Severe underestimation of COVID-19 case numbers: effect of epidemic growth rate and test restrictions

Abstract

To understand the scope and development of the COVID-19 pandemic, knowledge of the number of infected persons is essential. Often, the number of "confirmed cases", which is based on positive RT-PCR test results, is regarded as a reasonable indicator. However, limited COVID-19 test capacities in many countries are restricting the amount of testing that can be done. This can lead to the implementation of testing policies that restrict access to COVID-19 tests, and to testing backlogs and delays. As a result, confirmed case numbers can be significantly lower than the actual number of infections, especially during rapid growth phases of the epidemic.This study examines the quantitative relation between infections and reported confirmed case numbers for two different testing strategies, "limited" and "inclusive" testing, in relation to the growth rate of the epidemic. The results indicate that confirmed case numbers understate the actual number of infections substantially; during rapid growth phases where the daily growth rate can reach or exceed 30%, as has been seen in many countries, the confirmed case numbers under-report actual infections by up to 50 to 100-fold.

Prevalence of SARS-CoV-2 among high-risk populations in Lomé (Togo) in 2020

“…Numerous assumptions have been made about the true magnitude and evolution of the epidemic around the world. It has been commonly assumed that officially reported data are underestimated [4,5], especially in Africa. The insufficient diagnostic capacity of countries and the high proportion of asymptomatic cases may explain such an underestimation [6].…”

Fear, Loss, Social Isolation, and Incomplete Grief Due to COVID-19: A Recipe for a Psychiatric Pandemic

“…In the absence of a radical comprehensive mental health response, we may observe a new epidemic of mental health problems and death of despair, defined as preventable death due to high-risk behaviors, like suicide and drug use. may have been systemically underestimated (Richterich, 2020). This number can reflect the minimum number of families who have lost a loved one due to COVID-19 by April 2020 ("COVID-19 CORONAVIRUS PANDEM-IC", 2020).…”

“…By the end of April 2020, more than 200,000 deaths caused by this disease were reported worldwide. The real number may be even higher as deaths may have been systemically underestimated ( Richterich, 2020 ). This number can reflect the minimum number of families who have lost a loved one due to COVID-19 by April 2020 ( “COVID-19 CORONAVIRUS PANDEMIC”, 2020 ).…”

A mechanistic and data-driven reconstruction of the time-varying reproduction number: Application to the COVID-19 epidemic

“…These biases are mainly due to the uncertainty in incidence data that can arise due to both the transmission characteristics of this virus (asymptomatic and pre-symptomatic transmission) and the quality and preparedness of the public health system. For COVID-19, it has been shown that the number of observed confirmed cases significantly underestimates the actual number of infections [10][11]. For instance, during the initial rapid growth phase of the COVID-19 epidemic, the number of confirmed case underestimated the actual number of infections by 50 to 100 times [10].…”

“…For COVID-19, it has been shown that the number of observed confirmed cases significantly underestimates the actual number of infections [10][11]. For instance, during the initial rapid growth phase of the COVID-19 epidemic, the number of confirmed case underestimated the actual number of infections by 50 to 100 times [10]. In France, it has been estimated that the detection rate increased from 7% in mid-May to 40% by the end of June, compared to well below 5% at the beginning of the epidemic [12].…”