1667. Influenza A and B Co-Circulation and Burden: A 2018–2019 Influenza Season Analysis Using the National Active Surveillance Database in Mexico

Abstract

BackgroundSeasonal influenza is a prevalent respiratory infection for children and adults in Mexico. Influenza A and B viruses co-circulate and there is a need to better understand local epidemiology to inform vaccination recommendations (tri- vs. quadrivalent vaccines). We describe the 2018–2019 influenza season to estimate influenza burden, virus co-circulation and understand the vaccine match in Mexico.MethodsWe reviewed preliminary sentinel surveillance data for the influenza season (October 2018–May 2019) from the Mexican Health Secretariat and World Health Organization’s (WHO) FluNet databases. We performed a descriptive analysis of cases and deaths due to influenza-like illness (ILI), severe acute respiratory infections (SARI) and lab-confirmed influenza to estimate the prevalence of influenza A and B circulating strains, per state and age group, and determine B strain vaccine match.ResultsDuring the 2018–2019 season in Mexico, there were 52,525 reported cases of ILI/SARI with 6,997 lab-confirmed influenza cases (28% positivity rate among ILI/SARI) and 787 (11%) deaths (Figures 1 and 2). The states with 36% of cases were Mexico City, State of Mexico, Hidalgo, Tlaxcala, and Guanajuato. More than half of the Mexican states had a high (10–14.9%) to intense (≥15%) accumulated case positivity rate of confirmed influenza in relation to ILI/SARI cases (Figure 3). Most cases were reported among the 1–9 and > 60-year-old groups. 45% of deaths occurred in State of Mexico, Hidalgo, Mexico City, Puebla, and Guanajuato. The seasonal viral profile was dominated by A/H1N1 (68%), followed by B (16%) and A/H3N2 (12%), with 90% of deaths attributed to A/H1N1. FluNet’s influenza B data show Yamagata (55%) and Victoria (27%) co-circulation (Figure 1).ConclusionThe 2018–2019 seasonal co-circulation of influenza A and B viruses in Mexico showed significant nation-wide morbi-mortality burden, with A/H1N1 and B/Yamagata dominance. Stronger B lineage determination is needed in Mexico to understand associated burden and prevent vaccine mismatch, considering the trivalent vaccine does not contain both B strains. Given the circulation of both influenza B lineages and the recommendation of the WHO, Mexico could enhance quadrivalent vaccine use in coming seasons to optimize protection. Disclosures All authors: No reported disclosures.