(a) If the boy is suffering from Typhoid, then, he should have sustained high fever (39° to 40°C), weakness, stomach pain, constipation and headache. So It cannot be typhoid.
(b) If the boy is suffering from Viral Fever he will suffer from high fever, joint pain, weakness, and headache, So It cannot be Viral Fever.
(c) If the boy is suffering from Malaria he should have high fever recurring with profuse sweating every three to four days associated with chills and headache. There is a possibility that he is suffering from Malaria because high fever associated with chills is possible with malaria.