My sisterm18 ywars old, has high grade fever105 highest recorded for last 13 days,assosiated with chills and rigors.comes at 6 hr interval.subsided better with suppository rather than paracetamol. No history of visiting malaria endemic area,blood culture negative,no neutrophilic leukocytosis,no urinary tract infection, no pathology in chest xray,no gastro intestinal symptoms.. Pt has asthma and developed severw caugh for 4 days.didnt respond to oral antibiotic s.iv antibiotic 2 dose given.yet fecver is comung,
What can be the cause?