Dr Ahsan Habib, a doctor from Rangpur City Corporation's Jahaj Company area, had a fever and other Covid-19 symptoms for the past eight days.
But he did not stop seeing patients.
According to the civil surgeon's office and local sources, the doctor submitted his sample on June 2 and tested Covid-19 positive on the test report that arrived on Wednesday night.
Kamruzzaman Ibn Taj, chief health officer of Rangpur City Corporation, said: "His chamber was locked down on early Thursday."
Later, officials of the city corporation's health department went to his home and told everyone in the house to stay in quarantine.
And Dr Ahsan was sent to Rangpur Shishu Mangal Sadar Hospital for institutional isolation.
Although the doctor was supposed to stay at home in isolation after giving regular samples, he kept everything secret and led a normal life including visiting patients, going to the mosque and taking a walk outdoors regularly.
Even on early Thursday, he came to his chamber.
Locals complained about his actions and said, "We are very worried now."
"What he did was absolutely wrong being a doctor. And appropriate action will be taken against him," said Rangpur district's Civil Surgeon Dr Hirombo Kumar Roy.
Dr Ahsan Habib (MBBS) is a former associate professor of Rangpur Medical College Hospital and would see patients at Bata alley in the city's Jahaj Company area.