Patients: All of the patients with DSS (grades III and grades IV) admitted at Paediatrics department of VinhLong general hospital from 2003 to 2004.Results: There were 143 patients with DSS admitted at Paediatrics department of VinhLong general hospital from 2003 to 2004, confirmed by possitive serum Mac-Elisa IgM antibody, including133 ones with DSS grades III and 10 ones with grades IV.