They surpassed the previous record of 263-5, set by Royal Challengers Bangalore in 2013
The former India captain's brother Snehasish said that the 49-year-old tested positive for the virus on Monday.
Cricinfo said the hospital declared Ganguly "clinically stable" and that he would "remain in home isolation".
One of India's most successful captains, Ganguly underwent an angioplasty at the start of the year after complaining of chest discomfort.
India reported 16,764 new COVID-19 cases on Friday, with the number of deaths rising by 220.
About 34.8 million people have contracted the novel coronavirus in the world's second-most populous nation with confirmed deaths of over 480,000.