Four physicians and nine nurses of Thakurgaon Sadar Hospital were sent to home quarantine on Wednesday after a woman undergoing treatment at the hospital tested positive for coronavirus.   According to hospital sources, a pregnant woman from Dhaka got admitted to the hospital on April 14. She was suffering from fever and breathing problem.   Later, samples of the patient were sent to the PCR lab of Rajshahi Medical College Hospital on April 18. Test results came out positive on April 21 but the women was discharged from the hospital on April 19 and went to Panchagarh district.   Dr Nadirul Aziz Chapal, supervisor of Thakurgaon Sadar Hospital, said four doctors and nine nurses were sent to home quarantine.   Their samples were taken for coronavirus testing, he said.