A man who was undergoing treatment at the isolation unit of Bangladesh Institute of Tropical and Infectious Diseases (BITID) died here on Sunday morning.   Civil Surgeon Sheikh Fazle Rabbi said the man aged about 56 of Sagarika area in the city came to the BITID on Saturday with cold, cough, fever and respiratory problem.   The authorities concerned of the hospital took his samples for test but the man died around 7:30 am at the isolation unit of the hospital.   Coronavirus so far claimed five lives in the district  and 35 people tested positive for the virus.