In addition, a strong linkage disequilibrium was observed between the CCR5 locus and two microsatellite loci in Caucasian populations, suggesting an estimated age for the allele of 700 years (between 275 and 1875), which may indicate its positive selection during epidemics in Europe (such as Plague or smallpox pandemics that have taken place over the past 1000 years), consequently reducing the susceptibility of modern Europeans to HIV-1 infection compared to Africans [303]. Here, CCR5 is linked to HIV-1 infection.