In 2000, Moulds et al. found that both the Sl2 and McCb allele frequencies were very rare in European-Americans (n = 112, both Sl2 and McCb; 1%) compared to African-Americans (n = 150, 44% (Sl2) and 39% (McCb)), whereas the frequencies in a Malian population (n = 139) were 70% (Sl2) and 49% (McCb), and suggested that Sl2 might offer a protective advantage against severe malaria [16]. Here, MCCC1 is linked to malaria.