Background Influenza is one of the most common viral respiratory diseases in the United States with 9–45 million cases per year. In Puerto Rico, more than 18,000 cases of influenza were reported during the 2019/20 season. The Sentinel Enhanced Dengue Surveillance System (SEDSS) conducts acute febrile illness surveillance for inpatient and outpatients at a southern Puerto Rico tertiary care hospital. Methods We performed a retrospective analysis of disease severity among laboratory-confirmed influenza cases enrolled in SEDSS. Cases with complications such as pneumonia or bronchitis evidenced by chest x-ray or clinical diagnosis were classified as severe. Results Between January 2016 and December 2019, there were 2,835 laboratory-confirmed influenza cases. More than half (1,662, 59%) were aged 0–20 years, 51% (n=1,447)were female, and 4% (n=124)required hospital admission. Among all influenza cases, influenza A virus was most common (n = 1,963, 69%) followed by influenza B virus (n = 872, 31%). Odds of having influenza A were higher among adults (OR=1.62; 95% CI:1.38-1.92). Chronic disease history among influenza cases included: asthma (n= 507, 18%), hypertension (n = 337, 12%), hypercholesterolemia (n = 157, 6%), coronary heart disease (n = 79, 3%), immunodeficiency (n = 11, 1%), and kidney disease (n = 10, 1%). Overall, 61(2%) influenza cases developed complications, 21 developed pneumonia of which 85% had chest x-ray performed. One-third of influenza cases with pneumonia or bronchitis had preexisting conditions like asthma (33%) and hypertension (34%). Seventy five percent of Influenza A cases with asthma developed bronchitis or pneumonia. The odds of having severe Influenza were higher among patients with underlying hypertension compared to those without hypertension (OR= 3.8; 95% CI:2.0–7.1). Moreover, influenza cases with asthma had a higher odd of developing pneumonia or bronchitis as compared to those without asthma (OR=2.3; 95% CI: 1.3–4.0). While asthma is a recognized risk factor for influenza complications, isolated hypertension is not. Conclusion Identifying people at risk for influenza complications provides a guide for clinicians and public health officials to implement preventive measures and improve clinical outcomes. Disclosures All Authors: No reported disclosures