Estimating the undetected infections in the Monkeypox outbreak

Abstract

While the number of detected Monkeypox infections are widely available, an understanding of the extent of undetected cases is urgently needed for an effective tackling of its spread. The aim of this study is to estimate the true number of Monkeypox (detected and undetected) infections in most affected countries. The question being asked is: How many cases have actually occurred? We propose a lower bound estimator for the true number of Monkeypox cases. The estimator is data‐driven and can be easily computed from the cumulative distributions of weekly cases. We focused on the ratio of the total estimated cases to the observed cases on July 31, 2022: The proportion of undetected cases was relevant in all countries, with countries whose estimated true number of infections could be more than three times the observed one. We provided a practical contribution to the understanding of the current Monkeypox wave and reliable estimates on how many undetected cases are going around in several countries, where the epidemic spreads differently.

Monkeypox: Early estimation of basic reproduction number R0 in Europe

“…A retrospective analysis of the clinical cases showed April 2022 as the first evidence of MPX cases, in Portugal, in the UK, 4 and Czech Republic 13 . These index cases representing the 2022 world outbreak indicate a possibility for a larger proportion of the population infected 7 . The underestimation of the epidemic, as mentioned, can be brought back to several causes working probably together.…”

“…The simultaneous emergence of Monkeypox cases in different countries supports the hypothesis of wide viral circulation and a large number of undetected cases, due prevalently to possible detection incapability of the utilized diagnostic testing and/or to underdiagnosed clinical cases or asymptomatic infection presentation. These infected undetected asymptomatic individuals were recently estimated, 7 showing a large endemicity.…”

Evaluating undercounts in epidemics: Response to Maruotti et al. (2022)

“…), but we argue that the precise numerical values are not very important. The key aspects of a simulation are the epidemic growth rate ( ), which is the primary determinant of the ascertainment ratio bounds computed according to Maruotti et al's 2 method, and the typical number of cases reported per period, which determines the effects of the bias correction terms.…”

“…Several papers 1 , 2 , 3 have promoted formulas that claim to provide bounds on the completeness of sampling of infectious disease cases, based only on case reports. We believe these approaches are fundamentally flawed, and that it is impossible to estimate undercounting from incidence data without a specialized sampling design or some kind of auxiliary information.…”

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Maruotti et al 2022 used a mark-recapture approach to estimate bounds on the true number of monkeypox infections in various countries. We show that such approaches are fundamentally flawed.

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