The few studies addressing this question in birds have yielded disparate results, the analysis of field infection with H5N1 HPAI suggesting a hierarchy of survival based on the B haplotype, with B21 giving complete protection from mortality18, whilst experimental infection of congenic lines suggested that B21 conferred only partial protection of between 60% and 30% and that non-MHC genes might also be important19. Here, HLA-C is linked to infection.