Estimating the asymptomatic proportion of coronavirus disease 2019 (COVID-19) cases on board the Diamond Princess cruise ship, Yokohama, Japan, 2020

Abstract

On 5 February 2020, in Yokohama, Japan, a cruise ship hosting 3,711 people underwent a 2-week quarantine after a former passenger was found with COVID-19 post-disembarking. As at 20 February, 634 persons on board tested positive for the causative virus. We conducted statistical modelling to derive the delay-adjusted asymptomatic proportion of infections, along with the infections’ timeline. The estimated asymptomatic proportion was 17.9% (95% credible interval (CrI): 15.5–20.2%). Most infections occurred before the quarantine start.

Estimation of SARS-CoV-2 mortality during the early stages of an epidemic: a modeling study in Hubei, China, and six regions in Europe

“…Under 20 years of age, mortality among symptomatics is estimated below 1 in 1,000 and rises to between 3 to 8 per 1,000 symptomatic infections for individuals aged 20 to 49 years. Mortality among symptomatics is estimated to 2.5% (95%CrI: 1.9-3.1) among individuals aged 50-59, 8.0% (95%CrI: 6.6-9.5) among individuals aged 60-69, 19.2% (95%CrI: 15.8-22.9) among individuals aged 70-79 and reaches 39.0% (95%CrI: 31.1-48.9) among individuals aged 80 and more. The estimated prevalence of the four comorbidities is shown in Figure 3C.…”

“…First, we implemented age-specific risks of transmission through a contact matrix, which partially explains the age patterns in reported Covid-19 cases and leads to lower estimates of the total number of infections, thus increasing mortality. Second, a higher estimated proportion of symptomatic people, based on new studies [19,18], also led to higher estimates of mortality among all infected.…”

Modelling the Potential Health Impact of the COVID-19 Pandemic on a Hypothetical European Country

“…would be more likely to transmit infection. Of note is an estimate from the Diamond Princess cruise ship outbreak, that 17.9% of COVID-19 infections were from asymptomatic individuals (95% credible interval 15.5-20.2%) [27]. But it is unclear how generalisable this finding is given the crowded cruise ship conditions and the typically elderly nature of the passengers.…”

Diagnosing COVID-19: The Disease and Tools for Detection

“…Asymptomatic individuals are as infectious as symptomatic individuals and are therefore capable of further spreading the disease. 6 SARS-CoV-2 can be transmitted from human to human. The current hypothesis is that the first transmission occurred between bats and a yet-to-be-determined intermediate host animal.…”