New developments in Plasmodium vivax malaria: severe disease and the rise of chloroquine resistance.

PURPOSE OF REVIEW Unlike Plasmodium falciparum, Plasmodium vivax rarely causes severe disease in healthy travellers or in temperate endemic regions and has been regarded as readily treatable with chloroquine. However, in tropical areas, recent reports have highlighted severe and fatal disease associated with P. vivax infection. We review the evidence for severe disease and the spread of drug-resistant P. vivax and speculate how these maybe related. RECENT FINDINGS Studies from Indonesia, Papua New Guinea, Thailand and India have shown that 21-27% of patients with severe malaria have P. vivax monoinfection. The clinical spectrum of these cases is broad with an overall mortality of 0.8-1.6%. Major manifestations include severe anaemia and respiratory distress, with infants being particularly vulnerable. Most reports of severe and fatal vivax malaria come from endemic regions where populations have limited access to healthcare, a high prevalence of comorbidity and where drug-resistant P. vivax strains and partially effective primaquine regimens significantly undermine the radical cure and control of this relapsing infection. The mechanisms underlying severe disease in vivax malaria remain poorly defined. SUMMARY Severe, fatal and multidrug-resistant vivax malaria challenge our perception of P. vivax as a benign disease. Strategies to understand and address these phenomena are needed urgently if the global elimination of malaria is to succeed.