What is the cause of roseola infantum?

Roseola infantum, also known as sixth disease, is primarily caused by human herpesvirus 6 (HHV-6) and, less commonly, human herpesvirus 7 (HHV-7). These viruses belong to the herpesvirus family and are typically responsible for the characteristic presentation of roseola, which includes a sudden onset of high fever followed by a distinct rash that develops as the fever subsides.

The nature of the causative viruses is critical for understanding the clinical manifestations and management of the condition. Since HHV-6 is the primary pathogen, it plays a significant role in the pathophysiology of roseola and is typically associated with the disease's typical progression, making this answer the correct choice.

On the other hand, the other options such as human herpes virus 5 (which refers to cytomegalovirus), varicella zoster virus (which causes chickenpox and shingles), and measles virus do not cause roseola infantum. These viruses are associated with different diseases and clinical presentations, highlighting the specificity of HHV-6 and HHV-7 in the context of roseola. This distinction is essential for accurate diagnosis and treatment in pediatric patients presenting with fever and rash.