(HealthDay News) -- Fifth disease is a viral illness that primarily affects young children who attend school.

Caused by the human parvovirus B19, it's generally a mild illness but it can be extremely harmful to a fetus if a pregnant woman becomes ill with the disease.

The U.S. National Library of Medicine lists these common symptoms of fifth disease:

• Cheeks that are extremely bright red in color it looks like they've been slapped.
• A red, "lacy"-patterned rash that starts on the cheeks, eventually moving to the arms and legs.
• A fever.
• Pain in the joints.
• Anemia that's only temporary.