The virus

Cytomegalovirus is a double-stranded DNA virus and member of the Herpesviridae family of viruses.

Epidemiology

Route of spread

Cytomegalovirus is transmitted via saliva and sexual contact, or from infected donated blood and organs.

Prevalence

Cytomegalovirus infection occurs worldwide and the prevalence of infection varies considerably. In the UK a rule of thumb is that the percentage of the community with CMV infection is equivalent to the age (e.g. approximately 20% of 20-year-olds will have had CMV infection). Prevalence tends to be higher in lower socio-economic groups, people born outside Western Europe, inner city areas and in communities living in overcrowded conditions.

Incubation period

3–6 weeks.

Infectious period

This varies for different groups of people. In immunocompetent people, the virus is present for a few weeks in saliva, blood and some other body fluids after primary infection. In immunocompromised people, the infectious period may be prolonged after primary infection. Also, when they experience reactivation of CMV, the infection may last for weeks or months.

Cytomegalovirus is a herpes virus, which becomes latent in humans once active infection has been resolved. The virus can reactivate to produce another infection later in life – this is much rarer in persons who are not immunocompromised.

At-risk groups

Cytomegalovirus can infect anyone who has saliva or sexual contact with an actively infected person, or who receives blood or organs from a CMV positive person.