Increasing Frequency of Blackwater Fever in Ugandan Children Hospitalized with Severe Malaria, 2008–2025

Blackwater fever (BWF), which is characterized by dark urine associated with intravascular hemolysis during malaria infection, is increasingly reported among African children hospitalized with severe malaria. To examine temporal trends beyond previously recognized high-frequency districts in eastern Uganda, we analyzed longitudinal data from 3,340 children enrolled in five severe malaria studies conducted from 2008 to 2025 at Mulago National Referral Hospital in central Uganda and Jinja Regional Referral Hospital in southeastern Uganda. Blackwater fever was defined consistently as caregiver-reported passage of dark or cola-colored urine before admission. The frequency of BWF at admission increased from 24 of 150 children (16%) before 2010 to 259 of 489 children (53%) after 2020. In logistic regression models, calendar year remained associated with BWF after adjustment for demographic, clinical, and treatment-related factors (year-over-year odds ratio, 1.18; 95% CI, 1.03-1.34; P = 0.010). These findings support BWF as an emerging severe malaria complication requiring further investigation.