{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,10,13]],"date-time":"2026-10-13T06:20:33Z","timestamp":1791872433568,"version":"4.3.4"},"reference-count":28,"publisher":"MDPI AG","issue":"2","license":[{"start":{"date-parts":[[2026,2,22]],"date-time":"2026-02-22T00:00:00Z","timestamp":1771718400000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100007045","name":"Secretar\u00eda de Ciencias Humanidades, tecnolog\u00eda e Inovaci\u00f3n (SECIHTI) previously Consejo Nacional de Humanidades, Ciencia y Tecnolog\u00eda","doi-asserted-by":"publisher","award":["303081"],"award-info":[{"award-number":["303081"]}],"id":[{"id":"10.13039\/501100007045","id-type":"DOI","asserted-by":"publisher"}]},{"name":"Direcci\u00f3n General de Asuntos del Personal Acad\u00e9mico (DGAPA), Universidad Nacional Aut\u00f3noma de M\u00e9xico","award":["IN230423"],"award-info":[{"award-number":["IN230423"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Viruses"],"abstract":"<jats:p>Background: In 2019, pneumonia caused 740,180 deaths in children under five years of age, representing 22% of global mortality in this age group. During the COVID-19 pandemic, public health interventions markedly reduced the circulation of most respiratory viruses other than SARS-CoV-2, leading to significant post-pandemic shifts in respiratory pathogen epidemiology. This study aimed to characterize the epidemiology, clinical features, and risk factors associated with respiratory viruses and bacteria causing pneumonia in Mexican children during the late pandemic and post pandemic periods. Methods: Children younger than 14 years with pneumonia were recruited from seven hospitals in Mexico. Demographic and clinical data were collected, and nasopharyngeal swabs were analyzed using a multiplex PCR panel detecting 19 viruses and 7 bacteria. Univariate, bivariate, and logistic regression analyses were performed (SPSS v25). Results: A total of 1715 children were included: 704 during the pandemic (2021\u20132023) and 1011 post-pandemic (2023\u20132025). Co-infections (72% vs. 65%, p &lt; 0.001), virus\u2013virus co-infections (25% vs. 11%, p &lt; 0.001), and single viral infections (20% vs. 15%, p = 0.007) were more frequent during the pandemic. Pathogen detection was high in both periods, though negative samples increased post-pandemic (5.4% vs. 15%, p &lt; 0.001). During the pandemic, the 5 most frequently detected pathogens were rhinovirus (66%), RSV A and B (38%), Streptococcus pneumoniae (30%), Haemophilus influenzae (28%), human metapneumovirus (13%). In the post-pandemic period, the 5 most frequently detected pathogens were rhinovirus (52%), Haemophilus influenzae (36%), Streptococcus pneumoniae (35%), RSV A and B (28%), metapneumovirus (11%). Rhinovirus and RSV predominated during the pandemic, whereas Haemophilus influenzae, Streptococcus pneumoniae, parainfluenza viruses, Bordetella pertussis, and Mycoplasma pneumoniae significantly increased post-pandemic. Conclusions: Pediatric pneumonia epidemiology shifted from a predominantly viral profile during the pandemic to increased bacterial detections and virus\u2013bacteria co-infections post-pandemic, alongside re-emergence of typical RSV and influenza seasonality. Higher mean age and rhinovirus as the most frequent pathogen persist after the pandemic. Sustained molecular surveillance and reinforced vaccination programs remain essential in the post-pandemic era.<\/jats:p>","DOI":"10.3390\/v18020270","type":"journal-article","created":{"date-parts":[[2026,2,23]],"date-time":"2026-02-23T10:00:52Z","timestamp":1771840852000},"page":"270","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":3,"title":["Changes in the Epidemiology of Pneumonia in Children Younger than 14 Years Old During and After the COVID-19 Pandemic in Mexico, a National Multicenter Study"],"prefix":"10.3390","volume":"18","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-3582-5120","authenticated-orcid":false,"given":"Rosa Mar\u00eda","family":"Wong-Chew","sequence":"first","affiliation":[{"name":"Infectious Diseases Research Laboratory, Research Division, Facultad de Medicina, Universidad Nacional Aut\u00f3noma de M\u00e9xico (UNAM), Mexico City 04510, Mexico"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-1641-127X","authenticated-orcid":false,"given":"Patricia","family":"Bautista Carbajal","sequence":"additional","affiliation":[{"name":"Infectious Diseases Research Laboratory, Research Division, Facultad de Medicina, Universidad Nacional Aut\u00f3noma de M\u00e9xico (UNAM), Mexico City 04510, Mexico"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Ver\u00f3nica","family":"Tabla-Orozco","sequence":"additional","affiliation":[{"name":"Emergency Department, Hospital Pedi\u00e1trico de Coyoac\u00e1n, Mexico City 04000, Mexico"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0009-0003-1315-1246","authenticated-orcid":false,"given":"Mar\u00eda Del Carmen","family":"Espinosa-Sotero","sequence":"additional","affiliation":[{"name":"Department of Pediatrics, Hospital General de M\u00e9xico Dr. Eduardo Liceaga, Mexico City 06760, Mexico"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Pedro Antonio","family":"Mart\u00ednez-Arce","sequence":"additional","affiliation":[{"name":"Department of Pediatric Infectious Diseases, Antiguo Hospital Civil de Guadalajara Fray Antonio Alcalde, Guadalajara 44200, Mexico"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-4840-6742","authenticated-orcid":false,"given":"Daniel E.","family":"Noyola","sequence":"additional","affiliation":[{"name":"Center for Health Sciences and Biomedicine Research, Facultad de Medicina, Universidad Aut\u00f3noma de San Luis Potos\u00ed, San Luis Potos\u00ed 78210, Mexico"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Mar\u00eda Susana","family":"Ju\u00e1rez-Tob\u00edas","sequence":"additional","affiliation":[{"name":"Department of Pediatrics, Hospital Regional de Alta Especialidad Dr. Ignacio Morones Prieto, San Luis Potos\u00ed 78290, Mexico"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-7878-2503","authenticated-orcid":false,"given":"Gerardo","family":"Mart\u00ednez-Aguilar","sequence":"additional","affiliation":[{"name":"Hospital Municipal del Ni\u00f1o de Durango, Durango 34000, Mexico"},{"name":"Facultad de Medicina y Nutrici\u00f3n, Universidad Ju\u00e1rez del Estado de Durango, Durango 34076, Mexico"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-1744-9173","authenticated-orcid":false,"given":"Fabian","family":"Rojas-Larios","sequence":"additional","affiliation":[{"name":"Hospital Regional Universitario IMSS Bienestar de Colima, Colima 28000, Mexico"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Izveydi Zuyino","family":"Mondrag\u00f3n-Salinas","sequence":"additional","affiliation":[{"name":"Hospital de las Culturas, San Crist\u00f3bal de las Casas, Chiapas 29264, Mexico"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Miguel Leonardo","family":"Garc\u00eda-Le\u00f3n","sequence":"additional","affiliation":[{"name":"Infectious Diseases Research Laboratory, Research Division, Facultad de Medicina, Universidad Nacional Aut\u00f3noma de M\u00e9xico (UNAM), Mexico City 04510, Mexico"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2026,2,22]]},"reference":[{"key":"ref_1","unstructured":"(2025, December 24). 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Open"}],"container-title":["Viruses"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/1999-4915\/18\/2\/270\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2026,2,23]],"date-time":"2026-02-23T10:03:52Z","timestamp":1771841032000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/1999-4915\/18\/2\/270"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2026,2,22]]},"references-count":28,"journal-issue":{"issue":"2","published-online":{"date-parts":[[2026,2]]}},"alternative-id":["v18020270"],"URL":"https:\/\/doi.org\/10.3390\/v18020270","relation":{},"ISSN":["1999-4915"],"issn-type":[{"value":"1999-4915","type":"electronic"}],"subject":[],"published":{"date-parts":[[2026,2,22]]}}}