The study by Cox-Singh et al. investigates the geographic distribution and clinical impact of *Plasmodium knowlesi* malaria in humans in Malaysia. *P. knowlesi* was previously misdiagnosed as *P. malariae*, leading to underestimation of its prevalence and severity. The researchers used sensitive nested PCR to analyze blood samples from 960 malaria patients in Sarawak, 49 archival blood films from Sabah, and 5 from Pahang. They found *P. knowlesi* DNA in 266 (27.7%) of Sarawak samples, 41 (83.7%) of Sabah samples, and all 5 Pahang samples. Four fatal cases of *P. knowlesi* malaria were also identified, all of which were hyperparasitemic and presented with severe hepatorenal dysfunction. The study highlights the widespread distribution of *P. knowlesi* in Malaysian Borneo and the need for rapid diagnosis and prompt treatment to prevent severe complications. The authors recommend that patients with hyperparasitemia and parasite morphology resembling *P. malariae* be diagnosed as *P. knowlesi* to improve clinical management and control strategies.The study by Cox-Singh et al. investigates the geographic distribution and clinical impact of *Plasmodium knowlesi* malaria in humans in Malaysia. *P. knowlesi* was previously misdiagnosed as *P. malariae*, leading to underestimation of its prevalence and severity. The researchers used sensitive nested PCR to analyze blood samples from 960 malaria patients in Sarawak, 49 archival blood films from Sabah, and 5 from Pahang. They found *P. knowlesi* DNA in 266 (27.7%) of Sarawak samples, 41 (83.7%) of Sabah samples, and all 5 Pahang samples. Four fatal cases of *P. knowlesi* malaria were also identified, all of which were hyperparasitemic and presented with severe hepatorenal dysfunction. The study highlights the widespread distribution of *P. knowlesi* in Malaysian Borneo and the need for rapid diagnosis and prompt treatment to prevent severe complications. The authors recommend that patients with hyperparasitemia and parasite morphology resembling *P. malariae* be diagnosed as *P. knowlesi* to improve clinical management and control strategies.