by reverse transcription–polymerase chain reaction (RT-PCR).
All those with positive test results were disembarked and hospitalized. Testing was later expanded to support a phased disembarkation of passengers, prioritizing testing of older persons, those with underlying medical conditions, and those in internal cabins with no access to the outdoors. During February 16–23, nearly 1,000 persons were repatriated by air to their home countries, including 329 persons who returned to the United States and entered quarantine or isolation.
The remaining passengers who had negative SARS-CoV-2 RT-PCR test results, no respiratory symptoms, and no close contact with a person with a confirmed case of COVID-19 completed a 14-day ship-based quarantine before disembarkation.
Those passengers who had close contact with a person with a confirmed case completed land-based quarantine, with duration determined by date of last contact. After disembarkation of all passengers, crew members either completed a 14-day ship-based quarantine, were repatriated to and managed in their home country, or completed a 14-day land-based quarantine in Japan.
Overall, 111 (25.9%) of 428 U.S. citizens and legal residents did not join repatriation flights either because they had been hospitalized in Japan or for other reasons. To mitigate SARS-CoV-2 importation into the United States, CDC used temporary “Do Not Board” restrictions (7) to prevent commercial airline travel to the United States,†† and the U.S. Departments of State and Homeland Security restricted travel to the United States for non-U.S. travelers.
Among 3,711 Diamond Princess passengers and crew, 712 (19.2%) had positive test results for SARS-CoV-2 (Figure 1). Of these, 331 (46.5%) were asymptomatic at the time of testing. Among 381 symptomatic patients, 37 (9.7%) required intensive care, and nine (1.3%) died (8). Infections also occurred among three Japanese responders, including one nurse, one quarantine officer, and one administrative officer (9). As of March 13, among 428 U.S. passengers and crew, 107 (25.0%) had positive test results for COVID-19; 11 U.S. passengers remain hospitalized in Japan (median age = 75 years), including seven in serious condition (median age = 76 years).
During February 11–21, 2020, the Grand Princess cruise ship sailed roundtrip from San Francisco, California, making four stops in Mexico (voyage A). Most of the 1,111 crew and 68 passengers from voyage A remained on board for a second voyage that departed San Francisco on February 21 (voyage B), with a planned return on March 7 (Table). On March 4, a clinician in California reported two patients with COVID-19 symptoms who had traveled on voyage A, one of whom had positive test results for SARS-CoV-2. CDC notified the cruise line, which began cancelling group activities on voyage B.
More than 20 additional cases of COVID-19 among persons who did not travel on voyage B have been identified from Grand Princess voyage A, the majority in California. One death has been reported. On March 5, a response team was transported by helicopter to the ship to collect specimens from 45 passengers and crew with respiratory symptoms for SARS-CoV-2 testing; 21 (46.7%), including two passengers and 19 crew, had positive test results.
Passengers and symptomatic crew members were asked to self-quarantine in their cabins, and room service replaced public dining until disembarkation. Following docking in Oakland, California, on March 8, passengers and crew were transferred to land-based sites for a 14-day quarantine period or isolation.
Persons requiring medical attention for other conditions or for symptoms consistent with COVID-19 were evaluated, tested for SARS-CoV-2 infection, and hospitalized if indicated. During land-based quarantine in the United States, all persons were offered SARS-CoV-2 testing. As of March 21, of 469 persons with available test results, 78 (16.6%) had positive test results for SARS-CoV-2.
Repatriation flights for foreign nationals were organized by several governments in coordination with U.S. federal and California state government agencies. Following disinfection of the vessel according to guidance from CDC’s Vessel Sanitation Program, remaining foreign nationals will complete quarantine on board. The quarantine will be managed by the cruise company, with technical assistance provided by public health experts.
On February 21, five crew members from voyage A transferred to three other ships with a combined 13,317 passengers on board. No-sail orders were issued by CDC for these ships until medical logs were reviewed and the crew members tested negative for SARS-CoV-2.