Polymerase chain reaction fails to detect mixed malaria infections in siblings from Ethiopia.

Malaria remains a significant public health concern in sub-Saharan Africa, particularly in Ethiopia where Plasmodium falciparum and Plasmodium vivax are co-endemic. Most cases in the United States are acquired abroad and imported. Peripheral blood smears remain the gold standard of diagnosis, but their relatively low sensitivity and reliance on skilled interpretation have led to the growing use of polymerase chain reaction (PCR)-based diagnostics. We report cases of malaria in two pediatric siblings who had recently returned from Ethiopia, where PCR initially failed to detect P. vivax. Recurrent symptoms eventually led to diagnosis of P. falciparum/P. vivax co-infection by PCR and blood smear. This case highlights the limitations of current malaria diagnostics, which may fail to detect mixed infections and lead to delayed or incomplete treatment. Clinicians should maintain a high index of suspicion for malaria in patients returning from co-endemic regions, as mixed infections may emerge after a prolonged period without re-exposure to an endemic area.