In adolescents and adults aged 16-39 years, individuals with S. mansoni mono-infection were found to have significantly higher Hb values (mean: 143.7 g/l, 95% CI: 136.3, 151.1 g/l) compared to individuals with neither infection (mean: 131.2 g/l, 95% CI: 127.6, 134.8 g/l) or with P. falciparum mono-infection (mean: 132.1 g/l, 95% CI: 127.9, 136.2 g/l). This evidence concerns the gene GSTM1 and infection.