This study is a sero-survey study of infants aged 6 months to 71 months in Bandung City and West Bandung District. As initial data to find out how many children have been exposed to human enterovirus type 71 (HEV-71) which causes Hand, foot, and mouth disease (HFMD).

This study is a cross-sectional seroprevalence survey of EV-71, associated with HFMD, among children aged between 6 to 71 months in Bandung, sampled from urban and rural Primary Health Center in Bandung, Indonesia. This study was implemented by Department of Child Health Hasan Sadikin General Hospital/Medical Faculty Universitas Padjadjaran Bandung, West Java. Age-stratified sample of 600 children aged 6-71 months will be conducted from these sites. Samples testing includes routine blood counts, enzyme-linked immunosorbent assays (ELISAs) for enterovirus type 71 (EV71) IgG and ELISAs for other HFMD-associated enteroviruses.

Inclusion Criteria:

• Children aged 6 months to 71 months.
• The participant's parent/guardian receives an explanation and receives a Letter of Consent after the explanation (informed consent) and provided a documented informed consent by parents/legally accepted representative (LAR) participants prior to the study procedures.
• Domicile in Bandung and West Bandung District for at least 6 months.

Exclusion Criteria:

• Children with difficulty to withdraw the blood during blood collection
• Children with severe illness who require further treatment

The study population are children aged between 6 to 71 months in Bandung, sampled from urban and rural Primary Health Center in Bandung, Indonesia