Pathogens

Human Herpesvirus 6 – Infection, Transmission & Diseases

Human Herpesvirus 6

The human herpesvirus 6 , called HHV-6 for short , belongs to the herpesvirus family , which is divided into an alpha, beta and gamma subfamily. HHV-6 belongs to the beta herpesvirus subfamily, which has a very narrow host range and is slow to replicate in the body. The virus can cause various diseases in humans, but it can also survive in the body without any symptoms.

What is Human Herpesvirus 6?

A total of eight human pathogenic herpesviruses that can cause disease in humans have been characterized to date. HHV-6 has two subtypes, subtype A and subtype B. The virus was discovered in 1986 and is a double-stranded DNA virus. HHV-6 infects CD4+ T lymphocytes, specific cells of the human immune system .

The virus spreads via saliva and droplet infection . HHV-6 is distributed worldwide and is very common: more than 90% of adults carry the virus. The infection occurs from the sixth month of life, usually in infancy or early childhood. Before the sixth month of life, the infants are still through thematernal Antibodies that they picked up from the placenta before birth to fight infectionprotected.

Around 80% of children between the ages of two and five are already infected with the virus. If a pregnant woman is first infected with HHV-6, it can be transmitted to the embryo, so that the child carries the virus at birth.

Meaning & Function

Infection with the human herpesvirus 6 usually proceeds without clinical symptoms after the initial infection. HHV-6 remains latent in the body, which is a characteristic of all herpesviruses. Most adults are therefore mostly unaware that they are infected with the virus.

Complete elimination is usually not possible. When the virus is first infected, it can be detected in the blood, saliva and stool in the laboratory. It comes to the disease of the lymphatic system and the central nervous system . Because the virus can spread along nerve fibers, bypassing the blood-brain barrier, it enters the spinal cord and brain .

Here it infects glial cells and neurons. In the latent phase, HHV-6 is found in the salivary glands , through which it is excreted and disseminated. In this phase, the virus does not produce any particles that are infectious for the body. However, it can be reactivated and re-enter the infection cycle. This can happen especially with a weakened immune system. In immunocompromised patients who have an HIV infection or whose immune system is suppressed due to transplantation, there can be an increase in virus replication.

If the virus is reactivated, this can be expressed in the recurrence of the same or similar symptoms as with the initial infection. HHV-6 has different pathogenic mechanisms: The virus can lead to degenerative changes in cell morphology in infected cells (cytopathic effect). It can induce so-called cytokines, certain proteins that are responsible for cell growth and differentiation. HHV-6 can affect immune function by partially suppressing it. In addition, the virus can lead to trans-activation of other viruses in the event of co-infection.

Diseases & Ailments

The human herpesvirus 6 is mainly known as the causative agent of the three-day fever . This usually occurs in early childhood. After several days of high fever , a characteristic rash appears as the fever subsides .

Three-day fever heals by itself and is rarely associated with complications, so that therapy is usually not necessary. In Europe, it is usually triggered by subtype B of HHV-6. In individual cases, the disease can also occur in adults and manifests itself in flu – like symptoms. In rare cases, complications such as diarrhea and vomiting can occur. In addition, the eyelids and lymph nodes in the neck may swell, papules may appear on the palate and uvula, and febrile seizures may occur.

Various other diseases suspected to be related to HHV-6 infection have also been observed in very rare cases. HHV-6 can trigger a chronic fatigue syndrome that is associated with severe tiredness and exhaustion as well as depression . However, this probably affects less than 1% of all HHV-6 infected people. Inflammation of the heart muscle , pneumonia or hepatitis is also possible.

Conditions such as meningitis and encephalitis have also been observed. In addition to other factors, HHV-6 could have an impact on the development of multiple sclerosis. Researchers also suspect that HHV-6 can promote the development of basal cell carcinoma and squamous cell carcinoma as an additional factor . If HHV-6 causes severe complications, antiviral therapy can be carried out.

Lisa Newlon
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Hello! I am Lisa Newlon, and I am a medical writer and researcher with over 10 years of experience in the healthcare industry. I have a Master’s degree in Medicine, and my deep understanding of medical terminology, practices, and procedures has made me a trusted source of information in the medical world.