Potential transmission of SARS-CoV-2 on a flight from Singapore to Hangzhou, China: An epidemiological investigation

Abstract

Background: Between January 24, 2020 and February 15, 2020, an outbreak of COVID-19 occurred among 335 passengers on a flight from Singapore to Hangzhou in China. This study aimed to investigate the source of the outbreak and assess the risk of transmission of COVID-19 during the flight.

Method: Using a standardized questionnaire, we collected information on the travelers' demographic characteristics and illness before, during, and after the flight. We also collected data on factors potentially associated with COVID-19 transmission during the flight.

Results: A total of 16 COVID-19 patients were diagnosed among all passengers; the overall attack rate was 4.8%. The attack rate among passengers who had departed from Wuhan was significantly higher than that among those who had departed from other places. One passenger without an epidemiological history of exposure before boarding developed COVID-19. During the flight, he was seated near four infected passengers from Wuhan for approximately an hour and did not wear his facemask correctly during the flight.

Conclusions: COVID-19 transmission may have occurred during the flight. However, the majority of the cases in the flight-associated outbreak could not be attributed to transmission on the flight but were associated with exposure to the virus in Wuhan or to infected members in a single tour group.

Keywords: Air travel; COVID-19; Outbreak investigation; Travel-associated infections.

Fig. 1

Epidemic curve indicating the date of onset of COVID-19 cases among passengers on the flight, January to February 2020. (A): The case passengers flew from China to Singapore on 19 January (One passenger departed from Hangzhou; and the remaining 15 case passengers departed from Wuhan.). (B): The flight departed from Singapore to Hangzhou on 24 January and the passengers were placed in medical isolation and under observation on arrival in Hangzhou. (C): All passengers had samples collected for testing on 26 January. (D): All passengers had a second set of samples collected on 6 February. (E): The passengers from places other than Wuhan ended their medical isolation on 8 February. (F): Those who departed from Wuhan ended their medical isolation one week later on 15 February.

Fig. 2

Aircraft configuration and the location of the seats where the 16 case passengers sat during the flight. The numbers in the red background correspond to the Case number shown in Table 1. (For interpretation of the references to colour in this figure legend, the reader is referred to the Web version of this article.)