Cytomegalovirus (CMV) is a virus that can cause serious health problems for people with weakened immune systems. Measuring CMV levels in the blood can help to identify potential infections and other related illnesses of the central nervous system, lungs, eyes or other organs. Long-lasting CMV infection has been associated with certain autoimmune conditions such as lupus, multiple sclerosis, systemic sclerosis, Type 1 diabetes and Sjogren's syndrome. CMV is implicated in congentical disease among newborns and is one of the infections screened for at birth.