TO THE EDITOR—We thank Yates et al [1] for their interest in our article and positive comments regarding careful control of potential confounding variables in the analyses [2]. In addition to confounding, other types of bias—including collider bias (the subject addressed by Yates et al) as well as recall bias, regression dilution, and reverse causation bias (which are not mentioned)—are important to consider when interpreting the results of the association between human cytomegalovirus (HCMV) and cardiovascular disease (CVD).