IgA antibodies to B. pertussis antigens in whole-cell sonicate is known to lack specificity[45] compared to IgA antibodies to pertussis toxin.[30] Indeed, single high values of IgA and IgG antibodies to pertussis toxin indicate infections in adults, and IgA is more indicative of a recent antibody response, although less consistent than IgG.[30] However, we excluded causes of the epidemic other than pertussis and used culture, PCR, and IgG against pertussis toxin to positively identify pertussis cases. This evidence concerns the gene CD79A and pertussis.