KRT1 and infection: Though the K1 and Mad20 allelic families appear to be equally distributed, when these infections were analysed over time there was a decrease in the detection of K1 allele-types (74.7% to 44.7% between 2003-2007), complemented by an increase in the detection Mad20 allele-types (20.2% to 55.3% between 2003-2007).