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Human herpesvirus 6 (HHV-6) is a virus that is a member of the herpesvirus family. It has two subtypes—HHV-6A and HHV-6B. HHV-6B is the subtype that infects most children. In the United States, it’s estimated that 90% of kids get HHV-6 infections by age 2. HHV-6A is mostly an enigma—it’s unclear exactly what effect it has, if any, on human health. Like other human herpesviruses, HHV-6 can go into latency after the primary infection and reactivate later on in life. Other members of the herpes virus family include Epstein-Barr virus (EBV), cytomegalovirus (CMV), varicella-zoster virus (VZV), HHV-7, and the herpes simplex viruses (HSV-1 and HSV-2).
What are the signs and symptoms of HHV-6?
When a child is infected with HHV-6, they usually have a mild illness with a fever. Common symptoms HHV-6 causes include fevers in 60% of children, fussiness (70%), runny nose (66%), rash (31%), and diarrhea (26%) (Zerr, 2005). High fevers in these children can cause febrile seizures, but these are usually not dangerous.
One classic set of symptoms HHV-6 can cause is called roseola infantum. Roseola infantum is also known as sixth disease, exanthem subitum, or just roseola. It occurs in around 20-30% of HHV-6 infections, usually between 6 months and 2 years of age (Zerr, 2005). In roseola, young children have 3-5 days of high fever, followed by a widespread rash that first appears on the body.
Rarely, HHV-6 infections can cause serious inflammation of the lining around the brain (meningitis) and the brain itself (encephalitis). Meningitis and encephalitis can be life-threatening and require hospitalization and treatment. These serious infections are more common in children with poor immune systems, children with cancer, and transplant recipients.
How is HHV-6 transmitted? Can it be prevented?
HHV-6 is typically transmitted person-to-person via saliva (Miyazaki, 2017). Because there’s no vaccine for HHV-6, preventing HHV-6 infections is difficult. The best way to avoid HHV-6 infections is by practicing good hygiene, including frequent handwashing.
In transplant recipients, HHV-6 can go through reactivation and cause symptoms. Studies have shown HHV-6 associated with bone marrow suppression after transplantation (Zerr, 2005). This means HHV-6 can cause anemia and low levels of white blood cells and platelets, which can lead to fatigue, decreased immunity, and bleeding.
How are HHV-6 infections diagnosed?
HHV-6 infections in healthy children with normal immune systems are usually mild and don’t require lab testing. Healthcare providers will usually be able to diagnose HHV-6 infections based on the symptoms and physical exam. However, in children with poor immune systems or in severe, life-threatening cases of suspected HHV-6, lab testing for the virus might be necessary. The most commonly used test is the polymerase chain reaction (PCR) test in which samples are tested for the viral DNA. This test can detect HHV-6 in the blood, cerebrospinal fluid (CSF), brain, or lung.
Herpes: what you need to know about this family of viruses
What’s the treatment for HHV-6?
In healthy, immunocompetent children and adults, symptoms from HHV-6 viral infections usually get better on their own. Generally, drinking plenty of fluids, acetaminophen (brand name Tylenol), ibuprofen (brand name Advil), and maintaining adequate nutrition can help. Never give a child aspirin as it can cause a dangerous, life-threatening condition called Reye syndrome, which is marked by brain and liver swelling. If there’s a rare, serious infection, such as encephalitis (brain) or myocarditis (heart), IV antiviral medications may help. Your healthcare provider may choose ganciclovir or foscarnet to treat HHV-6.
Multiple sclerosis and HHV-6
Research into HHV-6 is still developing. Multiple sclerosis, in particular, has been linked to HHV-6. Multiple sclerosis (MS) is an autoimmune disorder that affects your central nervous system—your brain and spinal cord. In MS, your immune system attacks the protective sheath around your nerves. There’s a lot of variety in the clinical manifestations of MS—it can cause many different symptoms, including fatigue, loss of coordination, loss of vision, and pain. The severity of MS varies from person to person, but in some people, MS is chronic, progressive, and debilitating. A key feature of MS is the development of plaques (also known as lesions or scars) caused by repeated attacks by a person’s immune system against cells in their own nervous system. In these plaques, virology and infectious disease researchers have found HHV-6 DNA. In the peripheral blood of MS patients, these researchers have also found elevated levels of antibodies against HHV-6, which may indicate that the immune system is reacting against the virus as part of the MS disease process (Leibovitch, 2014). Other studies have found HHV-6 and HHV-8 in MS brain tissue (Merelli, 1997). Though much more research needs to be done, it’s possible that antiviral drugs may be developed in the future to help with MS.
Other research has linked HHV-6 reactivation to chronic fatigue syndrome (CFS), although this may reflect a difference in the immune systems of patients with CFS than HHV-6 being the culprit (Ablashi, 2000). Rare cases have also been reported of HHV-6, causing pneumonitis (lung infections) and liver infections (Olson, 2019).
- Ablashi, D. V., Eastman, H. B., Owen, C. B., Roman, M., Friedman, J., Zabriskie, J. B., et al. (2000). Frequent HHV-6 reactivation in multiple sclerosis (MS) and chronic fatigue syndrome (CFS) patients. Journal of Clinical Virology, 16(3), 179–191. doi: 10.1016/s1386-6532(99)00079-7. Retrieved from https://www.ncbi.nlm.nih.gov/pubmed/10738137
- Leibovitch, E. C. & Jacobson, S. (2014). Evidence linking HHV-6 with multiple sclerosis: an update. Current Opinion in Virology, 9, 127–133. doi: 10.1016/j.coviro.2014.09.016. Retrieved from https://www.ncbi.nlm.nih.gov/pubmed/25462444
- Merelli, E., Bedin, R., Sola, P., Barozzi, P., Mancardi, G. L., Ficarra, G., et al. (1997). Human herpes virus 6 and human herpes virus 8 DNA sequences in brains of multiple sclerosis patients, normal adults and children. Journal of Neurology, 244(7), 450–454. doi: 10.1007/s004150050121. Retrieved from https://www.ncbi.nlm.nih.gov/pubmed/9266465
- Miyazaki, Y., Namba, H., Torigoe, S., Watanabe, M., Yamashita, N., Ogawa, H., et al. (2017). Monitoring of human herpesviruses‐6 and ‐7 DNA in saliva samples during the acute and convalescent phases of exanthem subitum. Journal of Medical Virology, 89(4), 696–702. doi: 10.1002/jmv.24690. Retrieved from https://www.ncbi.nlm.nih.gov/pubmed/27648817
- Olson, C. A., Dominguez, S. R., Miller, S., Chiu, C. Y., & Messacar, K. (2019). Gastroenteritis, Hepatitis, Encephalopathy, and Human Herpesvirus 6 Detection in an Immunocompetent Child: Benefits and Risks of Syndromic Multiplex Molecular Panel Testing. The Journal of Pediatrics, 212, 228–231. doi: 10.1016/j.jpeds.2019.04.058. Retrieved from https://www.ncbi.nlm.nih.gov/pubmed/31208781
- Zerr, D. M., Meier, A. S., Selke, S. S., Frenkel, L. M., Huang, M.-L., Wald, A., et al. (2005). A Population-Based Study of Primary Human Herpesvirus 6 Infection. New England Journal of Medicine, 352(8), 768–776. doi: 10.1056/nejmoa042207. Retrieved from https://www.ncbi.nlm.nih.gov/pubmed/15728809
- Zerr, D. M., Corey, L., Kim, H. W., Huang, M. L., Nguy, L., & Boeckh, M. (2005). Clinical Outcomes of Human Herpesvirus 6 Reactivation after Hematopoietic Stem Cell Transplantation. Clinical Infectious Diseases, 40(7), 932–940. doi: 10.1086/428060. Retrieved from https://www.ncbi.nlm.nih.gov/pubmed/15824982
Dr. Mike is a licensed physician and the Director, Medical Content & Education at Ro.