**Question:** Roseola infantum can be caused by -

A. Herpesvirus
B. Parvovirus
C. Streptococcus pneumoniae
D. Escherichia coli

**Core Concept:** Roseola infantum, also known as sixth sickness, is a viral infection primarily affecting infants and young children. It is caused by the human herpesvirus 6 (HHV-6), which is part of the Herpesviridae family, specifically the alpha-herpesviridae subfamily.

**Why the Correct Answer is Right:** Roseola infantum is caused by the HHV-6, which is a member of the alpha-herpesviridae subfamily. This virus infects the lymph nodes, spleen, and liver, leading to the characteristic clinical manifestations of roseola infantum. In most cases, the infection is self-limiting, but it can cause severe complications in immunocompromised patients.

**Why Each Wrong Option is Incorrect:**

A. Herpesviruses, including HHV-6, are known to cause viral infections, but the correct answer is specific to human herpesvirus 6 (HHV-6), not a general herpesvirus.
B. Parvovirus is unrelated to roseola infantum, as parvoviruses cause conditions like parvovirus B19 infection, which results in a different clinical manifestation.
C. Streptococcus pneumoniae is a bacterial pathogen responsible for conditions like pneumonia and meningitis, not a virus like HHV-6.
D. Escherichia coli (E. coli) is a common bacterium associated with urinary tract infections, diarrhea, and other gastrointestinal conditions, not a virus responsible for roseola infantum.

**Clinical Pearl:** In cases of suspected roseola infantum in young children, it is essential to consider the role of immunocompromised states in determining the severity of the disease. HHV-6 infection should be distinguished from other viral infections and bacterial pathogens. This knowledge is crucial for accurate diagnosis and appropriate management of the disease in pediatric patients.