Although not associated with the most severe form of falciparum malaria, Plasmodium vivax is the most common cause of malaria in humans and is responsible for 70-80 million clinical cases annually. Vivax malaria is a re-emerging disease for which 2.6 billion people are at risk. In Brazil it is responsible for 80% of malaria cases. Unlike P. falciparum it has no var homologues, but considerable sequence variation is found among SERA gene homologues.