What is Herpes Virus Type 6 (Roseola)?
The human herpesvirus 6 (HHV-6) was first found in the blood cells of adults with immune disorders or AIDS, and was initially known as the human B-lymphotropic virus. Further study found HHV-6 in specific immune cells known as CD4+ lymphocytes, and classified it as part of the herpesvirus family. Since it was the sixth of its kind to be discovered, it was renamed as human herpesvirus 6. Like all herpes viruses, HHV-6 can cause different types of infections, ranging from short-term to lifelong.
HHV-6 is a term used to describe two related viruses, known as HHV-6A and HHV-6B. These two are now classified as separate viruses within the herpesvirus family, instead of being considered different versions of the same virus. While not much is known about HHV-6A, it is normally found in people with weakened immune systems. On the other hand, research shows that HHV-6B is the cause of a common childhood illness called roseola infantum. HHV-6B is quite common in children and is often seen in emergency departments around the world. More than 90% people get HHV-6B within the first three years of their life, making it a widespread virus.
What Causes Herpes Virus Type 6 (Roseola)?
HHV-6A, HHV-6B, and HHV-6B share similarities with human cytomegalovirus (CMV), another type of beta-herpesvirus. Both HHV-6A and HHV-6B reproduce in T-cells, a type of immune cell. However, they use different receptors for this process. HHV-6A uses a receptor called CD46, whereas HHV-6B uses one named CD134, which is present only in activated T cells.
Like other viruses such as HHV-8, also known as the Kaposi sarcoma-associated herpesvirus (KSHV), and the Epstein Barr Virus (EBV), HHV-6 can cause cancer and destroy autoimmune cells. Once it attaches to its receptor, HHV-6 settles in lymphocytes (another type of immune cell) and can trigger both immune suppressing and chronic inflammatory responses.
By adulthood, over 95% of people have been exposed to HHV-6A, HHV-6B, or both. However, current testing methods can’t tell the difference between these two variants. It’s well known that HHV-6 is the primary cause of roseola in young children, a common sickness with high fever and rash. Furthermore, HHV-6B primarily affects infants and is often reactivated in adults, regardless of their immune status. Usually, adults with continuous HHV-6 exposure don’t display symptoms.
There is ongoing research regarding the role of HHV-6 in the nervous system. In one study, over 70% of children with primary HHV-6 infection had the viral DNA detected in their cerebrospinal fluid, or CSF (the liquid around the brain and spinal cord). These children experienced neurological symptoms, including recurrent fevers and seizures. However, other studies showed a 0% to 4% detection rate of HHV-6 DNA in the CSF of children with fever-related seizures and AIDS patients with neurological symptoms.
These viruses are connected to illness in patients with weakened immune systems and may contribute to diseases such as Hodgkin’s disease and other cancers. Furthermore, HHV-6A and HHV-6B have been identified as sources of opportunistic infections in patients with weakened immune systems, causing diseases like encephalitis, hepatitis, colitis, and pneumonia.
Risk Factors and Frequency for Herpes Virus Type 6 (Roseola)
The HHV-6B virus is known to cause most HHV-6 infections that come with symptoms. Although most people have had an HHV-6 infection at some point, this primarily happens in the first two years of their lives. In this age group, it usually presents as a feverish illness, but some kids may show the typical signs of roseola infantum, another disease. It has been noted that as age increases, the chances of having the virus decrease, meaning it’s more common in younger individuals. Although it is rare in adults, the virus can reactivate at any age in anyone, irrespective of their sex or race.
The HHV-6 virus is widespread globally. According to a large study in North America, kids between 6 and 9 months of age are most likely to contract the virus. The story is the same in the UK and Japan, where 97 to 100% of primary infections are due to the HHV-6B variant. On the other hand, the HHV-6A variant usually infects people later in life and often doesn’t show symptoms. However, some studies have found this variant in symptomatic kids from Africa and the USA, particularly in regions of sub-Saharan Africa where HIV is prevalent.
- The rate at which people carry the virus (seroprevalence) can vary greatly between different populations.
- In Morocco, 20% of pregnant women tested were found to carry the virus.
- In contrast, all asymptomatic adults tested in a Chinese study were carrying the virus.
- In a more broad range of adults from Tanzania, Malaysia, Thailand, and Brazil, the seroprevalence varied between 39 and 80%.
Signs and Symptoms of Herpes Virus Type 6 (Roseola)
Human Herpesvirus 6 (HHV-6) is associated with certain conditions, notably central nervous system diseases and diseases in people with weakened immune systems, including organ transplant recipients. Usually, an HHV-6 infection is harmless and clears up on its own. It is primarily seen in infants or adults with weakened immune systems who are having a reactivation of the virus.
A type of HHV-6, known as HHV-6B, causes a common childhood illness known as exanthema subitum or roseola infantum. This condition, which causes high fever and a mild rash, is a common reason for young children visiting emergency departments with a fever. HHV-6B is also the cause of the majority of fever cases in children 12 to 15 months old.
Roseola infantum is typically diagnosed based on its symptoms. Children often suddenly develop a high fever, sometimes accompanied by swelling around the eyes, pink eyes, or inflamed ear membranes. Others, meanwhile, may seem active and healthy. Other associated symptoms in children include enlarged lymph nodes, stomach issues, abnormal liver function, and bulging soft spots on a baby’s head (fontanelles). In adults, the symptoms are similar to those of encephalitis, and in transplant recipients, the symptoms may include fever, signs of organ rejection, lung inflammation, inflammation of the spinal cord, and rash.
On a physical examination, healthcare providers often find indications that align with the reported symptoms. After the child’s fever subsides, a characteristic red rash often appears on the skin. This rash, which usually lasts one to two days, is reddish-pink and raised, often with a halo around it. However, some cases involve fever without a rash. Signs of respiratory infections are common in children, while adults may exhibit fever, enlarged liver and spleen, and swollen lymph nodes.
Testing for Herpes Virus Type 6 (Roseola)
Human herpesvirus 6 (HHV-6) can be identified using various lab tests such as polymerase chain reaction (PCR), serology, or viral cultures. PCR is the most commonly used method. However, these tests are usually not done in people with healthy immune systems as the disease often resolves on its own. The virus most often lives in the saliva and can be spread through it. While it hasn’t been found to spread through blood transfusions or breastfeeding, there have been cases of it being spread through organ transplantation. Experts believe that one form of the virus usually appears early in life (HHV-6B), while another form appears later (HHV-6A). Both types can be found in adults, indicating that many people carry the virus for a long time.
Lab tests in people with HHV-6 could show increased or decreased white blood cell counts or anemia. People with kidney transplants or liver issues should also have tests done to check their kidney and liver function and to rule out problems with electrolytes and hepatitis.
The need for imaging tests depends on what symptoms the patient is experiencing. This is especially important in patients with weakened immune systems. Chest X-rays can be done to rule out conditions like pneumonia. Head CT scans can also be done to check for other diseases that can be treated. In cases where the virus is affecting the central nervous system, a lumbar puncture (a type of spinal tap) might be necessary. This condition often results in mild increases in cells and proteins in the spinal fluid. The fluid can be tested for HHV-6 to confirm the diagnosis.
Treatment Options for Herpes Virus Type 6 (Roseola)
At present, there’s no approved medication designated solely for the treatment of HHV-6, and there’s also no vaccine. Generally, experts advise against giving medication to prevent HHV-6 infection. Instead, quick treatment with antiviral drugs is recommended, particularly for cases involving brain inflammation caused by HHV-6. The first-line treatment usually involves intravenous administration of two drugs, ganciclovir and foscarnet, over a period of 3 to 4 weeks. For patients undergoing stem-cell transplantation, treatment with ganciclovir has been shown to be beneficial and is the recommended antiviral medication.
HHV-6 infections in children with a healthy immune system typically resolve on their own and don’t require treatment. When infants contract roseola infantum, a common illness caused by HHV-6, treatment usually involves managing symptoms. Medications like acetaminophen and ibuprofen are advised to alleviate high fever and prevent seizures due to high body temperature. If fever-induced seizures occur, epilepsy drugs are not necessary. However, individuals with HHV-6 infection who have symptoms involving the central nervous system, including fever-induced seizures, should be hospitalized for treatment.
What else can Herpes Virus Type 6 (Roseola) be?
When diagnosing a condition, doctors might consider a range of other diseases that share similar symptoms such as:
- Infectious mononucleosis
- Cytomegalovirus infection
- Hepatitis caused by a virus
- Herpes simplex virus infection
- Meningitis
- Rubella
- Viral pneumonia
- DRESS syndrome, which is a reaction to a drug that results in a rash and other symptoms.
In children, an illness called roseola infantum, which causes a fever and a rash, is usually caused by the HHV-6 virus. However, other diseases can cause similar symptoms, so doctors will need to rule these out too. In adults who have a healthy immune system, the HHV-6 infection has symptoms similar to mononucleosis. Therefore, even though the diseases are different, doctors need to ensure they are not dealing with mononucleosis or another disease, cytomegalovirus.
For patients with a weakened immune system, which includes organ transplant recipients and people with AIDS, the symptoms can be more severe, and they might also have cytomegalovirus in addition to HHV-6. It’s also been shown that people with HHV-6 could develop conditions like hepatitis, herpes simplex, meningitis, rubella, viral pneumonia, and DRESS syndrome. There’s even some evidence that HHV-6 has been seen in multiple sclerosis, encephalitis, and interstitial pneumonitis cases. In certain instances, HHV-6A has been linked to Hashimoto’s thyroiditis, a condition where the immune system attacks the thyroid.
What to expect with Herpes Virus Type 6 (Roseola)
Typically, the initial infection with HHV-6, a type of virus, is mild and doesn’t cause any lasting health issues for healthy individuals. However, in people with weakened immune systems, the illness can be more severe. There have been reports of lung inflammation, liver disease, and organ rejection among transplant patients. Unfortunately, some patients with brain inflammation linked to HHV-6 have passed away.
In a 2003 to 2004 Japanese study, patients with a specific rash-related brain inflammation due to HHV-6 had a particularly challenging recovery, with some fatalities reported. Particularly, two children who suffered fatalities from brain dysfunction linked to HHV-6 were found to have a hereditary disorder affecting their mitochondria, the energy-producing parts of cells.
Possible Complications When Diagnosed with Herpes Virus Type 6 (Roseola)
HHV-6 is a type of virus that generally causes a benign infection, clearing up on its own within 5 to 7 days. The most frequent problem related to this infection is known as roseola infantum, which can cause seizures triggered by high fevers. In some instances, the virus may have negative effects on the nervous system. This is particularly true in cases where the brain and central nervous system become affected, such as with meningoencephalitis and encephalopathy. This means that the virus can occupy the brain during the initial infection and may continue to stay dormant within the brain tissue. As a result, there have been reports of cases of sudden or gradual inflammation of the brain, sometimes linked with the breakdown of the protective sheath around nerve fibers, either in scattered patches or across a larger area. The HHV-6 virus can also cause infections in individuals with weakened immune systems, though this is rare. The activities of the two types of HHV-6 virus (HHV-6A and HHV-6B) have been observed after kidney, liver, and bone marrow transplants.
Potential Complications of HHV-6 Infection:
- Roseola infantum (commonly resulting in fever-induced seizures)
- Nervous system effects (such as meningoencephalitis and encephalopathy)
- Dormancy of the virus in brain tissue
- Sudden or gradual brain inflammation (sometimes linked with the breakdown of protective sheath around nerve fibers)
- Rare cases of infection in people with weakened immune systems
- Activity of the virus following organ and bone marrow transplants
Preventing Herpes Virus Type 6 (Roseola)
When a healthy baby has roseola infantum, it’s critical for parents to understand what to expect, which can help with any worry about fever or possible seizures caused by the fever. Parents should be informed about the importance of using medications to reduce fever, and told that antibiotics usually don’t help in such cases. For individuals who have a weakened immune system, it’s important to understand the more complicated symptoms and other viral illnesses that can come with a HHV-6 infection. They should be guided on the importance of seeking medical help early when they notice any symptoms.
