Background
Blackwater fever (BWF) is malaria complication in which red blood cells burst, releasing hemoglobin into blood vessels and urine; recurrent episodes requiring repeated blood transfusions are common. In May 2021, districts in Eastern Uganda reported an increase in suspected BWF affecting children. In June 2021, we investigated to confirm the outbreak, assess the scope, and identify associated risk factors.
Methods
We defined a case as onset of dark or red urine with ≥1 of: fever >37oC, anorexia, fatigue, abdominal pain, abdominal distention, anemia, jaundice, headaches, or vomiting in a pediatric patient attending Mbale, Soroti, or Jinja Regional Referral Hospitals (RRHs). We abstracted medical records data for cases identified from January 2019-May 2021 and conducted a case-control study to identify possible risk factors. Controls were pediatric patients who had never passed dark-colored urine. We interviewed caretakers on clinical presentation, history, and exposures. We calculated attack rates and conducted multivariate logistic regression to identify associated
factors.
Results
Among 4,913 case-persons identified during January 2019-May 2021, 2,969 (60%) were males; 26 died (CFR=0.5%). Attack rates were similar in 2019 (2.3/10,000) and 2020 (2.5/10,000). Over the study period, the fewest cases were recorded during March, April, and May each year. On average, case-persons spent 4 days in hospital and required 3 blood transfusions per episode. Among 88 cases and 88 controls, delaying >48 hours between malaria symptom onset and receiving care increased odds of BWF (OR=23, CI: 1.01–535). Having sickle cell anaemia, hepatitis B, or HIV were not associated with BWF.
Conclusion
BWF caused substantial morbidity among children in Eastern Uganda during our study period. Delays to care were associated with BWF. Future studies should expand case capture sites to identify geographic boundariesvof this problem in Uganda. Immediate care-seeking should be emphasized for children with a history of BWF.