Closed environments facilitate secondary transmission of coronavirus disease 2019 (COVID-19)

Nishiura, Hiroshi; Oshitani, Hitoshi; Kobayashi, Tetsuro; Saito, Tomoya; Sunagawa, Tomimasa; Matsui, Takeshi; Wakita, Takaji; Team, Mhlw Covid Response; Suzuki, Motoi

doi:10.1101/2020.02.28.20029272

Cited by 320 publications

(311 citation statements)

References 2 publications

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“…It was considered that identifying clusters occurring in Japan with monitoring and isolating close contacts with the identified patients were prudent strategy and it would be able to comprehend the trend of COVID-19 infections in Japan. 4 However, since difference between those who were identified and those who actually had infections was so huge according to our findings, Japan might not have comprehended the epidemic dynamics occurring in the nation.…”

Section: Discussionmentioning

confidence: 63%

Seroprevalence of novel coronavirus disease (COVID-19) in Kobe, Japan

Doi

Iwata

Kuroda

et al. 2020

Preprint

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Background: Coronavirus disease 2019 pandemic caused by SARS-CoV-2 has been affecting many people on earth and our society. Japan is known to have relatively less number of infections as well as deaths among developed nations. However, accurate prevalence of in Japan remains unknown. Therefore, we conducted a cross-sectional study to estimate seroprevalence of SARS-CoV-2 infection. Methods:We conducted a cross-sectional serologic testing for SARS-CoV-2 antibody using 1,000 samples from patients at outpatient settings who visited the clinic from March 31 to April 7, 2020, stratified by the decade of age and sex.Results: There were 33 positive IgG among 1,000 serum samples (3.3%, 95%CI: 2.3-4.6%). By applying this figure to the census of Kobe City (population: 1,518,870), it is estimated that the number of people with positive IgG be 50,123 (95%CI: 34,934-69,868). Age and sex adjusted prevalence of positivity was calculated 2.7% (95%CI: 1.8-3.9%), and the estimated number of people with positive IgG was 40,999 (95%CI: 27,221). These numbers were 396 to 858 fold more than confirmed cases with PCR testing in Kobe City. Conclusions:Our cross-sectional serological study suggests that the number of people with seropositive for SARS-CoV-2 infection in Kobe, Japan is far more than the confirmed cases by PCR testing.All rights reserved. No reuse allowed without permission.was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity.

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Section: Discussionmentioning

confidence: 63%

Seroprevalence of novel coronavirus disease (COVID-19) in Kobe, Japan

Doi

Iwata

Kuroda

et al. 2020

Preprint

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“…Assuming our estimates are correct, a substantial proportion of these infected persons likely had only a mild or asymptomatic course of disease [9,17] and therefore did not seek medical care and were not detected by the surveillance system. Preliminary analysis of the offspring distribution among infected individuals in the detected clusters around Japan has shown that approximately 80% of cases do not produce secondary infections (i.e., their reproduction number is equal to zero) [50]. Because most of the clusters have been linked to the known cases and could be traced back in time, we argue that there is still a window of opportunity for containment of the disease and only some small fraction of the infections may drive the epidemic [14].…”

Section: Discussionmentioning

confidence: 99%

Estimation of the actual incidence of coronavirus disease (COVID-19) in emergent hotspots: The example of Hokkaido, Japan during February–March 2020

Akhmetzhanov

Mizumoto

Jung

et al. 2020

Preprint

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Following the first report of coronavirus disease 2019 in Sapporo City, Hokkaido Prefecture, Japan on 14 February 2020, a surge of cases was observed in Hokkaido during February and March. As of 6 March, 90 cases were diagnosed in Hokkaido. Unfortunately, many infected persons may not have been recognized as cases due to having mild or no symptoms. We therefore estimated the actual number of COVID-19 cases in (i) Hokkaido Prefecture and (ii) Sapporo City using data on cases diagnosed outside these areas. The estimated cumulative incidence in Hokkaido as of 27 February was 2297 cases (95% confidence interval [CI]: 382, 7091) based on data on travelers outbound from Hokkaido. The cumulative incidence in Sapporo City as of 28 February was estimated at 2233 cases (95% CI: 0, 4893) based on the count of confirmed cases within Hokkaido. Both approaches resulted in similar estimates, indicating higher incidence of infections in Hokkaido than were detected by the surveillance system. This quantification of the gap between detected and estimated cases can help inform public health response as it provides insight into the possible scope of undetected transmission.

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“…Our R 0 obtained before VECSC was smaller than the previous studies , however, reproduction numbers in VECSC period and after VECSC were almost comparable. However, an earlier study [11] estimated R 0 in Japan All rights reserved. No reuse allowed without permission.…”

Section: Discussionmentioning

confidence: 96%

Effect of emergency declaration for the COVID-19 outbreak in Tokyo, Japan in the first two weeks

Kurita

Sugawara

Ohkusa

2020

Preprint

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Background: Japan's Prime Minister Abe declared an emergency to control the COVID-19 outbreak on April 7, 2020. He asked almost half of the population of Japan to reduce their personal contacts by 70-80%.Object: This study estimates the effectiveness of that emergency declaration.Method: We applied a simple susceptible-infected-recovery model to data of patients with symptoms in Tokyo, Japan for January 14 -April 21 as of April 22. We estimate the reproduction number in four periods: R 0 before voluntary event cancellation and school closure (VECSC) which was introduced since February 27 to March 19, R v during the VECSC, R a after VECSC, and R e after the emergency declaration.Results: Results suggest that the value of R 0 was estimated as 1.267; its range was [1.214, 1.341]. However, R v was estimated as 2.360 [1.844, 2.623]. R a was estimated as 2.307 [2.035, 2.794] and R e was 0.462 [0.347, 0.514].Discussion and Concussion: One must be reminded that these results reflect only those at two weeks after the emergency declaration. The reproduction number probably changed thereafter continuously.

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Closed environments facilitate secondary transmission of coronavirus disease 2019 (COVID-19)

Cited by 320 publications

References 2 publications

Seroprevalence of novel coronavirus disease (COVID-19) in Kobe, Japan

Seroprevalence of novel coronavirus disease (COVID-19) in Kobe, Japan

Estimation of the actual incidence of coronavirus disease (COVID-19) in emergent hotspots: The example of Hokkaido, Japan during February–March 2020

Effect of emergency declaration for the COVID-19 outbreak in Tokyo, Japan in the first two weeks

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