Background: Adolescents are increasingly recognised as an epidemiologically relevant but under-targeted group for malaria in sub-Saharan Africa. However, clinical and operational data from Central Africa, including Gabon, remain limited.

Methods: We analysed routine data from the malaria sentinel surveillance site of the Estuaire Regional Hospital in Melen, Gabon. Febrile patients or those with a recent history of fever received free malaria testing. Adolescents aged 10–19 years with microscopy-confirmed malaria (quality-controlled thick blood smear using the Lambaréné method) were included. Parasitaemia was summarised using medians and interquartile ranges (IQR). Group comparisons used the Mann–Whitney U test; categorical comparisons used χ² or Fisher’s exact test as appropriate.

Results: A total of 1,262 adolescents were included; median age was 13 years (IQR: 12–14) and 52.6% were male (sex ratio M/F 1.11). Median temperature at presentation was 38.0°C (IQR: 37.0–39.0). Overall median parasitaemia was 4,200 parasites/µL (IQR: 700–21,000). High parasitaemia (>100,000–250,000/µL) occurred in 4.0% and hyperparasitaemia (>250,000/µL) in 1.0% of cases. Parasitaemia did not differ by age group (p = 0.118) or sex (p = 0.867). Among participants with available data (n=96), prior self-medication was reported in 18.8% and was associated with markedly lower parasitaemia (242 [35–2,100] vs 10,500 [2,275–39,025] parasites/µL; p < 0.001).

Conclusions: Adolescents in this Gabonese sentinel site showed heterogeneous parasite burdens, including highdensity infections, and self-medication strongly modified parasitaemia at presentation—supporting adolescent-inclusive surveillance and behavioural measurement in routine monitoring.