Infectious erythema, also called fifth disease, is a viral infection of the skin. The incubation period of this disease is usually 5-14 days, and the onset of the disease is usually sudden, usually without systemic symptoms, some people may only show mild fever or have sore throat and mild congestion in the throat. The first manifestation may be edema on both cheeks and the formation of fused erythema with butterfly-shaped distribution and clear borders. As the disease progresses, some people may develop well-defined, symmetrical, lace-like papules on the trunk, buttocks, and extremities, and sometimes on the palmoplantar area.