The peak age of acquisition of primary human herpesvirus 6 infection is between 9 and 21 months, according to results of a population-based study of 277 children followed from birth to 2 years.
Of the 277, 130 (47%) of the children were infected by the age of 24 months (N.Engl. J. Med. 2005;352:768–76).
Human herpesvirus 6 (HHV-6) acquisition was associated with female sex (adjusted hazard ratio of 1.7 and having older siblings (adjusted hazard ratio of 2.1). Of the 227 children, 46% were female, and 52% had at least one sibling, said Danielle M. Zerr, M.D., of the department of pediatrics, the University of Washington, Seattle, and her colleagues.
HHV-6 infection was monitored using polymerase chain reaction on saliva samples obtained weekly by parents using precut filter-paper strips. Serological detection of anti-HHV-6 antibodies was performed whenever a blood sample was taken from the child for other purposes.
Of the 81 children with a well-defined time of HHV-6 acquisition, 93% showed symptoms, most commonly fussiness (69%), rhinorrhea (65%), and fever (57%), with less-frequent occurrences of cough (33%), rash (31%), and diarrhea (26%).
Roseola, a clinical syndrome considered relatively specific for HHV-6, occurred in only 23% of the 81 children. No seizures were reported. This was “in contrast to emergency department-based studies, in which seizures occurred in as many as 13% of children with primary HHV-6 infection,” they wrote.
Previous serologic studies have shown that HHV-6 infects 90% of children by 2 years of age, and it has been estimated that 20% of emergency department visits for fever are due to primary HHV-6 infection.