Cytomegalovirus infection (CMV)

Cytomegalovirus (CMV) is a widespread herpesvirus that most people acquire at some point in life. In a healthy child or adult, the first infection usually causes no symptoms at all, or a mild glandular-fever-like illness with tiredness, fever and swollen glands; the immune system then controls it and the virus stays dormant in the body for life, sometimes reactivating harmlessly. Its clinical significance is concentrated in two groups. First, in pregnancy: a first (primary) CMV infection can cross to the baby (congenital CMV), and is a leading infectious cause of hearing loss and developmental problems in newborns — which is why CMV immune status can matter and why hygiene precautions are advised for susceptible pregnant women. Second, in people with weakened immunity — such as transplant recipients or those with advanced HIV — CMV can cause serious disease, infecting the eyes (retinitis), gut, lungs or other organs, either as a new infection or by reactivating. Diagnosis uses antibody tests (IgG for past exposure, IgM for recent infection) and, where active disease is suspected, direct viral detection (PCR). So CMV is common and usually trivial, but genuinely important in these specific settings.

• CMV IgG and IgM — IgG shows past exposure/immunity; IgM suggests a recent or current infection.
• CMV avidity testing — helps date an infection, especially in pregnancy.
• CMV PCR (viral load) — detects and quantifies active infection, used in immune-weakened patients.
• Lymphocytes and blood count — a mono-like picture, sometimes with atypical lymphocytes.
• Liver markers (ALT/AST) — can be mildly raised in the mono-like illness.

• Often none in healthy people
• A mono-like illness: fatigue, fever, sore throat, swollen glands
• Muscle aches and malaise
• In pregnancy: usually silent in the mother but a risk to the baby
• In weakened immunity: serious organ disease (e.g. visual changes from retinitis, gut or lung symptoms)