A very common virus which causes a mild ‘flu-like’ illness. Individuals in good health make a full recovery and are usually unaware of the infection. We may test for antibodies against the virus. A positive test indicates that the individual has had CMV infection and may still have the virus. Having antibodies to CMV is of no significance to the health of the donor. However, for some patients with a poor immune system (particularly small babies), CMV can cause a life-threatening illness. CMV-positive blood is safe for most patients, and donors are not informed of a positive result.