To describe epidemiology, seasonality, burden and identify new viral strains of influenza in Tanzania, in 2008 the country initiated the National Influenza Surveillance System.This study aimed at assessingthe distribution, trend and associated demographic factors for influenza cases in Tanzania from 2016 to 2019. Methodology: Was a cross-sectional study using secondary data obtained from national laboratory information systemat National Influenza Center (NIC) dataset from 2016 to 2019. Results: A total of 7260 swab samples were collected between 2016 to 2019 from clients with a median age of 4 years [Interquartile range (IQR) =25; (26,1)], most samples (53.4%) were from patients aged under five years. From the samples collected,58% (4137/7171) were from Influenza-Like Illness (ILI) clients while 42% (3034/7171) were from those who hadSevere Acute Respiratory Illness (SARI).Laboratory confirmation was done by PCR technique whereby cases were 17% with a higher prevalence of influenza A [12% (881/7260)] as compared to influenza B [5% (373/7260)].Sixty seven percent(844/1254) of positive samples were from patients enrolled with ILI. We observed the seasonality of influenza withincreased cases in rainy and cold seasons.Individuals with SARI had 25% less likelihood of testing positive for Influenza as compared to those presenting with ILI"(aOR 0.75, 95% CI [0.64-0.89], p=0.001). Conclusion: Children aged under five years, being the most affected group, requires nonstop support and care.ILI cases need attention in care and management,having known the seasonality of the disease apprises for the proper allocation of resources for the surveillance activities.

Keywords : Influenza, Sentinel surveillance, Severe acute respiratory infections, Influenza like illness, National public health laboratory, National influenza center.