Abstract
Adjusting for delay from confirmation to death, we estimated case and infection fatality ratios (CFR, IFR) for coronavirus disease (COVID-19) on the Diamond Princess ship as 2.6% (95% confidence interval (CI): 0.89–6.7) and 1.3% (95% CI: 0.38–3.6), respectively. Comparing deaths on board with expected deaths based on naive CFR estimates from China, we estimated CFR and IFR in China to be 1.2% (95% CI: 0.3–2.7) and 0.6% (95% CI: 0.2–1.3), respectively.
Highlights
On 1 February 2020, a patient tested positive for COVID-19 in Hong Kong; they had disembarked from the Diamond Princess cruise ship on 25 January [1,2]
After its return to Yokohama, Japan, on 3 February, the ship was held in quarantine, during which testing was performed in order to measure COVID-19 infections among the 3,711 passengers and crew members on board
We estimated that the all-age corrected IFR (cIFR) on the Diamond Princess was 1.3% (95% confidence interval (CI): 0.38–3.6) and the cCFR was 2.6% (Table 1)
Summary
On 1 February 2020, a patient tested positive for COVID-19 in Hong Kong; they had disembarked from the Diamond Princess cruise ship on 25 January [1,2]. We can estimate the true denominator for the CFR (i.e. the number of cases with known outcomes) by accounting for Figure The time-to-death distributions and case and death data used to calculate the corrected case fatality estimates, Diamond Princess cruise ship, February 2020 (n = 3,711). We assumed that the delay from confirmation to death followed the same distribution as the estimated time from hospitalisation to death, based on data from the COVID-19 outbreak in Wuhan, China, between 17 December 2019 and 22 January 2020, accounting for underestimation in the data as a result of as-yet-unknown disease outcomes (Figure, panels A and B) [7]. We considered raw ‘non-truncated’ distributions, which do not account for censoring (i.e. because of the continued growth of the outbreak, cases with shorter incubation periods are more likely to be included in the data set); the raw and truncated distributions (Supplementary Figure S1) had a mean of 8.6 days and 13 days, respectively (Supplementary Tables S1 and S2)
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