A madrasha teacher died after showing flu-like symptoms at Sadar hospital here on Thursday afternoon.   The deceased aged about 61 was an assistant teacher of Sufia Darul Aman Islamia Dakhil Madrasha and a  resident of Charjangalia area of Kamalnagar upazila.   Dr Anwar Hossain, resident medical officer of Sadar hospital, said the man was a diabetic patient and had been suffering from fever, cold and respiratory problem for the last few days.   He went to Sadar hospital with respiratory problem on Wednesday and died on Thursday, said Dr Anwar. Samples were taken from the body and was sent for coronavirus   test, he said.   Mohammad Nurul Absar, officer-in-charge of Kamalnagar Police Station, said houses of 12 families in the area were put under lockdown following the death of the teacher.