SARS-CoV-2 Screening Test for Japanese Returnees From Wuhan, China, January 2020

Abstract

Background Severe acute respiratory syndrome-related coronavirus 2 (SARS-CoV-2) was found to be the causative microorganism of coronavirus disease 2019 (COVID-19), which started to spread in Wuhan, China. This study was to evaluate the effectiveness of questionnaire, symptoms-based screening, and PCR screening of returnees from COVID-19 endemic areas on a chartered flight, to examine the proportion of infected persons and the proportion of asymptomatic persons among infected persons who returned from Wuhan. Methods A retrospective cohort study was done in seven tertiary medical institutions in Japan. A total of 566 Japanese who returned from Wuhan participated in the study. Results Overall, 11 of the 566 passengers had a positive SARS-CoV-2 PCR result for pharyngeal swabs and six were asymptomatic. Only fever differed between SARS-CoV-2-positive and -negative individuals (p < 0.043). Six of the eleven PCR-positive individuals were asymptomatic and four remained positive on day 10 and One asymptomatic person tested positive up to day 27. Two of the eleven were negative on the first PCR test and positive on the second. Conclusions Our results will be important insights on screening returnees from locked down cities, as well as important data on the proportion of asymptomatic individuals infected with SARS-CoV-2. A 13-day observation period and a second round of PCR may be effective to screen patients, including asymptomatic infections.

The Proportion of SARS-CoV-2 Infections That Are Asymptomatic

“…Nineteen of the PCR-based studies collected data on symptoms longitudinally after testing, making it possible to distinguish between presymptomatic and asymptomatic infection ( 15 , 17 , 18 , 20 , 22 , 25 , 26 , 27 , 32 , 37–40 , 45 , 47 , 48 , 51 , 53 , 54 ). The follow-up period in these studies ranged from 2 to 70 days, with a median of 14 days (IQR, 14.0 to 15.8 days).…”

“…Of the 19 longitudinal studies, 14 provided information on the evolution of symptomatic status ( Table 3 ) ( 15 , 17 , 18 , 20 , 22 , 32 , 37–40 , 47 , 51 , 53 , 54 ). Among persons who tested positive but had no symptoms at the time of testing, the proportion who remained asymptomatic during a follow-up period ranged from 11.1% to 100%, with a median of 72.3% (IQR, 56.7% to 89.7%).…”

“…In 14 longitudinal studies that reported information on the evolution of symptomatic status, a median of 72.3% of persons who tested positive but had no symptoms at the time of testing remained asymptomatic during a follow-up period ( 15 , 17 , 18 , 20 , 22 , 32 , 37–40 , 47 , 51 , 53 , 54 ). If a similar proportion remained asymptomatic in the 4 large, representative, PCR-based studies, in which the median was 45.6%, the asymptomatic fraction of SARS-CoV-2 infection would be 33.0%.…”

Lessons Learned from Japan’s Response to the First Wave of COVID-19: A Content Analysis

“…This study clarified that the importance of expanding the diagnostic capacity by using university and large private laboratories and the necessity of capturing asymptomatic infections were the main topics in the early phase of the debate [ 23 , 24 , 25 ]. This corresponded to the most important issues at that point, which regarded Japan’s testing capacity [ 19 ], the identification of asymptomatic infections [ 76 , 77 , 78 , 79 , 80 , 81 , 82 ], estimates of the magnitude of COVID-19 [ 83 , 84 ], and challenges in infection control [ 85 ].…”

“…This tactic could be defended on the basis of the previous response to the H1N1 pandemic in Kobe in 2009 [ 87 ], but it was also claimed that tailor-made approaches depending on public health resources in local areas were essential to prevent citizens from rushing to hospitals [ 88 ]. Considering Japan’s experienced of a pre-symptomatic infection during the H1N1 pandemic [ 89 ] and the accumulated epidemiological data of asymptomatic infections of COVID-19 [ 76 , 77 , 78 , 79 , 80 , 81 , 82 ], the choice of restrictive access to testing as a valid measure could be debatable. As argued in expert meetings, insufficient testing caused many nosocomial and community-acquired infections [ 34 ], and incomplete reporting as well as delays in case confirmation made it challenging to capture the magnitude of the epidemic [ 12 , 90 , 91 , 92 , 93 , 94 ].…”