Definition

Human herpesvirus (DNA virus) transferred by respiratory droplets and blood transfusions that lies dormant in white blood cells

Epidemiology

CBC showing leukopenia or pancytopenia
Mild elevation in liver enzymes
CMV-IgG positive
Detectable CMV DNA in peripheral blood, though it can rise during intercurrent illness

Solid-organ transplant
- Donor+/Recipient– high risk for reactivation, the the donor organ infecting the recipient
- Donor–/Recipient+ intermediate risk
- Donor+/Recipient+ intermediate risk
- Donor–/Recipient– lowest risk
- High and intermediate risk patients get prophylaxis with valganciclovir for some amount of duration...
Hematologic stem cell transplant
- Donor+/Recipient+ high risk for reactivation
- Donor–/Recipient+ high risk
- Donor+/Recipient– intermediate risk
- Donor–/Recipient– lowest risk
- Preemptive monitoring with weekly CMV DNA PCR starting week 2
Treat if greater than threshold (1425 at McMaster) or if rising titre with symptoms

Even when dormant, can cause mild immunosuppression that predisposes to fungal infections
Asymptomatic shedding in lungs during intercurrent illness
Viremia with influenza-like illness
End-orgam damage
- CMV colitis
- Retinitis in AIDS patient (CD4 < 50-100)
- Organ inflammation of solid-organ transplants
- Pneumonitis in stem cell transplants

Inherent acyclovir resistance
Tyrosine kinase mutation UL97? confers resistance to (val)ganciclovir
Polymerase mutation U54? confers resistance to (val)ganciclovir and foscarnet
Consider resistance if CMV DNA titres not decreasing despite appropriate treatment
Resistance genotyping available