Fifth disease is a contagious virus spread through blood or through the air by respiratory secretions, according to WebMD. It is mildly to moderately contagious and mainly affects children, although adults are also susceptible to the virus.
Fifth disease often starts with cold-like symptoms, including a fever, runny nose and headache, states the Centers for Disease Control and Prevention. Several days later, a rash often appears on the cheeks, with the possibility of additional rashes on other parts of the body. The primary contagious period occurs during the initial symptoms before the rash occurs. Most patients are no longer contagious once the rash appears.