Background: Faced with the resurgence of malaria in the Peruvian Amazon since 2012, malaria surveillance was enhanced by adding a local active case detection (ACD) strategy to the routine passive case detection (PCD) as a reactive measure in selected communities with unusual number of cases during high transmission season (HTS). We assessed the short-effectiveness of this local ACD-based strategy in four Peruvian Amazonian riverine communities. Methods: A cohort study was conducted in June-July 2015 in Mazan, Loreto. Four consecutive ACD interventions (using light microscopy (LM) and treatment of confirmed infections) at intervals of 10 days were conducted in four riverine communities (Gamitanacocha-GAM, Primero de Enero-PRI, Libertad-LIB, and Urco Miraño-URC) that previously reported unusual number of cases. Blood samples were also collected on filter paper for later PCR. The effective...