A 26-year-old man was diagnosed with coronavirus in Sylhet sadar upazila, raising the total number of confirmed cases in the district to four.   The patient is a resident of Tikorpara area in Khadimnagar union of sadar upazila.   Doctor Anisur Rahman, assistant director of Sylhet divisional office of Directorate General of Health Services (DGHS), said that the man’s sample tested positive at Sylhet Osmani Medical College Hospital and he is in isolation at his house.   Besides, three coronavirus patients, who are undergoing treatment at Sylhet Shaheed Shamsuddun Ahmed Hospital, are gradually improving, he added.