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

BACKGROUND: Seasonal 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. METHODS: We 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. RESULTS: During 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). CONCLUSION: The 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. [Image: see text] [Image: see text] [Image: see text] DISCLOSURES: All authors: No reported disclosures.