Figure 1. . . Age distribution by 4-month interval of 3,667 children admitted to Children’s Hospital 1, Ho Chi Minh City, Vietnam, who had clinical diagnoses of hand, foot, and mouth disease, September 18–November 30, 2011. White bars indicate total number of cases; black bars indicate severe cases (grade 2b or worse). Severe cases are defined as grade 2b, 3, or 4 disease.