Roseola infantum is caused by ______
**Core Concept**
Roseola infantum is a viral exanthem that primarily affects infants and young children, characterized by a distinctive maculopapular rash following a high fever.
**Why the Correct Answer is Right**
Roseola infantum is caused by human herpesvirus 6 (HHV-6) and, to a lesser extent, human herpesvirus 7 (HHV-7). These viruses infect the T lymphocytes and other immune cells, leading to a viremia that causes the characteristic symptoms of roseola. The fever is thought to be a result of the immune response to the virus, and the rash appears as the virus begins to clear from the body.
**Why Each Wrong Option is Incorrect**
**Option A:** This choice is incorrect because roseola infantum is not caused by a rubella virus. While rubella virus can cause a similar rash, the clinical presentation and epidemiology of roseola infantum are distinct.
**Option B:** This choice is incorrect because measles virus causes a different type of rash and fever, typically accompanied by Koplik spots and a more severe clinical course.
**Option C:** This choice is incorrect because varicella-zoster virus causes chickenpox, a different viral exanthem with a characteristic vesicular rash.
**Clinical Pearl / High-Yield Fact**
Roseola infantum is often misdiagnosed as a common cold or another viral illness, but it can be distinguished by its high fever and characteristic rash. It is essential to recognize this condition to avoid unnecessary antibiotic treatment and to provide appropriate supportive care.
**Correct Answer:** D. Human herpesvirus 6 (HHV-6)