Hi My Brother 38 Years Old Was Perfectly Well Until

Hi My brother 38 years old was perfectly well until one Sunday where he woke up feeling extremely tired.he took a lot of water and felt ok in the evening.but the following Thursday night he developed fever upto to today which is one week with fever.it goes down with paracetamol only for a while and then come back again.Has been to different Drs blood count is perfectly normal after checking twice in a space of 4 days.urinalysis and malaria negative.salmonella negative.he was still given antimalarial of which he finished the dose but still no improvement.please help