Epidemiology of Coronavirus Disease Outbreak among Crewmembers on Cruise Ship, Nagasaki City, Japan, April 2020

Maeda, Haruka; Sando, Eiichiro; Toizumi, Michiko; Arima, Yuzo; Shimada, Tomoe; Tanaka, Takeshi; Tashiro, Masato; Fujita, Ayumi; Yanagihara, Katsunori; Takayama, Hayato; Yasuda, Ikkoh; Kawachi, Nobuyuki; Kohayagawa, Yoshitaka; Hasegawa, Maiko; Motomura, Katsuaki; Fujita, Rie; Nakata, Katsumi; Yasuda, Jiro; Morita, Koichi; Kohno, Shigeru; Izumikawa, Koichi; Suzuki, Motoi; Morimoto, Konosuke

In April 2020, a coronavirus disease (COVID-19) outbreak occurred on the cruise ship Costa Atlantica in Nagasaki, Japan. Our outbreak investigation included 623 multinational crewmembers onboard on April 20. Median age was 31 years; 84% were men. Each crewmember was isolated or quarantined in a single room inside the ship, and monitoring of health status was supported by a remote health monitoring system. Crewmembers with more severe illness were hospitalized. The investigation found that the outbreak started in late March and peaked in late April, resulting in 149 laboratory-confirmed and 107 probable cases of infection with severe acute respiratory syndrome coronavirus 2. Six case-patients were hospitalized for COVID-19 pneumonia, including 1 in severe condition and 2 who required oxygen administration, but no deaths occurred. Although the virus can spread rapidly on a cruise ship, we describe how prompt isolation and quarantine combined with a sensitive syndromic surveillance system can control a COVID-19 outbreak.