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Date of this Version



Annals of TropicalMedicine & Parasitology, Vol. 97, No. 6, 565–574 (2003)


U.S. Government Work


The clinical and parasitological characteristics of the .rst naturally acquired malarial infection have rarely been documented in humans. When 243 migrants from non-endemic Java were followed from the day of their arrival in Indonesian Papua, 217 (89%) were found to become infected with Plasmodium falciparum and/or P. vivax before they were lost to follow-up. The incidence of malarial infection in the children investigated (who were aged 6–10 years) was indistinguishable from that in the adults (aged >20 years), with 1.10 and 1.14 P. falciparum infections/person-year (relative risk=0.97; 95% con.dence interval=0.72–1.29) and 1.47 and 1.49 P. vivax infections/person-year (relative risk=0.99; 95% con.dence interval=0.72–1.29), respectively. During their first infections, the children had higher P. falciparum parasitaemias than the adults (with geometric means of 1318 and 759 parasites/ml, respectively; P=0.04) but similar P. vivax parasitaemias (with geometric means of 355 and 331 parasites/ml, respectively; P=0.76). At .rst infection, 56% of the subjects were febrile and 90% complained of symptoms. There were no diVerences between children and adults with respect to these two parameters, either for P. falciparum or P. vivax. These .ndings indicate that, with promptly diagnosed and treated uncomplicated malaria, migrant children and adults in north–eastern Indonesian Papua have an equal risk of malarial infection and of disease following their .rst infections with P. falciparum and P. vivax.