Roseola, also known as exanthem subitum or sixth disease, is a common and generally mild infection of early childhood. It is characterized by a sudden, high fever followed by a distinctive rash, typically resolving without complication. While the vast majority of cases occur in infants, adults can contract this illness, though it is a rare occurrence. Adult infection with the virus that causes roseola can present very differently than the classic childhood form and, in certain circumstances, may lead to serious health concerns. Understanding the difference between the typical childhood presentation and the atypical adult manifestation is important for recognizing this often-overlooked disease.
The Viral Cause and Typical Childhood Presentation
Roseola is primarily caused by Human Herpesvirus 6 (HHV-6), specifically the B-variant, with Human Herpesvirus 7 (HHV-7) occasionally being the culprit. Like all herpesviruses, HHV-6 establishes a lifelong, latent infection in the host after the initial exposure. The virus is globally distributed and highly infectious, which is why over 95% of the population tests positive for HHV-6 antibodies by adulthood.
The typical presentation in children, usually between six months and two years of age, begins with a sudden, high fever that can reach 104°F and lasts for three to five days. As the fever subsides, a characteristic rash of small pink spots appears, often starting on the torso before spreading to the limbs and face. This rash signals the end of the infection, and the child usually recovers completely within a week.
Adult Infection: Why Symptoms Are Often Atypical
Adults who contract a primary HHV-6 infection rarely present with the classic fever-and-rash sequence seen in infants. Instead, the illness often mimics other common viral syndromes, which contributes to its underdiagnosis.
The primary infection in adults is frequently described as a mononucleosis-like illness, characterized by symptoms such as persistent high fever, fatigue, and swollen lymph nodes. Inflammation of the liver, known as hepatitis, can also be a component of this initial adult infection. Because the symptoms overlap with those of Epstein-Barr virus (EBV) or Cytomegalovirus (CMV), HHV-6 is often not suspected or tested for.
A second way HHV-6 can affect adults is through viral reactivation. This occurs when the latent virus becomes active again. This reactivation is usually triggered by a temporary weakening of the immune system due to stress, a concurrent illness, or medical immunosuppressive therapy. In many healthy adults, reactivation may be entirely asymptomatic or result in only mild, non-specific symptoms. However, in individuals with compromised immune systems, reactivation can lead to serious and specific organ damage.
When Roseola Becomes a Serious Adult Concern
HHV-6 infection or reactivation is seen primarily in individuals with weakened immune systems. This high-risk group includes patients who have received solid organ transplants or hematopoietic stem cell transplants (HSCT), as well as those with HIV/AIDS. In these populations, the virus’s reactivation can lead to a variety of severe complications, which are rarely seen in healthy individuals.
Encephalitis, which is inflammation of the brain, is a serious outcome, and HHV-6 is a leading cause of viral encephalitis in HSCT recipients. Symptoms of encephalitis can include altered mental status, confusion, seizures, and profound memory loss. Reactivation can also target other organs, causing pneumonitis (lung inflammation), hepatitis (liver inflammation), and myelitis (spinal cord inflammation).
In transplant patients, HHV-6 reactivation has been associated with increased morbidity, delayed engraftment of bone marrow, and a higher risk of graft rejection. Due to the virus’s ability to remain latent in various tissues, it can re-emerge when the body’s immune surveillance is suppressed by necessary anti-rejection medications.
Diagnosis and Treatment
Diagnosing HHV-6 infection or reactivation in adults is often complicated because the symptoms are non-specific and mimic many other conditions. Diagnosis relies heavily on clinical suspicion, especially in high-risk patients, and is confirmed using laboratory tests that detect the presence of the virus itself. The most common method is using polymerase chain reaction (PCR) testing to find HHV-6 DNA in the blood or, for suspected brain involvement, in the cerebrospinal fluid (CSF).
Detecting HHV-6 DNA in the blood does not always signify active disease, as the latent virus can be present without causing symptoms. In mild or primary infections in otherwise healthy adults, treatment is generally supportive, focusing on rest, hydration, and fever reduction with over-the-counter medications. Specific antiviral medications are typically not required for these self-limiting cases.
However, for severe disease or complications, particularly in immunocompromised individuals, specific antiviral drugs are necessary. Treatment involves intravenous ganciclovir or foscarnet, administered for at least three weeks or until the virus is cleared from the blood and CSF. These medications require careful monitoring due to potential side effects on the bone marrow or kidneys.