"The ancient and the new": is there an interaction between cytomegalovirus and SARS-CoV-2 infection?

The SARS-CoV-2 pandemic represents one of the greatest infectious challenges to humanity in recent history. One of the striking features of infection is the heterogeneous clinical response with worse outcomes observed in older patients and those with underlying health conditions. To date the potential impact of previous infection history has been poorly investigated as a potential determinant of risk. Cytomegalovirus (CMV), a persistent herpesvirus infection whose prevalence increases with age, is a major modulator of immune function and several observations suggest that infection might act to influence clinical outcome following SARS-CoV-2 infection. In particular, CMV is associated with the acceleration of immune senescence and has been linked to a range of cardiovascular and metabolic disorders. This review addresses mechanisms by which cytomegalovirus infection may act to worsen the clinical outcome of SARS-CoV-2 infection, discusses how these potential links could be investigated, and assesses the potential significance of any findings that emerge.