Objective:

To analyze the increase in sentinel cases of COVID-19 in Mexico calculated from the effective number of reproductions of the infection (Rt) and compare its evolution with that reported by Italy, Spain and the United States of America during the first twenty weeks of evolution of the epidemic.

Method:

In an analytical cross-sectional design, the total number of cases of COVID-19 in Mexico from February 29 to July 24, 2020 was studied, and compared with sentinel cases calculated from the Rt. A descriptive and comparative analysis of prevalence, cumulative incidence and case fatality was performed to summarize the epidemiological data for Mexico and in relation to information for Italy, Spain, and the United States of North America.

Results:

In Mexico, until July 24, 2020, there are a total of 390,516 cases of COVID-19 and 43,680 deaths from this disease; with the use of Rt to calculate the correction of cases and unidentified deaths, the figure increases to 3,780,195 cases (p = 0.0002) and 211,469 deaths (p = 0.001). This suggests underreporting in the identification of cases and deaths and is associated with one of the highest case fatality rates in the world for SARS-CoV-2 infection.

Conclusions:

In Mexico, the sentinel model presents a significant loss of unquantified information. It is necessary to reinforce epidemiological surveillance through a better case detection strategy in our country and continue to apply measures that allow the containment and mitigation of the COVID-19 pandemic.

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