Genetic variation at the FUT2 locus on chromosome 19 (secretor/non secretor) predisposes to at least two infectious diseases. Being a secretor leads to genetic immunity to gastroenteritis in adults caused by infection by the Norwalk norovirus and fucosylated oligosaccharides in the breastmilk of secretors are protective against gastroenteritis children. Using genotype data I will examine whether protective effects of maternal secrector status are present for breastfed children.