Disease Burden of Primary HHV-6B Infection in Immunocompetent Children

Purpose of Review: Exanthema subitum, which is caused by primary human herpesvirus 6B (HHV-6B) infection, is generally self-limited. However, disease burden due to primary HHV-6B infection has not yet been widely reported. Therefore, we reviewed the burden of emergency room (ER) visits and serious complications by primary HHV-6B infection. Recent Findings: Around 10% of children with fever under 6 years of age seen in ERs had primary HHV-6B infection prior to the coronavirus disease 2019 (COVID-19) pandemic. Non-pharmacological interventions implemented because of the COVID-19 pandemic decreased the frequency of many viral infections, but not ES. Thus, the relative disease burden of primary HHV-6B infection has increased. Central nervous system diseases including febrile seizure and encephalitis are rare complications. Primary HHV-6B infection is the second cause of pediatric acute encephalopathy after influenza in Japan and there is still no effective treatment. Summary: The clinical features and disease burden of primary HHV-6B infection in immunocompetent patients are reviewed.