Influenza in Yucatan in 2018: Chronology, characteristics and outcomes of ambulatory and hospitalized patients

Introduction: Influenza season is expected between October and February in the northern hemisphere, including Mexico. Previous studies suggested that transmission peak may occur earlier in Yucatan, a state in southeast Mexico. Objectives: (a) Describe the seasonality of 2018 influenza cases seen at O´Horan hospital, statewide, and nationwide; (b) analyze the characteristics, clinical manifestations and outcomes of ambulatory and hospitalized patients; (c) analyze fatal outcomes occurrence among vaccinated and unvaccinated individuals. Methods: Retrospective analytic cohort of all confirmed influenza cases assisted at O´Horan hospital during 2018, along with a chronologic graphic description of the statewide epidemic curve from the epidemiological surveillance registries. Results: A total of 264 influenza cases were analyzed; 145 (55%) were female; 26% were vaccinated. Health workers and unvaccinated individuals were more prone to develop severe cases. Dyspnea and tachypnea were strong predictors of hospitalization; headache, myalgias, arthralgias and rhinorrhea correlated inversely. 236 (89.47%) cases occurred in July and 22 of the 23 deaths occurred before October. No fatal outcomes were observed among vaccinated individuals. Influenza AH1N1 represented 83.6% of serotyped cases. Discussion: Onset of influenza season in Yucatan may reflect a need for rethinking timing of vaccination and of preventive campaigns, as most cases occurred before vaccination period. Keywords: Influenza virus, Infection, Hospitalization, Signs and symptoms