Since the 2023-2024 winter season, Mexico has changed its approach to respiratory virus epidemiological surveillance, shifting from universal surveillance to sentinel surveillance. Confirmation of SARS-CoV-2 is now exclusively through virus identification using reverse transcription polymerase chain reaction (RT-PCR). The Ministry of Health's report for epidemiological week 53 of 2024 highlights that newly confirmed cases have decreased over the past five years, making it necessary to consider this trend when asserting a downward trend. However, a comparison between 2025 and 2024 reveals a preliminary 49% decrease. Despite being a viral respiratory illness, the highest positivity rate for SARS-CoV-2 in 2025 was identified during epidemiological weeks 12 to 30, while the lowest positivity rates were recorded during the first and last weeks of the year. (1) Recently, the Pan American Health Organization issued an epidemiological alert in January 2026 regarding the simultaneous circulation of seasonal influenza and respiratory syncytial virus in the Americas region (Canada and the United States of America). (2) Regarding genomic surveillance, the health authority report shows information up to June 2025, where the most prevalent variant of interest during the year was LP.8.1. However, the information available in GISAID for Mexico, covering January to September 2025, reveals the circulation of multiple variants, with varying predominance throughout the year; in January, 40% were XEC and JN.1 in 33%, by March the change was observed with LP.8.1 predominating in 60% of the samples and XGF in 90% in September 2025 (3). This demonstrates the decreasing relevance of genomic surveillance of the virus in the country. Silva and colleagues published findings highlighting the effectiveness of wastewater-based epidemiology as a viable tool for monitoring community-level SARS-CoV-2 infection trends in Mexico City during 2021 and 2022 (4).

While sentinel surveillance had proven effective in Mexico prior to the COVID-19 pandemic (5-8), the first case of human infection with avian influenza A(H5N1) in a tertiary care hospital of the Mexican Social Security Institute (9) underscored the importance of surveillance outside of sentinel units. Therefore, it is essential to maintain epidemiological surveillance of respiratory viruses in Mexico's medical facilities to enable timely detection, monitor circulation, assess severity, and guide the response to acute respiratory infections.

1.Dirección General de Epidemiología. Informe semanal. Situación epidemiológica de la COVID-19, influenza y otros virus respiratorios. Semana epidemiológica No. 53 de 2025. Available at: https://www.gob.mx/salud/documentos/informes-semanales-para-la-vigilancia-epidemiologica-de-influenza-covid-19-y-otros-virus-respiratorios-2025

2.Organización Panamericana de la Salud. Alerta Epidemiológica Circulación simultánea de influenza estacional y virus sincitial respiratorio (VSR) 9 de enero del 2026. Available at: https://www.paho.org/es/documentos/alerta-epidemiologica-circulacion-simultanea-influenza-estacional-virus-sincitial

3.GISAID. hCoV-19 (SARS-CoV-2) Variants and Lineages. Mexico. Available at: https://gisaid.org/hcov-19-variants-dashboard/

4.Silva-Magaña MA, Mazari-Hiriart M, Noyola A, Espinosa-García AC, de Anda-Jáuregui G, Hernández-Lemus E. Temporal dynamics of SARS-CoV-2 detection in wastewater and population infection trends in Mexico City. Front Public Health. 2025 Aug 14;13:1640581. Doi: 10.3389/fpubh.2025.1640581.

5.Ruiz-Matus C, Kuri-Morales P, Narro-Robles J. Comportamiento de las temporadas de influenza en México de 2010 a 2016, análisis y prospectiva [Behavior of influenza seasons in Mexico from 2010 to 2016: Analysis and prospective]. Gac Med Mex. 2017 Mar-Apr;153(2):205-213. Spanish.

6.Cabrera-Gaytán DA, Grajales-Muñiz C, Rojas-Mendoza T, Arriaga-Nieto L, Vallejos-Parás A. La vigilancia epidemiológica en el IMSS: un recuento de los éxitos institucionales. Rev Med Inst Mex Seguro Soc [Internet]. 2025 May 1 [cited 2026 Jan. 14];63(3):e6551. Available from: https://revistamedica.imss.gob.mx/index.php/revista_medica/article/view/6551

7.Echevarría-Zuno S, Mejía-Aranguré JM, Mar-Obeso AJ, Grajales-Muñiz C, Robles-Pérez E, González-León M, Ortega-Alvarez MC, Gonzalez-Bonilla C, Rascón-Pacheco RA, Borja-Aburto VH. Infection and death from influenza A H1N1 virus in Mexico: a retrospective analysis. Lancet. 2009 Dec 19;374(9707):2072-2079. Doi: 10.1016/S0140-6736(09)61638-X. Epub 2009 Nov 11.

8.Borja Aburto VH, Grajales Muñiz C, González León M, Mejía Arangure JM. Estimación de la incidencia de influenza pandémica A(H1N1) 2009 en derechohabientes del Instituto Mexicano del Seguro Social. Gaceta Médica de México. 2011;147:303-10.

9.World Health Organization. Avian Influenza A(H5N1) – Mexico. 17 April 2025. Available at: https://www.who.int/emergencies/disease-outbreak-news/item/2025-DON564