Investigation of the use of PCR testing prior to ship boarding to prevent the spread of SARS-CoV-2 from urban areas to less-populated remote islands.

Preventing coronavirus disease (COVID-19) outbreaks and the spread of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) from urban areas to less-populated remote islands, many of which may have weak medical systems, is an important issue. Here, we evaluated the usefulness of pre-boarding, saliva-based polymerase chain reaction (PCR) screening tests to prevent the spread of SARS-CoV-2 from Tokyo to the remote island of Chichijima. The infection rate on the island during the study period from September 1, 2020 to March 21, 2021 was 0.015% (2/13,446). Of the 8,910 individuals tested before ship boarding, seven tested positive for COVID-19 (PCR tests of saliva samples). One was confirmed positive by subsequent confirmatory nasopharyngeal swab testing. Based on the testing results, positive cases were denied entry onto the ship to prevent the spread of COVID-19 from Tokyo to Chichijima. This study demonstrated that implementing pre-boarding PCR screening tests is a useful strategy that can be applied to other remote islands with vulnerable medical systems.