Molecular Epidemiology of Noroviruses In Mexico: Challenges and Inclusion in Global Surveillance-The Role of NoroSurv.

Fabian Gomez, Instituto de Diagnóstico y Referencia Epidemiológicos

1) Fabián Gómez-Santiago, Instituto de Diagnóstico y Referencia Epidemiológicos. 2) Sergio Isaac de la Cruz-Hernández, Instituto de Diagnóstico y Referencia Epidemiológicos. 3) Yazmin Anaya-Molina, Instituto de Diagnóstico y Referencia Epidemiológicos. 4) Atenea Andrés-Dionicio, Instituto de Diagnóstico y Referencia Epidemiológicos. 5) Heidi Terán-Vega, Instituto de Diagnóstico y Referencia Epidemiológicos. 6) Héctor Méndez-Pérez, Instituto de Diagnóstico y Referencia Epidemiológicos. 7) Angelina Aguilar Guzmán, Instituto de Diagnóstico y Referencia Epidemiológicos. 8) Izmir Morales Báez, Escuela Nacional de Ciencias Biológicas, IPN.

Epidemology

Globally, noroviruses remain one of the leading causes of acute gastroenteritis across all age groups, likely due to their high genetic variability, the absence of a norovirus vaccine and the possible positive evolutionary selection pressure exerted by the rotavirus vaccine and other immunization efforts. Between 2014 and 2024, the Gastrointestinal Virus Laboratory at InDRE reported national norovirus positivity rates ranging from 12.55% to 27.52%, highlighting its consistent prevalence over these years. Stool samples (n=685) were collected as a part of the Public Health Laboratories National Network surveillance during 2024. From these, 86 positive noroviruses specimens were genotyped by RT-PCR. Thereafter, sequencing of 17 selected norovirus strains was performed in order to determine its genetic lineage. Our RT-PCR results revealed that the GII genogroup was the most prevalent, accounting for 91.86% (79/86) of detected cases, followed by the GI genogroup at 8.14% (7/86). Phylogenetic analysis of partial sequencing of the RdRP/VP1 gene conjunction—performed using the online tool available in NoroSurv—identified for the first time, two predominant RdRP sublineages: GII.P31 and GII.P16, and two VP1 sublineages of norovirus strains, GII.4 San Francisco and GII.4 Sydney. Together have been circulating throughout 2024 and may soon emerge as the dominant human norovirus genotypes in the country. These findings highlight the need to increase the amount of genetic information with the NoroSurv platform, carry out national meticulous surveillance of circulating and emerging strains to detect uncommon or novel variants of norovirus strains and evaluate their potential impact on a possible norovirus vaccine efficacy.