The study, a mixed retrospective-prospective observational investigation published in BMC Infectious Diseases, enrolled laboratory-confirmed malaria cases among adults presenting to the emergency departments of the two hospitals between October 1 and December 31, 2025. The researchers applied the 2014 World Health Organization criteria for severe malaria, a standardized set of clinical and laboratory thresholds that includes coma, severe anaemia, renal impairment, respiratory distress, and other life-threatening features. By combining retrospective chart review with prospective observation, the team captured a realistic cross-section of how malaria actually presents in emergency settings in Central Ethiopia, rather than relying solely on curated inpatient populations.

The species distribution among the 318 laboratory-confirmed cases was striking. Plasmodium vivax accounted for 49.7 percent of infections, making it the single most prevalent species. Plasmodium falciparum followed at 38.4 percent, while mixed infections of both parasites made up the remaining 11.9 percent. This near-majority share for P. vivax marks a significant shift from the historical pattern in Ethiopia and much of Africa, where falciparum has traditionally dominated case counts and where vivax malaria was once considered a minor contributor to the regional burden.

Even more consequential is what the researchers found when they assessed disease severity. Severe malaria, as defined by WHO criteria, was diagnosed in 65.7 percent of all confirmed cases—an extraordinarily high proportion for an emergency department cohort. Severe anaemia, defined as a haemoglobin concentration below 5 grams per decilitre, was the most common severity criterion, present in 33.3 percent of patients. Anaemia at this level represents a medical emergency in its own right, depriving tissues of oxygen and placing particular strain on the heart, and it frequently necessitates blood transfusion alongside antiparasitic therapy.

When the analysis turned to the question of whether species mattered for severity, the answer was sobering. Severe malaria occurred in 65.2 percent of patients infected with P. vivax and 67.2 percent of those infected with P. falciparum—figures that are statistically indistinguishable. Using bivariate logistic regression, the investigators found no statistically significant association between malaria species and the likelihood of severe disease. In practical terms, the parasite that causes the majority of severe cases in a region cannot simply be assumed to be falciparum, and clinicians who triage vivax infections as inherently benign may dangerously underestimate the risk facing their patients.

The clinical outcomes documented in the study underscore the stakes. Most patients, 62.3 percent, were discharged directly from the emergency department after treatment, while 27.7 percent required admission to medical wards for ongoing care. In-hospital mortality stood at 4.4 percent—a figure that, while lower than mortality rates historically reported for severe falciparum malaria in intensive care settings, represents a substantial toll of deaths attributable to a disease in which both species contributed nearly equally to severe presentations. The high discharge rate also raises questions about the adequacy of follow-up, particularly for patients with vivax infections who require additional therapy beyond the acute episode.

That additional therapy is a cornerstone of the study’s conclusions. Unlike P. falciparum, which exists in the human body only as blood-stage parasites, P. vivax harbors a latent liver stage known as the hypnozoite. These dormant forms can reactivate weeks or months after the initial infection, causing relapses without any new mosquito bite. Eliminating the hypnozoites requires so-called radical cure, typically with the drug primaquine, which demands careful screening for glucose-6-phosphate dehydrogenase deficiency because the medication can trigger severe haemolysis in susceptible individuals. The authors emphasize that appropriate radical cure for P. vivax remains essential for malaria control and elimination efforts, precisely because untreated relapses sustain transmission and add cumulative burden of anaemia and illness.

The findings arrive at a pivotal moment for Ethiopia’s malaria programme. The country has pursued ambitious elimination targets, and declining overall transmission can paradoxically reshape the epidemiology of the disease, reducing acquired immunity in the population and allowing species that were previously overshadowed to emerge in greater numbers. A species shift toward vivax carries specific programmatic implications: diagnostic platforms must reliably distinguish the two species, since treatment algorithms differ; health systems must secure access to radical cure with appropriate G6PD screening; and surveillance frameworks designed around falciparum metrics may need recalibration to capture the true vivax burden.

The authors of the study argue that strengthening early diagnosis, prompt treatment, and species-specific case management is essential if Ethiopia is to maintain momentum toward malaria control and elimination. The near-parity in severe disease between the two species suggests that the clinical distinction between ‘benign’ and ‘malignant’ malaria, entrenched in textbooks and training curricula, may be misleading in settings like Central Ethiopia. Emergency clinicians managing febrile adults in the region should treat any confirmed malaria infection as potentially severe, regardless of the identified species, and should maintain a low threshold for transfusion in patients with profound anaemia.

The research also carries implications for the global malaria agenda. As endemic countries approach elimination, P. vivax is increasingly recognized as the parasite most likely to stand between them and their goal, owing to its relapsing biology and its ability to sustain transmission at low parasite densities that evade routine diagnostics. Evidence from Central Ethiopia that vivax now predominates in emergency presentations—and contributes to severe disease at rates equivalent to falciparum—adds clinical urgency to that strategic concern. Investment in tools such as highly sensitive rapid diagnostic tests, G6PD point-of-care testing, and tafenoquine, a single-dose radical cure agent, would directly address the gaps this study exposes. For the patients arriving at emergency departments in Hosanna and Werabe, the message is simpler: the malaria parasite in their blood, whatever its species, can make them critically ill, and the health system must be prepared to recognize and respond to that reality.

Subject of Research: The emerging predominance of Plasmodium vivax and its contribution to severe malaria among adults in Central Ethiopia.

Article Title: Emerging predominance of Plasmodium vivax and its contribution to severe malaria in Central Ethiopia: a mixed retrospective-prospective study from two tertiary hospitals

Article References: Emerging predominance of Plasmodium vivax and its contribution to severe malaria in Central Ethiopia: a mixed retrospective-prospective study from two tertiary hospitals. (n.d.). https://doi.org/10.1186/s12879-026-14383-3

Image Credits: AI Generated

DOI: 10.1186/s12879-026-14383-3

Keywords: malaria, Plasmodium vivax, Plasmodium falciparum, severe malaria, severe anaemia, species shift, Ethiopia, emergency department, radical cure, malaria elimination, tropical medicine, BMC Infectious Diseases

The retrospective study covered January 2023 through October 2025 and began with a hospital-wide sweep of emergency department and inpatient records carrying any ICD-10 malaria code. Of 519 laboratory-confirmed malaria diagnoses recorded during the period, 428 (82.5 percent) were P. vivax, 88 (17.0 percent) were P. falciparum, two were mixed infections, and one was P. malariae. From this pool, 127 patients met the analytic criteria: microscopy-confirmed malaria, at least one dose of intravenous artesunate given for severe disease or inability to tolerate oral therapy, survival of at least 24 hours after admission, and laboratory results available at two or more time points. Notably, 22.7 percent of vivax patients and 30.7 percent of falciparum patients entered the cohort, a proportion of hospitalization far higher than the 1.6 to 3.2 percent reported in earlier Peruvian and Brazilian Amazonian series.

The headline result is stark in its symmetry. Severe malaria, defined by at least one criterion from the 2022 WHO guidelines, occurred in 51 of 97 vivax patients (52.6 percent) and 14 of 27 falciparum patients (51.9 percent). That equivalence emerged despite a marked asymmetry in underlying vulnerability: recognized risk factors or comorbidities were recorded in 59.3 percent of falciparum patients but only 26.8 percent of vivax patients, a difference largely driven by pregnancy. In other words, vivax patients reached comparable severity with a lighter load of predisposing conditions, suggesting that the parasite itself, rather than patient frailty, was driving the clinical picture.

The spectrum of severity criteria also overlapped substantially between species. Prostration and altered consciousness were the most frequent clinical manifestations, while severe anaemia led the biochemical criteria. Sixty-six of the 67 patients who ultimately fulfilled a severity criterion already met one at admission, but nine patients developed new or recurrent WHO-recognized manifestations during hospitalization, including impaired consciousness, shock, metabolic acidosis, jaundice, severe anaemia, haemoglobinuria and renal impairment at various time points after admission. The authors argue that this longitudinal evolution supports continued clinical and laboratory reassessment throughout the hospital stay, even though formal repeated screening against all criteria is not mandated by current WHO guidance.

Laboratory data reinforced the impression that vivax malaria is haematologically aggressive. At baseline, patients with severe disease had significantly lower haemoglobin and haematocrit values than non-severe patients, and haemoglobin remained lower in severe cases after treatment. In non-severe malaria, falciparum infection was actually associated with a less favourable baseline profile, with lower haemoglobin and haematocrit than vivax. Strikingly, platelet counts were significantly higher in falciparum infections in both severity strata, echoing prior reports that thrombocytopenia in vivax malaria can be as marked as, or more marked than, that seen in falciparum disease, and often out of proportion to the peripheral parasite density visible on a blood smear.

That dissociation between circulating parasites and clinical damage has a plausible biological explanation. Human splenectomy studies have shown that P. vivax–infected erythrocytes accumulate alongside immature reticulocytes in the red pulp of the spleen, creating a hidden reservoir that peripheral microscopy systematically undercounts. A larger total parasite biomass has been linked to thrombocytopenia, inflammatory activation, endothelial dysfunction and disruption of the vascular glycocalyx. Endothelial activation in acute vivax malaria is pronounced and associated with impaired microvascular reactivity and reduced tissue perfusion, and unlike in severe falciparum malaria it does not appear to be driven by intravascular haemolysis, pointing instead to depleted arginine and nitric oxide bioavailability as a key pathway toward organ dysfunction.

The relapsing biology of P. vivax adds a cumulative dimension to its threat. Reactivation of dormant hepatic hypnozoites or release of parasites from extravascular reservoirs can produce recurrent episodes before haematological recovery is complete, progressively eroding haemoglobin reserves and nutritional status and priming patients for severe disease in later attacks. This mechanism may be especially relevant in the Peruvian Amazon, where vivax predominates and more than half of the study patients, 52.8 percent, reported previous malaria episodes. Evidence from Indonesia suggests that although early mortality after a first episode is higher with falciparum, the mortality gap narrows and may even reverse after repeated vivax infections.

Treatment outcomes in the cohort were generally favourable. The median time to parasite clearance after intravenous artesunate was 48 hours, with no substantial difference by severity, and 93.3 percent of the 89 patients evaluated at 72 hours had completely cleared parasites on smear. The median hospital stay was five days, and all surviving patients were switched to oral antimalarial therapy after parenteral treatment. Yet the study also exposed gaps in pre-hospital care: 60.6 percent of patients had received no antimalarial treatment before admission, and 14.2 percent had been given empirical therapy with no antimalarial activity, a pattern at odds with WHO recommendations for prompt effective treatment after diagnosis.

The single death in the cohort underscores how conventional severity criteria can fail pregnant patients. A pregnant woman with falciparum malaria, admitted eight days after symptom onset, met neither clinical nor biochemical severity criteria at admission and had a normal platelet count. Roughly 48 hours after starting artesunate, her platelets had collapsed from 253 to 36 thousand per microlitre, she remained parasitaemic, and moderate anaemia persisted. She suffered foetal loss on hospital day five, followed by massive obstetric haemorrhage, and died the next day despite timely obstetric intervention and transfusion. The authors note that while the recorded cause of death was uterine haemorrhage, falciparum infection in pregnancy is an established cause of stillbirth, and the case illustrates how difficult it can be to disentangle immediate from contributing causes of maternal death.

Coinfections added further complexity to the clinical landscape. Dengue was identified in 14 patients, eight with severe and six with non-severe malaria, alongside two cases of bacterial sepsis and one of leptospirosis, while intestinal parasitosis was detected in 21 patients. Previous work has suggested that dengue–malaria coinfection may worsen haematological complications, though the small number of coinfected cases here precluded any conclusion. The authors also acknowledge the limits of their retrospective, single-centre design: incomplete follow-up laboratories, cultures obtained only when infection was clinically suspected, reliance on microscopy with limited sensitivity for low-level or mixed infections, and the likelihood that the most severely ill patients died before ever reaching the hospital. Even so, the central message stands. In this low-transmission Amazonian setting, P. vivax carried a burden of WHO-defined severe malaria comparable to P. falciparum, with broadly similar clinical, laboratory and parasitological profiles, and the authors conclude that both locally prevalent species warrant the same degree of clinical vigilance.

Subject of Research: Comparative severity of Plasmodium vivax and Plasmodium falciparum malaria in hospitalized patients in the Peruvian Amazon

Article Title: Comparable severity of Plasmodium vivax and Plasmodium falciparum malaria in hospitalized patients in the Peruvian Amazon

Article References: Bresciani, L., Guardiani, M., Rojas-Blasquez, M., Ramirez, E., Iaquinandi, S., Martel, C., Velarde-Mera, M., Sifuentes-Vidigal, S., Carraro, A., Russo, G., Pasquazzi, C., Celis, J. C., Casapia Morales, M., Nicastri, E., Asayag, C. R., Lichtner, M., & Vita, S. (2026). Comparable severity of Plasmodium vivax and Plasmodium falciparum malaria in hospitalized patients in the Peruvian Amazon. New Microbes and New Infections, 73, Article 101849. https://doi.org/10.1016/j.nmni.2026.101849

Image Credits: AI Generated

DOI: 10.1016/j.nmni.2026.101849

Keywords: malaria, Plasmodium vivax, Plasmodium falciparum, severe malaria, Peruvian Amazon, WHO severity criteria, intravenous artesunate, thrombocytopenia, severe anaemia, malaria in pregnancy, parasite clearance, endothelial dysfunction