hello,fever of your child is nothing but flu(fever caused by influnja virus)&unlikely to be suffering from maliaria,dengue,since 4days have passed off.duration of typical viral fever lasts usually7-10days(not exactily),during this period early fever is due to virus alone,later on bacterial fever replaces in most of cases(secondary bacterial),on&off usually common during first4 to5days inspite of best antibiotic priscerbied at this point.no antiviral druge for infunga viruses discovered for almost18 strains of this virus,''dummy medication works better than anything else at this period'' eg control temp by calpal syp alone, or else calpal with allerid syp,measured as per child wt,even then also on&off temp is commom until 4-5days,followed by best antibacterial treatment accordence with your treating pediatrician.nothing to worry,keep doing tipid spoing ta this time,otherwise child can develop convulsions,make sure that child hydriated by giving diluted milk,rice water&biscuit,bread etc.consult best pediatrician only.