spread of ATL, but we were unable to extrapolate findings from animal models to human disease. http://dx.Background: Muleba is one of the malaria sentinel sites in a country. It is known to have several malaria outbreaks. The first outbreak occurred in 1997 with a case fatality ratio (CFR) of 3.7% and the second was in 2006, with CFR of 2.8%. On the 1 st of June 2013, the Ministry received report of 123 cases with CFR of 7.3%, an increase in the number of admitted < 5 malaria cases from Muleba district. Tanzania FELTP conducted an investigation to confirm the existence of the outbreak, determine attributing factors and institute control measures. Methods & Materials:We reviewed the weekly line list and medical records of admitted patients from the 1 st epidemiology week of calendar year 2013 and interviewed 302 admitted feverpatients, parent, or care taker on bed net ownership and usage. Data was abstracted using a structured data collection check list. A total of 38 samples were taken for further investigations to rule out borrelia, yellow fever and dengue viral infection. Data was analysed using Microsoft Excel and Epi Info version 3.5.4Results: From 9 th -23 rd Epidemiology week, there were a total of 2,366 cases and 131 deaths (CFR = 5.5%); 86 (65.6%) due to malaria with majority 71 (82.6%) being < 5.A total of 302 fever admitted cases were interviewed; out of 184 tested for malaria, 149 (81%) were positive. Majority 258 (85.4%) came from villages that were uncovered by Indoor Residual Spraying (IRS) intervention. About 179 (59.3%) reported to own mosquito bed nets. Majority 233 (77.2%) delayed seeking medical care and sought traditional herbs.Of the 38 blood samples taken for analysis at the National Laboratory (NHL-QATC), 21 (55.3%) tested positive for malaria and all were negative for borrelia, dengue and yellow fever.Conclusion: An outbreak ofmalaria was confirmed. Factors contributing to high CFR included late medical seeking behaviour, use of traditional herbs at home, poor bed net usage and lack of IRS intervention activities. There is a need to sensitize communities on early medical seeking behaviour and revitalizing other malaria control initiatives like IRS. Other causes of fever other than malaria should also be explored.http://dx.