What is the small, single-stranded DNA virus known as the fifth childhood disease?

Parvovirus B19 is known as the fifth childhood disease because it causes a specific rash illness primarily in children, also referred to as "fifth disease" or "slapped cheek syndrome." This disease is marked by a distinctive facial rash that gives the appearance of slapped cheeks, often accompanied by mild fever and flu-like symptoms. Parvovirus B19 is a small, single-stranded DNA virus and is part of the Parvoviridae family. It commonly affects children during outbreaks in schools or daycare centers.

The other viruses listed have distinct characteristics and are associated with different diseases. Rotavirus is primarily recognized for causing gastroenteritis in children. Adenovirus type 40 also causes gastroenteritis, along with respiratory illnesses. Coxsackie A virus is known for hand, foot, and mouth disease, among other infections. Hence, Parvovirus B19's specific association with the distinct childhood rash and symptoms makes it the correct answer in identifying the virus known as the fifth childhood disease.