title: Human herpesviruses-6 and -7 each cause significant neurological morbidity in Britain and Ireland.
abstract: BACKGROUND
  Primary human herpesvirus-6 and -7 (HHV-6/-7) infections cause febrile illness sometimes complicated by convulsions and rarely encephalopathy.
  
  
  OBJECTIVE
  To explore the extent of such HHV-6 and -7 induced disease in young children.
  
  
  METHODS
  In a three year prospective study in Britain and Ireland, 205 children (2-35 months old) hospitalised with suspected encephalitis and/or severe illness with fever and convulsions were reported via the British Paediatric Surveillance Unit network. Blood samples were tested for primary HHV-6 and -7 infections.
  
  
  RESULTS
  26/156 (17%) of children aged 2-23 months had primary infection (11 HHV-6; 13 HHV-7; two with both viruses) coinciding with the acute illness; this was much higher than the about three cases expected by chance. All 26 were pyrexial; 25 had convulsions (18 status epilepticus), 11 requiring ventilation. Median hospital stay was 7.5 days. For HHV-6 primary infection the median age was 53 weeks (range 42-94) and the distribution differed from that of uninfected children; for HHV-7, the median was 60 weeks (range 17-102) and the distribution did not differ for the uninfected. Fewer (5/15) children with primary HHV-7 infection had previously been infected with HHV-6 than expected.
  
  
  CONCLUSIONS
  Primary HHV-6 and HHV-7 infections accounted for a significant proportion of cases in those <2 years old of severe illness with fever and convulsions requiring hospital admission; each virus contributed equally. Predisposing factors are age for HHV-6 and no previous infection with HHV-6 for HHV-7. Children with such neurological disease should be investigated for primary HHV-6/-7 infections, especially in rare cases coinciding by chance with immunisation to exclude misdiagnosis as vaccine reactions.
authors.affiliation: Department of Virology, Royal Free and University College Medical School, Windeyer Institute of Medical Sciences, London, UK. k.n.ward@ucl.ac.uk
authors.forename: K N
authors.initials: KN
authors.lastname: Ward
authors.forename: N J
authors.initials: NJ
authors.lastname: Andrews
authors.forename: C M
authors.initials: CM
authors.lastname: Verity
authors.forename: E
authors.initials: E
authors.lastname: Miller
authors.forename: E M
authors.initials: EM
authors.lastname: Ross
mesh_terms: D002675:Child, Preschool; D018792:Encephalitis, Viral / Q000453:epidemiology* / Q000821:virology; D005077:Exanthema Subitum / Q000453:epidemiology; D005334:Fever / Q000453:epidemiology / Q000821:virology; D006306:Health Surveys; D015654:Herpesvirus 6, Human; D016199:Herpesvirus 7, Human; D006801:Humans; D007223:Infant; D007494:Ireland / Q000453:epidemiology; D015995:Prevalence; D011446:Prospective Studies; D019349:Roseolovirus Infections / Q000453:epidemiology*; D012640:Seizures / Q000453:epidemiology / Q000821:virology; D006113:United Kingdom / Q000453:epidemiology