Clinical and epidemiological features of infections caused by HHV-6A and HHV-6B

Abstract

Objective. To determine the detection rates of HHV-6A and HHV-6B compared to other herpes viruses in children of different age groups. Materials and Methods. A total of 128 patients with symptoms of respiratory viral infections (RVI) aged from 1 to 16 years and 101 otherwise healthy children. A comprehensive examination of the patients, including ELISA, indirect immunofluorescence assay, rapid culture method, PCR, and determination of nucleotide sequences of HHV-6 was performed. Children positive for HHV-6 markers (antibodies, early and late antigens) and positive for HHV-6 DNA were selected into one group (n=59), of which 14 children aged from 3 to 10 years were healthy and 45 children (<3 years of age [20 children] and ≥3 years of age [25 children]) had clinical manifestations of RVI. Results. The incidence rates of acute HHV-6 infection and HHV-6 reactivation were similar between healthy children and children with RVI symptoms (21.9% each). The active Epstein-Barr Virus (EBV) infection took a second place among examined children: acute EBV infection and EBV reactivation were determined in 19 (14.8%) and 10 (7.8%) children, respectively. The incidence rates of HHV-6A and HHV6B among children with RVI symptoms were similar (55.5% and 42.2%, respectively) whereas HHV-6B was predominant in healthy children (85.7%). The HHV-6A was more common (70%) in children under 3 years of age, but HHV-6B was more frequent (67%) in children aged 3 years and older. The most often initial manifestations of HHV-6A infection were acute fever and catarrhal syndrome; whereas HHV-6B was found more frequently in otherwise healthy children. A sudden exanthema and febrile seizures were significantly more common symptoms in children with HHV-6A infection, whereas tonsillar enlargement with exudate and swollen lymph nodes were observed more frequently in children with HHV-6B infection. Conclusions. HHV-6A more often causes acute infection in children less than 3 years of age, which is characterized by fever, febrile seizures, rash (roseola), and upper respiratory tract infection with significant catarrhal syndrome. HHV-6B more often causes acute infection in children aged 3 years and older and is rarely presented with specific symptoms of HHV-6 infection, such as sudden exanthema and febrile seizures. HHV-6B is characterized by lymphoid tissue proliferation (tonsillar enlargement and lymphadenopathy) and hepatomegaly in all age groups of children.