Fifth disease, also known as erythema infectiosum, is a mild viral infection caused by the parvovirus B19. It primarily affects children and is characterized by a distinctive red rash on the cheeks, often described as a "slapped cheek" appearance. The rash may spread to the body and limbs, and symptoms can include mild fever and fatigue. The disease is usually not serious and resolves on its own within a week or two. It is spread through respiratory droplets and is most contagious before the rash appears. Once the rash develops, individuals are generally no longer contagious.