An observational study of active case surveillance to identify the pathogens of clinically diagnosed HFMD cases aged 6 months to 18 years old recruited from puskesmas and hospitals in Indonesia.

Every time suspected case of HFMD presented to the hospital, the pediatrician will inform the patient to enroll in the study. After the subject signs the informed consent, the pediatrician will give the subject designated number to enroll to the study. After gathering general information, medical history, and physical examination, the eligibility of participants will be assessed. The subject that fulfills the eligibility criteria will be enrolled in the study. All participants will collect stool sample or rectal swab to be tested with PCR test for EV71, CA (planned serotypes 16/10/6). If the result is positive, the sample will be further tested with genotype sequencing of EV71 and CoxA. For subject with respiratory symptom, skin lesion or encephalitis, extra PCR testing will be collected for PCR testing. Blood sample will also be collected from all subjects. Only 20 subjects with positive PCR result that will be tested for SVNT and PRNT. Two weeks following participant recruitment, study staff will contact the participant by phone and document the outcome of the disease as well the subject's condition.

Inclusion Criteria:

• Clinically diagnosed HFMD children of either sex, aged 6 months - 18 years old in the study sites
• The participant's parent/ legally accepted representative (LAR) could understand and sign a documented informed consent voluntarily before the study procedures.

Exclusion Criteria:

• NA.

Participants with clinically diagnosed cases of HFMD will be enrolled during the epidemic season within one year or earlies.