Malaria due to infection with P. vivax is currently estimated at up to 390 million episodes per year worldwide, with substantial morbidity caused by the recurrent nature of its infection, associated anaemia and adverse effects on pregnancy, and ability to cause severe disease and death. The majority of malaria cases from all Plasmodium species in Malaysia are from the Eastern state of Sabah, where despite around a 36-fold reduction in incidence since the implementation of malaria eradication programs in 1961, minimum estimates based on unpublished microscopy data from Sabah State public health records still detailed 8685 malaria cases in 2009-2011. While P. vivax accounts for between 30-50% of these figures currently, studies have demonstrated as overall transmission rates in countries previously endemic for malaria decline the proportion of cases attributable to P. vivax increases. Mixed P. falciparum / P. vivax infections are also likely to be underestimated in areas of co-endemicity, with high rates of recurrence of P. vivax shown in studies following treatment for apparent P. falciparum mono-infection or mixed Plasmodium spp. infections.