Malaria and Severe Anemia: Thinking beyond Plasmodium falciparum

In this week’s PLOS Medicine, Ric Price and colleagues compare the burden of anemia in different plasmodia species in a robust hospital-based surveillance study in Eastern Indonesia [1]. The risks of severe anemia associated with non-falciparum and mixed species infections are characterized and compared to no malaria infection and monoinfection with Plasmodium falciparum. While the study is observational, and limited in its ability to control for comorbidities (e.g., geohelminth, bacterial infection), the numbers are impressive, with more than 200,000 outpatient and inpatient episodes with hematological assessment. Their findings reveal a significant burden of severe anemia (defined as hemoglobin less than 5 g/dl) due to P. vivax, P. malariae, or mixed species infections (adjusted population attributable fraction 12.2%), in addition to P. falciparum monoinfection (15.1%). Notably, severe anemia in infants attributable to P. vivax was 30.4% compared to 20.5% for P. falciparum. Patients with severe anemia were substantially more likely to be admitted to the hospital (adjusted odds ratio, 6.34 [95% CI 6.00–6.69]) and to die (adjusted odds ratio, 5.80 [95% CI 5.17–6.50]).