In summary, accumulating data suggest that CMV infection is a frequent occurrence in critically ill patients. Considering a large number of patients requiring ICU level of care, the scope of impact of CMV infection in these patients may be equally or potentially wider than in other immunocompromised hosts traditionally recognized to be at risk for CMV infection. For example in the USA, an estimated 383,000 cases with sepsis require ICU admission as opposed to 28,360 solid organ transplant cases yearly [72, 73] . Mortality rate in patients with sepsis ranges from 20 to 50% and approaches 70% in those with multiple organ failure [74] . Furthermore, the incidence of sepsis and the number of sepsis-related deaths appear to be increasing [73, 74] . Precise identification of the role of CMV as a contributor to outcomes in these patients may therefore have far reaching implications. Subsets of critically ill patients who are at risk for developing CMV infection and for poor outcomes remains to be determined. These studies have significant implications for future investigations to determine the potential benefits and for guiding the study design to evaluate the impact of antiviral agents on clinically meaningful outcomes in critically ill patients.