Human Herpesvirus 6 (HHV-6)

Human herpesvirus 6, also called HHV-6, is most likely in your body right now, hanging out and not doing much of anything. If you're part of a certain minority, though, it may be causing one or more illness.

As the name suggests, HHV-6 was the sixth member of the herpes virus "family" to be discovered. Other herpesviruses include the Epstein-Barr virus, cytomegalovirus, and herpes simplex one and two, both of which can cause cold sores and sexually transmitted genital herpes.

All of the herpes-family viruses stay in your body for life, usually lying dormant. That means even if you have HHV-6 in your body, it's most likely not active or causing symptoms the majority of the time.

Symptoms are most likely when you first become infected; however, it is possible for the virus to reactivate at some point down the road. In that case, it may cause health problems including any of several neurological conditions.

HHV-6 can target the nervous system, which is made up of your brain and spinal column, the immune system, and a wide variety of organs.

It comes in two types, called A and B. Scientists originally thought they were variants of the same virus, but now they believe them to be completely separate from each other. HHV-6 A is rare and is usually found in adults, while the B type generally infects children.

HHV-6 B is the more common one. Most of us—more than 90 percent—are infected during our first three years and therefore carry it around with us for the vast majority of our lives. For most babies, the initial infection doesn't cause any noticeable health problems.

In about 20 percent, however, HHV-6 B infection causes a condition called roseola. Symptoms of roseola generally come in two stages. The first may include:

• Sudden high fever (above 103 F) lasting three to five days
• Mild sore throat
• Runny nose
• Cough
• Swollen lymph nodes in the neck
• Irritability
• Mild diarrhea
• Decreased appetite
• Swollen eyelids

Within a day of the fever going away, the child may develop a rash that doesn't itch or cause discomfort. The rash is made up of lots of small pink spots or patches, some of which may have a white ring around them. It will usually begin on the torso and then spread to the limbs and possibly the face. It can go away in as little as a few hours or hang around for several days.

Roseola usually isn't serious, but in rare cases, a child may develop a high fever that can lead to complications, including seizures. The typical treatment is medications to control the fever, and rest.

In addition to fever-induced seizures, HHV-6 B has been linked to epilepsy—a chronic condition featuring seizures—and encephalitis (inflammation of the brain), which can be fatal. Symptoms of epilepsy can vary and may involve any of the processes coordinated by the brain. Common symptoms include:

• Uncontrollable jerking movements
• Temporary confusion
• Staring off into space for a short time
• Fear and anxiety
• A sense of deja vu
• Loss of consciousness
• Loss of awareness

Epilepsy is chronic, meaning that it's a condition that requires long-term treatment and management.

Encephalitis may cause numerous symptoms, including:

• Seizures
• Headaches
• Muscle or joint pain
• Fatigue
• Weakness
• Fever
• Confusion
• Partial paralysis
• Speech problems
• Hearing problems
• Loss of consciousness

In babies and young children, it may also cause:

• Bulging in the skull's soft spots
• Nausea
• Vomiting
• Stiffness
• Irritability
• Poor feeding
• Sleeping through feeding times

If you suspect a child in your care has encephalitis, it's imperative that you seek immediate medical attention. Any kind of seizure also warrants urgent treatment.

Research links HHV-6 A to numerous neurological conditions. Some of these links are supported by considerable evidence, while other ties are less certain. At this point, we can't say for certain that HHV-6 directly causes any of these conditions.

While anyone can have an HHV-6 reactivation, it's most common in people with an immune system that's compromised by illness or medication. That includes those with HIV/AIDS, autoimmune disease, or organ transplants.

Diseases linked to HHV-6 reactivation are many. For most of them, though, we don't know if HHV-6 is the actual cause. These diseases include:

• Autoimmune disease: Hashimoto's thyroiditis, Sjogren's syndrome, lupus, multiple sclerosis, Guillain-Barre syndrome
• Bone marrow suppression
• Cancer: Hodgkin lymphoma, gliomas, cervical cancer
• Chronic fatigue syndrome (also called myalgic encephalomyelitis or ME/CFS)
• Cognitive dysfunction such as delirium, amnesia
• Colitis
• Encephalitis
• Endocrine (hormonal) disorders
• Epilepsy
• Heart disease: myocarditis, arteriopathies, left ventricle dysfunction
• Hypersensitivity: Stevens-Johnson syndrome, negative reactions to drugs
• Kidney disease
• Liver disease: hepatitis, HIV/AIDS-related
• Lung disease­­­: organizing pneumonia, pneumonitis
• Sarcoidosis

Some people with an active HHV-6 infection may develop more than one of these illnesses. However, a vast majority of people infected with this virus have no symptoms at all, and many have only mild, short-term symptoms.

We have a few different blood tests that can detect whether you're infected with HHV-6. One of the tests comes back with a "yes" or "no" answer, though, which isn't terribly useful. Remember that most of us have probably carried this virus around since childhood.

Instead of looking at whether it's there, another test looks at the level of antibodies in your blood, since an elevated number can indicate an active infection rather than a latent one.

Complicating matters is the fact that getting a negative result from a blood test doesn't necessarily mean you don't have an active infection. That's because HHV-6 can infect a single organ, including the brain, heart, lungs, liver, and uterus. That means tissues have to be tested to determine whether you're infected.

With blood tests being rather unreliable, doctors sometimes diagnose an HHV-6 reactivation based on symptoms. They also need to rule out other potential causes of similar symptoms, such as mononucleosis, which is caused by Epstein-Barr virus. Before diagnosing roseola in a baby, doctors generally consider other possible causes of rash and fever—of which there are many.

Your doctor may also use diagnostic imaging, tissue biopsy, lumbar puncture, or a method of visualizing the inside of your airways that's called bronchoscopy.

Different lab test are used for diagnosing HHV-6 reactivation in organ transplant recipients or people with hepatitis, encephalitis, or compromised immune systems.

At this point, we don't have a well-established treatment regimen for active HHV-6 infections. Because symptoms can vary widely from one person to another, doctors generally tailor the treatment to the individual case.

Antiviral drugs have gotten some attention for treating HHV-6, but so far, they remain unproven. Some of the more common drugs suggested for combating this virus are Cytovene (gancilovir) and Foscavir (foscarnet).

Sometimes, an infected baby may need to be hospitalized for treatment, but this is rare.

We do not have a vaccine for preventing HHV-6.

If you think you may have an illness that could be related to an HHV-6 infection or reactivation, be sure to bring it up with your doctor. A proper diagnosis is the first step toward finding the treatments that help you feel better.

Many of the illnesses linked to HHV-6 are chronic, so you may have to learn to manage them. Educating yourself, working with your doctor, and exploring different treatment options are all important when it comes to finding your optimum treatment regimen.