HHV6

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HHV6 HHV7

• Dr Kate Ward
• UCLH

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3.3.24
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SEIZURES

• 13 (21/160) c. 1O HHV-6
• Median age 14 months
• 2 children hospitalised for seizures

NEJM 331 (1994) 432
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HHV-6 -7 ANTIBODIES IN BRITISH CHILDREN
Ward. J Clin Virol (2005) 183-193
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1O HUMAN HERPESVIRUSES-6 -7 (HHV-6/-7)
INFECTIONSMAY BEIMPORTANT CAUSES OF
ENCEPHALITIS IN 1ST 3 YEARS BRITISH
ISLES-WIDE SURVEY STARTED OCT 1998 USING THE
NETWORK OF THE BRITISH PAEDIATRIC SURVEILLANCE
UNIT (BPSU)
3.4.23
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ENCEPHALITIS IN FIRST 3 YEARS THE
STUDYDesign Prospective throout UK
Republic of IrelandPopulation Children aged
2-35 months
3.4.25
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ENCEPHALITIS IN FIRST 3 YEARS THE STUDYCase
ascertainment BPSU via telephoning
reportingReporting definition Suspected
encephalitis /or severe convulsions c fever
Follow up of cases Regardless of
aetiologyLaboratory analysis HHV-6 -7 at
UCL Other infections at local labs
3.4.27
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3.5.17
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HHV-6 -7 IgG AVIDITY TESTS Use
indirect immunofluorescence 1. Ag fixed on
slide. 2. Incubate with test serum. 3.
Wash off serum /- urea (Urea breaks
low avidity Ag-Ab bond) 4. Incubate with
FITC-anti human IgG 5. Compare ab titres
? 8-FOLD REDUCTN LOW AVIDITY
Ward et al., J. Clin. Micro 2001 Ward et al., J.
Virol. Methods 2002
3.5.4.
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EXAMPLE 1O HHV-6 INFECTION
Case 6 - Age 11 months

• _______________________________________Days
  Serum
• HHV-6 IgG HHV-7 IgG DNA
• Titre Avidity Titre Avidity
• _____________________________________________
• 3 lt8 - lt8 - HHV-6
• 7 lt8 - lt8 - HHV-6
• 13 2048 Low NT - -
• 58 512 High lt16 - -

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Age Distribution of 1O HHV-6 /- Prior HHV-7
Infection
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Age Distribution of 1O HHV-7 /- Prior HHV-6
Infection
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QUESTIONHAVE THE 1O INFECTIONS COINCIDED
BY CHANCE WITH NEUROLOGICAL DISEASE?
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Prevalence Past infection/Past infection
Uninfected
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PROOF of CAUSATION

• HHV-6 1O infections
• 13 v 1.66 expected
• Plt0.001

• HHV-7 1O infections
• 14 v 1.34 expected
• Plt0.001

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Comparison of 1O HHV-6 -7 cases

• HHV-6 HHV-7
• No. of cases 13 15
• Days in hospital 9 5
• Max temperature O C 39 38.7
• No. c. convulsions
• None 1 0
• lt15 minutes 2 1
• 15-30 minutes 3 1
• gt30 minutes
• (status epilepticus) 7 13
• No. ventilated/sedated 6 6

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CONCLUSIONS

• 1O HHV-6 -7 infections
• 1. Are equally important causes of febrile
  status epilepticus in the first 2 years of life.
• 2. Burden of disease at c. one year old around
  time of MMR vaccine.
• HHV-6/7 tests needed to exclude misdiagnosis of
  neurological disease as a vaccine reaction.

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THANK YOU TO

• Microbiologists
• Paediatricians
• Virologists
• BPSU
• CDSC
• Wellcome Trust