How dangerous is cmv?

Depends: CMV (cytomegalovirus) infection in children and young adults with intact immune system is usually a trivial infection. However, pregnant mother becomes infected the first time, the virus infects her fetus. Sensorineural hearing loss and developmental delay are common sequelae following congenital CMV infection.

Could be: CMV infection is a viral infection of the herpes family .I t can be asymptomatic but it can be fatal if the patient is immunocompromised and it can cause congenital deformities if a pregnant mother got infected.