Children less than 5 years of age, hospitalised with acute GE, living in Singapore served by the hospital participating in the study (KK Hospital) (cases) and children who were born after 1 November 2005, aged at least 16 weeks and hospitalised for acute disease with non-GE causes in the same hospital, will be included in the study after matching them by date of birth (controls).

Inclusion Criteria:

Inclusion criteria for surveillance subjects

• A male or female child aged < 60 months at the time of admission (a child becomes ineligible on the day of its fifth birthday).
• Subject admitted with acute GE as an inpatient to the study site during the study period.
• Written informed consent obtained from the parent or guardian of the subject.

Selection criteria

For potential cases

Potential cases will be limited to those surveillance subjects:

• who are born after 1 November 2005 (date of availability of Rotarix™ vaccination in Singapore),
• who are aged at least 16 weeks at the time of hospital admission.

For confirmed cases

Confirmed cases will be limited to those potential cases

• whose stool samples are tested positive for RV by immunochromatographic test.

For controls

All controls must satisfy the following criteria at study entry:

• Admitted for acute disease with non-GE causes in the same hospital as the potential case.
• Born after 1 November 2005 (corresponding to the date of availability of Rotarix™ vaccination in Singapore).
• Aged at least 16 weeks at the time of hospital admission and matched with acute GE cases (potential cases) progressively by date of birth, within a range of ± 2 weeks from the date of birth of cases. In case there is no suitable match, then the range would be extended to ± 4 weeks.
• Written informed consent obtained from the subject's parents/guardians.

Exclusion Criteria:

For enrolment of surveillance subjects

The following criteria should be checked at the time of study entry. If any apply, the subject must not be included in the study:

• The diagnoses at admission to the study site do not include acute GE.
• Children for whom stool samples are not available up to 48 hours after admission.
• The onset of GE is after 48 hours of admission to the hospital (i.e. nosocomial GE).
• Children with a history of chronic and genetic diseases.

For selection of potential cases

In addition to the exclusion criteria for surveillance subjects, potential cases will not be selected if the following criterion applies:

• Subjects who had a previous episode of acute GE less than a week back i.e. recurrent GE episode.

For selection of controls

The following criteria should be checked at the time of study entry. If any apply, the controls must not be included in the study:

• Child who has symptoms of GE on the day of interview of his/her parent or guardian.
• The onset of GE occurs after admission at the hospital.