Comparable severity of Plasmodium vivax and Plasmodium falciparum malaria in hospitalized patients in the Peruvian Amazon.
Plasmodium vivax malaria has long been considered less severe than P. falciparum infection. However, there is growing evidence that P. vivax can lead to severe and life-threatening disease, although its burden is likely to be underestimated, particularly in low-transmission settings.This study aimed to contextualize the application of World Health Organization (WHO) severe malaria criteria in a low-transmission setting by describing the clinical and parasitological profile of hospitalized malaria patients in the Peruvian Amazon.
We conducted a retrospective hospital-based study at Hospital Regional de Loreto, Iquitos, Peru, from January 1, 2023, to October 30, 2025. The total hospital malaria caseload was determined from records assigned a laboratory-confirmed ICD-10 malaria diagnosis. The analytic cohort comprised hospitalized patients with microscopy-confirmed malaria who received intravenous artesunate because of severe malaria according to the WHO 2022 criteria, or inability to tolerate oral antimalarial treatment.
During the study period, 519 laboratory-confirmed malaria diagnoses were recorded in the hospital; of these, 127 patients (24.5%) were hospitalized. Of these, 97 had P. vivax infection (76.4%), 27 had P. falciparum infection (21.3%), 2 had mixed P. vivax/P. falciparum infection (1.6%), and 1 had P. malariae infection (0.8%). Overall, 67 patients (52.8%) met criteria for severe malaria, which was observed in 51/97 patients with P. vivax (52.6%) and 14/27 patients with P. falciparum (51.9%), with no significant difference between species. Notably, patients with P. vivax malaria presented with severe manifestations including impaired consciousness, pulmonary oedema or acute respiratory distress syndrome, and shock. Laboratory differences between species were modest, although P. falciparum infections were associated with lower haemoglobin and glucose levels, while P. vivax was associated with more marked thrombocytopenia. Clinical outcomes were generally favourable, with one death to which malaria-related complications may have contributed.
P. vivax contributed substantially to severe malaria in this low-transmission Amazonian setting and showed a severity profile similar to that of P. falciparum. The overlap observed between severe and non-severe presentations supports the contextual application of international severity criteria and continued recognition of the clinically important burden of P. vivax malaria.
We conducted a retrospective hospital-based study at Hospital Regional de Loreto, Iquitos, Peru, from January 1, 2023, to October 30, 2025. The total hospital malaria caseload was determined from records assigned a laboratory-confirmed ICD-10 malaria diagnosis. The analytic cohort comprised hospitalized patients with microscopy-confirmed malaria who received intravenous artesunate because of severe malaria according to the WHO 2022 criteria, or inability to tolerate oral antimalarial treatment.
During the study period, 519 laboratory-confirmed malaria diagnoses were recorded in the hospital; of these, 127 patients (24.5%) were hospitalized. Of these, 97 had P. vivax infection (76.4%), 27 had P. falciparum infection (21.3%), 2 had mixed P. vivax/P. falciparum infection (1.6%), and 1 had P. malariae infection (0.8%). Overall, 67 patients (52.8%) met criteria for severe malaria, which was observed in 51/97 patients with P. vivax (52.6%) and 14/27 patients with P. falciparum (51.9%), with no significant difference between species. Notably, patients with P. vivax malaria presented with severe manifestations including impaired consciousness, pulmonary oedema or acute respiratory distress syndrome, and shock. Laboratory differences between species were modest, although P. falciparum infections were associated with lower haemoglobin and glucose levels, while P. vivax was associated with more marked thrombocytopenia. Clinical outcomes were generally favourable, with one death to which malaria-related complications may have contributed.
P. vivax contributed substantially to severe malaria in this low-transmission Amazonian setting and showed a severity profile similar to that of P. falciparum. The overlap observed between severe and non-severe presentations supports the contextual application of international severity criteria and continued recognition of the clinically important burden of P. vivax malaria.
Authors
Bresciani Bresciani, Guardiani Guardiani, Rojas-Blasquez Rojas-Blasquez, Ramirez Ramirez, Iaquinandi Iaquinandi, Martel Martel, Velarde-Mera Velarde-Mera, Sifuentes-Vidigal Sifuentes-Vidigal, Carraro Carraro, Russo Russo, Pasquazzi Pasquazzi, Celis Celis, Casapia Morales Casapia Morales, Nicastri Nicastri, Asayag Asayag, Lichtner Lichtner, Vita Vita
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