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Human Herpes Virus-6 (HHV-6)

What is human herpes virus (HHV-6)?

Human herpes virus 6 (HHV-6) is a virus that infects almost everyone, usually in childhood. HHV-6 causes roseola, a common illness in young children. Its symptoms include fever and rash. In most cases, children recover without medical treatment.

HHV-6 stays in your body for life. After infection, the virus stays “asleep” and doesn’t cause problems. However, if your immune system is weak, the virus can sometimes become active and cause illness. This is known as reactivation. Patients who have had a stem cell transplant are at higher risk for health problems due to HHV-6.

What are symptoms of HHV-6?

Signs and symptoms of HHV-6 may include:

  • Fever
  • Rash
  • Diarrhea
  • Liver problems
  • Low blood counts

HHV-6 can sometimes cause serious health problems in patients with weak immune systems. Complications of HHV-6 include low blood counts, pneumonia, graft versus host disease (GVHD), and encephalitis (swelling of the brain).

Encephalitis is rare but can be serious. Some signs are:

  • Confusion
  • Sudden fever
  • Drowsiness
  • Seizures
  • Memory problems
  • Severe headache
  • Vomiting

How do you test for HHV-6?

Doctors can do a blood test to look for the virus. The virus can affect the liver, brain, lungs, heart, kidneys, stomach, or intestines.

If your child’s health care team suspects HHV-6, they may do some tests. For example, symptoms like fever and rash may lead doctors to order an “HHV-6 PCR” blood test. This test shows if there is HHV-6 in the blood and how much virus is present.

If a patient shows signs of encephalitis, doctors may do a lumbar puncture to test the cerebrospinal fluid for HHV-6. An MRI scan may be used to look for brain swelling.

HHV-6 and Stem Cell Transplant  

Transplant patients are at higher risk for illness due to HHV-6 infection.

HHV-6 may become active after a stem cell transplant and cause health problems that affect recovery. HHV-6 can affect the brain, heart, lungs, kidneys, stomach, and intestines.

A healthy immune system usually keeps HHV-6 from causing problems. During a stem cell transplant, a patient receives treatments that weaken the immune system. This is called immunosuppressive therapy. It involves high doses of chemotherapy and other medications. Immunosuppression therapy helps keep the body from rejecting a transplant. During this time, HHV-6 may cause sickness.

If a patient has symptoms, doctors may use lab tests to check for HHV-6 infection. Your doctor may recommend treatment based on the test results.

How is HHV-6 treated?

Your doctor may prescribe medicines to fight the virus, called antivirals. Medicines used to treat HHV-6 include ganciclovir, valganciclovir, or foscarnet. Your child's BMT and infectious disease teams will decide what treatments are needed.

Key Points

  • Human herpes virus-6 (HHV-6) is a common virus that infects almost everyone, usually in childhood.
  • Patients are at higher risk for problems due to HHV-6 after a bone marrow transplant.
  • When HHV-6 becomes active, it can cause both minor symptoms and serious health problems.
  • If your health care team suspects HHV-6, they may do tests.
  • Your doctor may prescribe antiviral medicines, depending on test results.

If you have questions about HHV-6 or your child’s immune system, talk to your child’s doctor or nurse.

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Reviewed: July 2022