HV6/7

Question 1

Describe HHV
- DNA/RNA
- Species
- Which species is responsible for human pathogenesis
- Which %of people have CI HV6 and which species

Answer 1

• dsDNA, enveloped virus approx 200nm in diameter
• HHV6A/B with B being responsible for human disease
• 1% have CIHV6 with 1/3 having A and 2/3 having B amongst transplant recipients

Question 2

HHV6B in the immunocompetent?

Answer 2

Roseola infantum
- High fever for 3-7 days
- rash on trunk neck in face
- common cause of febrile convulsions (10% of all cases of febrile convulsions)

V rarely encephalitis

Question 3

HHV6B detected in the blood of a HSCT patient 3 months post transplant. They are being tested as they have become forgetful.

• What are the next steps?
• What is the possible diagnosis?

Answer 3

• Exclude ciHHV6 by testing pre transplant sample from recipient and, if possible, pre transplant sample from donor.
• If still trying to exclude CiHHV6 then digital droplet PCR or human genome:viral genome PCR may help clarify.
  – NB CIHHV6 tends to have a higher viral load above log5.5 copies/ml
• CSF testing of HHV6 should be done

The possible diagnosis is limbic encephalitis. Tends to be more subacute than other viral enephalitides. presents with seizures, short term memory deficit and personality change.

NB FISH can also be used to detect chromosomal HHV6 integration or testing of hair follicles will also demonstrate this.

Question 4

Management of HHV6B encephalitis in SCT
- Drugs
- duration
- stopping rules

Answer 4

Foscarnet of ganciclovir (cidofovir possible but little evidence basis)

• continued for at least three week and until testing demonstrates clearance of HHV6B from blood and ideally csf.