Human betaherpesvirus 6B

HHV-6B genome map

Human betaherpesvirus 6B (HHV-6B) is a species of the Herpesviridae family, which is part of the Betaherpesvirinae subfamily. This virus is known to infect humans, and it is one of the two closely related viruses, the other being Human betaherpesvirus 6A (HHV-6A). HHV-6B is primarily known for causing the childhood illness exanthem subitum (also known as roseola infantum or sixth disease), characterized by sudden high fever followed by a distinctive rash as the fever subsides. However, its impact is not limited to childhood; it can also affect adults, particularly those with compromised immune systems, leading to more severe conditions.

Overview

HHV-6B is a DNA virus that shares many characteristics with other members of the Herpesviridae family, including its ability to establish latent infections in its host. After the initial infection, the virus can remain dormant in the body and can be reactivated under certain conditions, such as stress or immunosuppression. Reactivation of HHV-6B in adults can lead to conditions such as encephalitis, pneumonitis, and it has been associated with various other diseases, including multiple sclerosis, though the causal relationships are still under investigation.

Transmission

The primary mode of transmission of HHV-6B is through saliva, which can facilitate the spread of the virus within families and close communities. It can also be transmitted from mother to child during birth. The high prevalence of antibodies against HHV-6B in adults suggests that most people are infected in early childhood.

Clinical Manifestations

The most well-known clinical manifestation of HHV-6B infection is exanthem subitum, a mild childhood illness. The disease typically begins with a high fever that lasts for three to five days, followed by a rapid defervescence and the appearance of a rose-pink rash on the trunk and neck. In immunocompromised individuals, HHV-6B reactivation can lead to more severe diseases, including encephalitis, a potentially life-threatening inflammation of the brain.

Diagnosis

Diagnosis of HHV-6B infection is primarily based on the detection of viral DNA in blood, saliva, or other body fluids using polymerase chain reaction (PCR) techniques. Serological tests can also be used to detect antibodies against HHV-6B, indicating past or current infection.

Treatment

There is no specific antiviral treatment for HHV-6B infection. Management of the infection primarily involves supportive care to relieve symptoms. In cases of severe disease in immunocompromised patients, antiviral drugs such as ganciclovir, foscarnet, or cidofovir may be used, although their effectiveness specifically against HHV-6B is variable.

Prevention

Currently, there is no vaccine available to prevent HHV-6B infection. Preventive measures are generally aimed at reducing the spread of the virus through good hygiene practices and avoiding close contact with infected individuals, especially for those with weakened immune systems.