His wife Mira Bhattacharya, who also contracted the virus and is undergoing treatment at a city hospital, is also doing fine, they said.

The 77-year-old former CM, who is in home isolation and also suffers from chronic obstructive pulmonary disease (COPD), needs to go to the hospital for other clinical examinations, the sources said.

"But, he is not willing to go. Last night, his oxygen saturation slipped below 90; it improved after he was administered external support. We have urged him to go to hospital and get the tests done," one of the sources said.

Both Bhattacharya and his wife tested positive on Tuesday evening.