Loreto, covering 28% of Peru's territory with around one million inhabitants, is the department most affected by malaria. In 2017, it reported 53163 malaria cases (about 90% of total cases in the country), of which 75% and 25% were caused by P. vivax and P. falciparum, respectively. Recent reports in South-American co-endemic countries for both species indicated that severe malaria (SM) caused by P. vivax is not rare.

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...