The importance of being vivax.

Plasmodium vivax is indisputably the most widely distributed cause of human malaria, and the prevailing species outside of Sub-Saharan Africa [1], putting over one-third (2.5 billion people) of the globe's population [2] at risk every year, and causing an estimated 80–300 million annual clinical episodes [3]. Plasmodium vivax is heterogeneously scattered in the different continents, with over 80% of the total global burden unevenly circumscribed to the Pacific and central and southeast Asia [1, 2]. In America, the total burden is significantly lower, but this species still causes over 70% of all malaria episodes. In Africa, the high prevalence of the Duffy-negative genotype (inherently associated with a refractoriety to P. vivax invasion, and thus the major genetic determinant of its distribution [4]) has traditionally contained the dissemination of this species which is only frequently described in some areas of the horn of Africa and the Madagascar island, despite increasing reports of its circulation and transmission across the continent [5, 6]. Despite such robust evidence on this parasite's burden and impact, efforts devoted in the past decades to the understanding and control of P. vivax have been meagre, particularly in comparison with those made for its sibling species Plasmodium falcip-arum, the major cause of malaria-related deaths globally. A review of funds invested for malaria research from 2007 to 2009 confirmed that a mere 3.1% of all funding had specifically targeted P. vivax [7], and the imbalance in publications or bibliographical references addressing either of the two parasite species is equally astonishing (Fig. 1). However, the past decade has witnessed an important paradigm change regarding these disparities. Indeed, the scientific and global health communities appear to be slowly confronting the significant neglect suffered by this malaria species and are increasingly devoting more attention and funds to P. vivax research and control. Several reasons may explain the recent and unexpected focus on P. vivax. First, increasing reports of severe or even life-threatening episodes involving P. vivax infections [8–10] have modified this para-site's dogmatic 'benign' consideration [11]. Indeed, most malaria-endemic areas in which this parasite is transmitted have now confirmed that it can cause severe disease, on its own, as a mixed infection in combination with P. falciparum or as a triggering factor of complications in patients with other co-infections or underlying co-morbidities [12]. Our current capacity, through the use of molecular tools, to pick up vivax monoinfections and rule out coexisting falciparum infections …