SARS-CoV-2 variants and associated cases during four epidemic waves in Sinaloa, Mexico

Abstract

The COVID-19 pandemic is a global public health problem that has revealed deficiencies and challenges in health systems worldwide. To date, four waves (each one driven by different viral variants and showing different behaviors) have affected Mexico. Here we describe the COVID-19 pandemic behavior in the population of Sinaloa, Mexico after four epidemic waves. Epidemiological data were obtained from public federal databases from March 2020 to February 2022, and genomes of SARS-CoV-2 variants of interest (VOI) and concern (VOC) in Sinaloa were downloaded from the GISAID database from January 2021 to May 2022. The relative risk (RR) of SARS-CoV-2 infection was calculated from public data. Sinaloa presented four epidemic waves from March 2020 to February 2022, and each wave was driven by different variants with different degrees of transmissibility and severity. Interestingly, the delta variant (which dominated the third wave) was probably the most severe, producing a large number of cases per day and high mortality rates, while the omicron variant (which dominated the fourth wave) produced the largest number of cases per day but decreased mortality rates. Most of the COVID-19 cases in Sinaloa occurred among people between 30 and 45 years old, and the average age of the deceased was above 60 years old in all waves. Older people showed higher risk of infection than infants and younger people; however, the relative risk (RR) for people older than 60 years old decreased in the third and fourth waves. Men older than 60 years old showed higher RR than women of the same age group. The COVID-19 pandemic has shown changing behaviors in time, mostly derived from different emerging viral variants and the immunization of the population. Overall, these results show that SARS-CoV-2 infections appear in timely waves, each one driven by different variants (and subvariants or sublineages), with different degrees of transmissibility and severity. The population should continue with preventive measures to avoid infection.