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

Abstract 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.