Fifth disease is caused by parvovirus B19, which is most likely transmitted through direct contact with saliva, sputum, or nasal mucus of infected people. It tends to affect children more than adults and is characterized by a rash that resembles a slapped cheek. Other symptoms of fifth disease include low-grade fever, chills, and body aches. Because medicines are not available to kill the virus, treatment consists of managing symptoms while the infection runs its course. Fortunately, the illness is usually mild among children and adults who are otherwise healthy.