Reemerging Influenza Virus Infections during the Dominance of the Omicron SARS-CoV-2 Variant in Mexico

Mónica Ríos-Silva; Xóchitl Trujillo; Miguel Huerta; Verónica Benites-Godínez; José Guzmán-Esquivel; Jaime Alberto Bricio-Barrios; Oliver Mendoza-Cano; Agustín Lugo-Radillo; Efrén Murillo-Zamora

doi:10.3390/pathogens11101181

Reemerging Influenza Virus Infections during the Dominance of the Omicron SARS-CoV-2 Variant in Mexico

Pathogens. 2022 Oct 13;11(10):1181. doi: 10.3390/pathogens11101181.

Affiliations

¹ University Center for Biomedical Research, CONACyT-University of Colima, Av. 25 de Julio 965, Col. Villas San Sebastián, Colima 28045, Mexico.
² University Center for Biomedical Research, University of Colima, Av. 25 de Julio 965, Col. Villas San Sebastián, Colima 28045, Mexico.
³ Health Education Coordination, Mexican Institute of Social Security, Calzada del Ejercito Nacional 14, Col. Fray Junípero Serra, Tepic 63160, Mexico.
⁴ Academic Unit of Medicine, Autonomous University of Nayarit, Ciudad de la Cultura Amado Nervo, Tepic 63155, Mexico.
⁵ Faculty of Medicine, University of Colima, Av. Universidad 333, Col. Las Víboras, Colima 28040, Mexico.
⁶ Clinical Epidemiology Research Unit, Mexican Institute of Social Security Institute, Instituto Mexicano del Seguro Social, Av. Lapislázuli 250, Col. El Haya, Villa de Álvarez 28984, Mexico.
⁷ Faculty of Civil Engineering, University of Colima, km. 9 carr. Colima-Coquimatlán, Coquimatlán 28400, Mexico.
⁸ Faculty of Medicine and Surgery, CONACyT-Autonomous University Benito Juarez of Oaxaca, Ex Hacienda Aguilera S/N Sur, camino a San Felupe del Agua, Oaxaca 68020, Mexico.
⁹ Family Medicine Unit No. 19, Department of Epidemiology, Mexican Institute of Social Security, Av. Javier Mina 301, Col. Centro, Colima 28000, Mexico.

Abstract

The burden of influenza in Mexico has been high. We aimed to characterize its epidemiological patterns before and during the coronavirus disease 2019 (COVID-19) pandemic. A retrospective cohort study was conducted and 5652 PCR-confirmed cases of influenza (October 2019-April 2022) were analyzed. The highest incidence (144 per million) was observed in December 2019 and rapidly decreased right before the start of the pandemic (February 2020). No cases were documented in the 2020-2021 season, and infections reemerged at a low level (8 per million) in December 2021. The case-fatality rates were around 5% in both seasons (p = 0.591). The dominant strains were AH1N1 and AH3N2 in the 2019-2020 and 2021-2022 seasons, respectively. In multiple analysis, males and older patients were at increased risk of a fatal outcome. Flu vaccination and infection by B lineages (vs. AH1N1) showed a protective effect. Our results suggest that the spread of the influenza virus reemerged in the 2021-2022 season when the SARS-CoV-2 Omicron variant (B.1.1.529) was dominant. Efforts focusing on the prevention of transmission of respiratory viral pathogens, together with flu vaccination, may be useful to reduce the risk of an influenza outbreak.

Keywords: COVID-19; SARS-CoV-2 variants; human; incidence; influenza.

Grants and funding

This research received no external funding.