Molecular epidemiology of cytomegalovirus: viral transmission among children attending a day care center, their parents, and caretakers.

This 26-month prospective study monitored 104 children from one day care center (DCC), and their families, for cytomegalovirus (CMV) infections. Among the children, 14 different strains of CMV were identified by restriction endonuclease analysis of the viral DNA of isolates. Three of these strains infected 44 DCC children and apparently were transmitted within the DCC environment. Only children younger than 3 years of age acquired the DCC-associated CMV strains. Of 75 seronegative children in this age group, 34 acquired DCC-associated CMV strains, and four were infected with unique strains. Among 23 children older than 3 years of age, none acquired the DCC-associated strains, although six were infected with unique strains. Of 18 seronegative mothers, six acquired CMV infections within 3 to 7 months after their children became infected; the strains were identical to those isolated from their children and were DCC associated. Four fathers, three seropositive mothers, and two caretakers also shed DCC-associated strains of CMV. None of the 31 mothers whose children were not infected shed CMV. There was no apparent CMV-associated morbidity. These results prove the frequent transmission of CMV within the DCC environment and from DCC children to their parents. They further suggest that caretakers do acquire CMV from DCC children.