Estimation of the asymptomatic ratio of novel coronavirus infections (COVID-19)

Nishiura, Hiroshi; Kobayashi, Tetsuro; Miyama, Takeshi; Suzuki, Ayako; Jung, Sung-mok; Hayashi, Katsuma; Kinoshita, Ryô; Yang, Yichi; Yuan, Baoyin; Akhmetzhanov, Andrei R.; Linton, Natalie M.

doi:10.1101/2020.02.03.20020248

Cited by 647 publications

(784 citation statements)

References 7 publications

(7 reference statements)

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“…Our estimated asymptomatic proportion is at 17.9% (95% CrI: 15.5%-20.2%), which overlaps with a recently derived estimate of 33.3% (95% CI: 8.3%-58.3%) from data of Japanese citizens evacuated from Wuhan [13]. Considering the similarity in viral loads and the high possibility of potent transmission potential, the high proportion of asymptomatic infections has significant public health implications [14].…”

Section: Discussionsupporting

confidence: 77%

Estimating the Asymptomatic Proportion of 2019 Novel Coronavirus onboard the Princess Cruises Ship, 2020

Mizumoto

Kagaya

Zarebski

et al. 2020

Preprint

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The potential infectiousness of asymptomatic COVID-19 cases together with a substantial fraction of asymptomatic infections among all infections, have been highlighted in clinical studies. We conducted statistical modeling analysis to derive the delay-adjusted asymptomatic proportion of the positive COVID-19 infections onboard the Princess Cruises ship along with the timeline of infections. We estimated the asymptomatic proportion at 17.9% (95% CrI: 15.5%-20.2%), with most of the infections occurring before the start of the 2-week quarantine. Word count: Abstract: 75Main:

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Section: Discussionsupporting

confidence: 77%

Estimating the Asymptomatic Proportion of 2019 Novel Coronavirus onboard the Princess Cruises Ship, 2020

Mizumoto

Kagaya

Zarebski

et al. 2020

Preprint

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“…Based on these results, we calibrate the proportion of asymptomatic infections for individuals 20 years and older across the range of 20% to 40%. This range is also supported byNishiura et al (2020), which found that 30.8% (95% CI: 7.7, 53.8) of infected individuals among Japanese citizens evacuated from Wuhan, China were asymptomatic.…”

supporting

confidence: 60%

Defining high-value information for COVID-19 decision-making

Salomon¹

2020

Preprint

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Initial projections from the first generation of COVID-19 models focused public attention on worst-case scenarios in the absence of decisive policy action. These underscored the imperative for strong and immediate measures to slow the spread of infection. In the coming weeks, however, as policymakers continue enlisting models to inform decisions on COVID-19, answers to the most difficult and pressing policy questions will be much more sensitive to underlying uncertainties. In this study, we demonstrate a model-based approach to assessing the potential value of reducing critical uncertainties most salient to COVID-19 decision-making and discuss priorities for acquiring new data to reduce these uncertainties. We demonstrate how information about the impact of non-pharmaceutical interventions could narrow prediction intervals around hospitalizations over the next few weeks, while information about the prevalence of undetected cases could narrow prediction intervals around the timing and height of the peak of the epidemic.

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“…20 Asymptomatic individuals were able to infect at a 50% reduced rate compared with their symptomatic counterparts based on estimates from Nishiura and colleagues. 23 We also investigated four alternate asymptomatic proportions: 22·7%, as reported by Furuya-Kanamori and colleagues 24 for influenza A H1N1 in a pooled prevalence study; and 30·0%, 40·0%, and 50·0%, as potential but theoretical proportions to investigate intervention efficacy with a high fraction of infections that are cryptic and undetectable.…”

Section: Sars-cov-2 Infection Parametersmentioning

confidence: 98%

Interventions to mitigate early spread of SARS-CoV-2 in Singapore: a modelling study

Koo

Cook

Park

et al. 2020

The Lancet Infectious Diseases

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688

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Background Since the coronavirus disease 2019 outbreak began in the Chinese city of Wuhan on Dec 31, 2019, 68 imported cases and 175 locally acquired infections have been reported in Singapore. We aimed to investigate options for early intervention in Singapore should local containment (eg, preventing disease spread through contact tracing efforts) be unsuccessful. MethodsWe adapted an influenza epidemic simulation model to estimate the likelihood of human-to-human transmission of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in a simulated Singaporean population. Using this model, we estimated the cumulative number of SARS-CoV-2 infections at 80 days, after detection of 100 cases of community transmission, under three infectivity scenarios (basic reproduction number [R 0 ] of 1•5, 2•0, or 2•5) and assuming 7·5% of infections are asymptomatic. We first ran the model assuming no intervention was in place (baseline scenario), and then assessed the effect of four intervention scenarios compared with a baseline scenario on the size and progression of the outbreak for each R 0 value. These scenarios included isolation measures for infected individuals and quarantining of family members (hereafter referred to as quarantine); quarantine plus school closure; quarantine plus workplace distancing; and quarantine, school closure, and workplace distancing (hereafter referred to as the combined intervention). We also did sensitivity analyses by altering the asymptomatic fraction of infections (22·7%, 30·0%, 40·0%, and 50·0%) to compare outbreak sizes under the same control measures.Findings For the baseline scenario, when R 0 was 1·5, the median cumulative number of infections at day 80 was 279 000 (IQR 245 000-320 000), corresponding to 7•4% (IQR 6·5-8·5) of the resident population of Singapore. The median number of infections increased with higher infectivity: 727 000 cases (670 000-776 000) when R 0 was 2·0, corresponding to 19•3% (17•8-20•6) of the Singaporean population, and 1 207 000 cases (1 164 000-1 249 000) when R 0 was 2·5, corresponding to 32% (30•9-33•1) of the Singaporean population. Compared with the baseline scenario, the combined intervention was the most effective, reducing the estimated median number of infections by 99•3% (IQR 92•6-99•9) when R 0 was 1·5, by 93·0% (81•5-99•7) when R 0 was 2·0, and by 78•2% (59·0 -94•4) when R 0 was 2·5. Assuming increasing asymptomatic fractions up to 50·0%, up to 277 000 infections were estimated to occur at day 80 with the combined intervention relative to 1800 for the baseline at R 0 of 1·5.Interpretation Implementing the combined intervention of quarantining infected individuals and their family members, workplace distancing, and school closure once community transmission has been detected could substantially reduce the number of SARS-CoV-2 infections. We therefore recommend immediate deployment of this strategy if local secondary transmission is confirmed within Singapore. However, quarantine and workplace distancing should be prioritised over school cl...

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Estimation of the asymptomatic ratio of novel coronavirus infections (COVID-19)

Cited by 647 publications

References 7 publications

Estimating the Asymptomatic Proportion of 2019 Novel Coronavirus onboard the Princess Cruises Ship, 2020

Estimating the Asymptomatic Proportion of 2019 Novel Coronavirus onboard the Princess Cruises Ship, 2020

Defining high-value information for COVID-19 decision-making

Interventions to mitigate early spread of SARS-CoV-2 in Singapore: a modelling study

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