In Brazil, in 1903, the young physician Carlos Chagas (most known for the discovery of American trypanosomiasis afterwards) wrote his MD thesis on the haematological complications of malaria, which, at that moment, also occurred in the non-Amazon area. His major findings in studying P. vivax patients were severe anaemia, splenomegaly, leukopenia, cachexia and jaundice associated to concomitant staphylococcal disease [22] . Bone marrows were also analysed in these patients with no conclusive findings. Later on, during the 1940s, Djalma Batista in Manaus described a series of malarial cases from his outpatient clinics in whom large splenomegaly, cachexia and minor bleeding were frequent among those with the 'benign' tertian malaria [23] . More recently, from 1998 to 2008, 234 deaths related to vivax disease were officially reported to the Brazilian Ministry of Health [18] , and an increase in the hospitalization trends for vivax patients was published in a tertiary care hospital from Manaus [24] . To complicate matters, these facts parallel a lack of robust biomarkers and specific criteria for severe disease for this species in the literature. A sine qua non requisite in the analysis of clinical severity related to P. vivax infection is the exclusion of mixed infection with P. falciparum through a more sensitive technique such as PCR and the exclusion of other co-morbidities which may be responsible for the clinical presentation per se. In the literature, in general, reports of 'complicated/severe' cases lack more precise and uniform definition criteria, in part due to the rare application of more robust endpoints such as death and admission to the intensive care unit (ICU), and therefore end up suffering bias through individual judgment of authors, editors and reviewers. As in most of the data published there were no systematic exclusion of co-morbidities and/or mono-infection confirmation using PCR, performing a meta-analysis of severe manifestations of P. vivax becomes virtually impossible. The other bias in the case of Brazil is that many relevant data are confined in abstracts from national scientific meetings and graduate students' dissertations and theses. The systematic review of these unpublished data therefore could contribute to the understanding of the clinical spectrum of vivax infection in this country and ultimately as a representative sample from Latin American vivax malaria.