In order to know the very early haematological changes which link closely with DIC of dengue haemorrhagic fever, haematological examinations at acute fever stage were performed on 52 children with unknown fever origin without haemorrhagic symptom. Serological examination on 30 cases revealed four cases of dengue virus (DV) infection, of which two were recent primary DV infection, and the other two were secondary. No haematological change was observed on the primary DV infected cases. However decrease of platelet counts (6×104/μl at acute fever stage, and 20×104/μl at 2 weeks after fever; 12×104/μl and 21×104/μl) and increase of factor VIII clotting activity (210%; 185%) were observed on the secondary cases, suggesting a participation of immunological mechanisms to the changes.
