Dear Mr Dipak Kaul I am sorry to know your child is suffering from persistant high fever
. Ie appears most investigations have been done and the good news is those are all negative. I strongly advise you to take your child to your Doctor who may send the blood for culture. In the mean time I suggest to give the child plainty of fluid like electrol and paracetamol
syrup to take the tempareture down.In babies and children one of the cause of high tempareture is dehydration
. I wish your son gets speedy recovery. Kindest regards.