HHV 6 & 7

HHV 6 and HHV 7

HHV 6 is associated with exanthem subitum (roseola).

There are two serotypes -HHV 6 type A and HHV 6 type B

HHV 7 has only one serotype.

Transmission

Direct person to person through contact with saliva.

Incubation period- 3 to 4 weeks

Clinical presentation

HHV 6

In infants

Infants infected with HHV 6 presents mainly with fever.

There are some evidences that suggest most febril convulsion is associated with HHV 6 infection.

In Children

Fever
Skin rash appears after the temperature settle down to the normal range. The rash is characteristically maculopapular.
Most children acquire infection before the age of 5 yrs.

In adults

Most are asymptomatic.

Some patient presents with mononucleosis like illness.

Others present with

Encephalomyelitis
Rarely patient presents with hepatitis

In immunocompromised patients

Reactivation in Immunocompetent patients are normally asymptomatic and on the other hand most active infections are caused by primary infection.

The main presentations includes

Ø Pneumonitis

Ø Bone marrow suppression

Ø Encephalitis

Ø Hepatitis

Ø Skin rash

Reactivation occur after 3-4 weeks of transplant.

HHV 7

In children

Fever and skin rash are common.

There are only a few study on the HHV 7, however there is a consences that HHV7 may not be as important as CMV in transplant patients.

Investigations

Depending on the presentation.

Diagnostic tests

1.HHV6

Primary infection

Serum for HHV 6 IgM. Commercial tests are available but is not used widely.

Encephalitis

CSF, and blood in EDTA for HHV 6 PCR

Immunocompromised patients

EDTA blood, BAL or biopsy for HHV 6 DNA PCR.

Screening

Screening is not routinely done, however where the test is available testing for HHV 6 before transplant is important particularly in children.

2. HHV 7

Testing is not routinely done.

Treatment

Treatment not usually required.

Immunocompromised patient may be treated with Gancyclovir , Cidofovir or Foscarnet.

Those patients on Gancyclovir prophylaxis do not have HHV 6 reactivation.

From experience, Cidofovir seems to be more effective than the other antivirals.

Prevention

There is no vaccine.

Screening is not routinely done.

Some centre carry out a weekly surveillance to detect HHV 6 PCR.