It all started with cough 1 week before, Then next day he got fever. Next day he got fever, which remained for 2 day then 3rd day it started decreasing (while it was decreasing we consultant a doctor who gave paracetamol and antibiotics and suggested for covid-test, The covid test result was negative ) next one day the fever was mild and also had lose motion. But then 5th day onwards again the fever become severe and the body temperature was fluctuating frequently. And the condition remain same till date. What might be the cause of fever???