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

Abstract

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.

Estimation of the percentages of undiagnosed patients of the novel coronavirus (SARS-CoV-2) infection in Hokkaido, Japan by using birth-death process with recursive full tracing

“…The estimated percentages of undiagnosed symptomatic and asymptomatic patients coincided with previous studies [ 23 , 25 ]. The estimated lower bound of the total number of patients that recovered before the declaration of a state of emergency was also consistent with a previous study, which estimated that the cumulative incidence in Hokkaido was 2297 cases on February 27th [ 26 ]. One of the previous studies approximated the time evolution of the number of infected individuals with differential equations [ 23 ], while another estimated the number of asymptomatic patients by using RT-PCR (reverse transcription polymerase chain reaction) test results of evacuees from Wuhan, China on chartered flights [ 25 ].…”

The Persuasive Effect of Fox News: Non-Compliance with Social Distancing During the Covid-19 Pandemic

“…First, to the best of our knowledge, COVID-19-related cases and deaths are tracked at the more aggregate county level and not at the zipcode level. Second, at the time of writing, experts still disagreed about the accuracy and reliability of current data which would limit the interpretabilty of any association we might find with our behavioral outcomes (e.g., Nishiura et al (2020) and Akhmetzhanov et al (2020)); although Hortacsu et al (2020) have developed a promising approach to infer the number of unreported infections. Multiple studies have pointed towards the importance of social distancing for containing the disease (Matrajt and Leung, 2020;Kissler et al, 2020b).…”

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