HCMV is a β-herpesvirus that infects 70–90% of the general population, causing acute, persistent, or lifelong latent infection . HCMV infections are typically subclinical and serious disease occurs mainly in immune-compromised individuals . Overall, HCMV serostatus has not been positively correlated with breast cancer; however, women with breast cancer were found to have higher mean HCMV IgG levels in an Australian case–control study , suggesting that they might have experienced a recent infection. Analysis of a Norwegian cohort by the same group also revealed that elevation of HCMV IgG, but not EBV IgG levels, preceded the development of breast cancer in some women .