High Probability of Long Diagnostic Delay in Coronavirus Disease 2019 Cases with Unknown Transmission Route in Japan

Abstract

Long diagnostic delays (LDDs) in patients with coronavirus disease 2019 (COVID-19) might decrease the effectiveness of patient isolation in reducing subsequent transmission. We assumed that direction of government considerably increased probability of LDD among COVID-19 cases with unknown exposure in Japan. This study aimed to investigate association of route of case detection and proportion of LDD of COVID-19 in Japan. We included confirmed COVID-19 patients with symptom onset between the ninth and eleventh week in 2020, in 6 prefectures of Japan. LDD was defined as the duration between COVID-19 symptom onset and confirmation ≥6 days. We used multivariable logistic regression analyses to elucidate factors associated with LDD. The mean diagnostic delay for 364 cases was 6.3 days. Proportion of LDD was 38% for cases with known exposure, and 65% for cases with unknown exposure. The probability of LDD in cases with unknown exposure was significantly higher than that for known exposure cases (adjusted odds ratio: 2.38, 95% confidence interval: 1.354–4.21). Early PCR test after symptom onset, strengthening of PCR test capacity, and investigations to study impact of high proportion of LDD in cases without known exposure might be necessary.

Role of stay-at-home requests and travel restrictions in preventing the spread of COVID-19 in Japan

“…The government had expanded the testing capacity since May, so the reported rates were higher in the latter three periods than before. However, given the asymptomatic nature of many infected individuals and the recommendation for consultation and medical care after the onset of symptoms for more than 4 days in Japan ( Ogata and Tanaka, 2020 , Shimizu and Negita, 2020 ), a great number of infections were not confirmed and reported. Substantial undocumented infections facilitated the spread of COVID-19, in line with previous studies ( Hao et al, 2020 , Li et al, 2020 ).…”

“…Here represents the expected number of new documented cases on day , and is the reporting delay between symptom onset date and confirmation date ( Pan et al, 2020 , Li et al, 2020 ). We set d to 4 days, because according to the guidelines for consultation and medical care regarding new coronavirus infections in Japan, people with symptoms of a cold or a fever of 37.5°C or higher for more than 4 days need to consult a public health center ( Ogata and Tanaka, 2020 , Shimizu and Negita, 2020 ). Then, the likelihood function is …”

Long Diagnostic Delay with Unknown Transmission Route Inversely Correlates with the Subsequent Doubling Time of Coronavirus Disease 2019 in Japan, February–March 2020

“…The routes of exposure were classified according to the information disclosed at the time of diagnosis as “known” (having had contact with an infected patient or visited a place of an outbreak), “imported” (from foreign countries during the incubation period), or “unknown.” We censored the data after 5 April, 2020 (the end of the 14th week) because data in two prefectures could not be retrieved in the 15th week. The number of patients with known exposures, unknown exposure, and those who were imported, were 207, 124, and 38, respectively [ 7 ].…”

“…We censored the data after 5 April, 2020 (the end of the 14th week) because data in two prefectures could not be retrieved in the 15th week. The number of patients with known exposures, unknown exposure, and those who were imported, were 207, 124, and 38, respectively [7].…”

“…The “criterion of waiting for four days” could increase the proportion of long diagnostic delay (LDD), and subsequently, the number of local patients. We reported in a previous study that the LDD for patients with unknown exposure was 65%, significantly higher than the LDD for known exposure patients (adjusted odds ratio: 2.38, 95% confidence interval [CI]: 1.354–4.21) [ 7 ].…”