hello..due to viral, bacterial and protozoan infection platelet count generally decreases. you have not mentioned the reports regarding total leukocyte count, , hemoglobin and pcv..my advice is wait for 2 days.repeat the cbc again.see whether ur child having pain abdomen and vomiting or not..these are danger signs of dengue.give paracetamol when fever comes and more fluids to your child.  if the report after 2 to 3 days decreases rapidly to 1 lakh then go for the dengue ns1 antigen and igm antibody test . hope I answered your query..