Hello Dengue fever is diagnosed when its pathogens present in blood film i.e. serology test . There develop decrease in platelets count . Normal platelet counts is 15000-450000 cmm . Usually in many diseases platelets also decreases as in malaria but recovers within a short period . As you mentioned that your son is having high grade fever 102-103 F ,so such high fever may be due to malaria and so decrease in platelets . So for this get in blood examination for malarial parasites . If malaria is positive and platelets are down ,need not to worry . Take simple treatment for malaria . In dengue first 5-6 days patient remains high ,while there after fever subside and patient feels intense headache and generalized body pain . Get in platelets examination ,if it comes If needed intravenous platelets are advised ,otherwise recover itself. Now a day DENGUE is not a big problem. Plenty of fluid and liquid diet with tylenol are sufficient. Good luck.