Hidden Plasmodium falciparum infections

Mixed infection of P. vivax and P. falciparum malaria frequently recorded in field survey. However mixed infection was frequently misdiagnosed as single infection due to low parasite density, difficult species identification and procedure error of microscopic examination. Our previous report showed high rates (32-33%) of P vivax infection following treatment of previously assumed to be only P. falciparum infection. In a study of 992 patients with initial presentation with P. falciparum, we found that 104 (10.5%) of patients had P. falciparum appearing during 28 days in the hospital (ranged 1-28 days) following chloroquine treatment for P. vivax. The potential for P. falciparum appearing following elimination of P. vivax must be considered in malaria treatment.