The Seroprevalence of HHV-7 in Children in Russia

Background: There are no data on HHV-7 seroprevalence in Russia. Previously we detected HHV-7 DNA in plasma of 8-10% children with exanthem subitum and fever without rash.

Objective: We aimed to comparative study of the seroprevalence of HHV-7 and HHV-6 in children in Russia.

Methods: The pilot study included 105 children, aged from 10 days to 10 years, and diagnosed with respiratory tract infections. All children were recruited at St.Petersburg Filatov`s Children Hospital between March–April 2016. Serum samples were tested for IgG to HHV-7 and HHV-6 by indirect immunofluorescent assays and ELISA correspondingly. We distributed patients into five groups, according to their ages: under six months, from six months to 1 year, from one year to 2 years, 2-4 years, and older than 4 years.

Results: Antibody prevalence for HHV-7 was three times lower than HHV-6. There were only 16% patients seropositive to HHV-7, compared to 52% seropositive to HHV-6. Under 6 months old the frequency of HHV-7 seropositive was 14,8%, which possible was due to maternal antibodies. From 6 months to 4 years the HHV-7 seroprevalence was about 8-13%. In children older than 4 years the rate of seropositivity rised to 28%.

Conclusion: We can conclude that contact to HHV-7 occurs later in life than to HHV-6, predominantly after age of four years. The seroprevalence to HHV-7 is lower than to HHV-6 in children under 10 years. The sample size of our study is too small to extrapolate on Russian population and other seroprevalence studies are needed.