The epidemiology of severe malaria at Manhiça District Hospital, Mozambique: a retrospective analysis of 20 years of malaria admissions surveillance data

Background: Most malaria burden estimates rely on modelling infection prevalence to case incidence data, with insufficient attention having been paid to the changing clinical presentation of severe disease and its relationship with changing transmission intensity. We present 20 years of longitudinal surveillance data to contribute to the understanding of the relationship between malaria transmission and the burden and clinical presentation of severe malaria and to inform policy.

Methods: This retrospective analysis of clinical surveillance hospital data included all children younger than 15 years admitted with malaria to Manhiça District Hospital (MDH), Mozambique, from July 1, 1997, to June 30, 2017. Case fatality ratios (CFRs) were calculated as the number of patients who died having a specific diagnosis or syndrome divided by the total number of patients with known outcome admitted with that diagnosis or syndrome.

Findings: Over the study period, 32 138 children were admitted to MDH with a malaria diagnosis. Malaria accounted for a large proportion of admissions, ranging from 4083 (76·9%) of 5307 admissions in 2000-01 to 706 (27·5%) of 2568 admissions in 2010-11. Since 2000-02, the absolute and relative number of malaria admissions and deaths presented a decreasing trend. The age pattern of patients with malaria shifted to older ages with a median age of 1·7 years (IQR 0·9-3·0) in 1997-2006 and 2·6 years (IQR 1·3-4·4) in 2006-17, although most malaria deaths (60-88% in 2009-17) still occurred in children younger than 5 years. The clinical presentation of severe malaria changed, with an increase in cerebral malaria and a decrease in severe anaemia and respiratory distress, leading to similar yearly cases for the three syndromes. CFRs for severe malaria fluctuated between 1·1% (2 of 186 in 2014-15) and 7·2% (11 of 152 in 2010-11), varying by severe malaria syndrome (3·3% [70 of 2105] for severe anaemia, 5·1% [191 of 3777] for respiratory distress, and 14·8% [72 of 487] for cerebral malaria). Overall malaria CFRs (1·8% [543 of 30 163]) did not vary by age group.

Interpretation: Despite the unprecedented scale up of malaria control tools, malaria still represented around 30-40% of paediatric hospital admissions in 2006-17. The age shift towards older children was not accompanied by an increase in severe malaria or deaths; however, control programmes should consider adapting their high-risk target groups to include older children. Malaria remains a leading cause of disease and health-care system use and the massive unfinished malaria control agenda warrants intensified efforts.

Funding: Spanish Agency for International Cooperation and Development.