Cosentini did not specify how large the proportion was. Scientific studies have shown an array of serious conditions in coronavirus patients but have yet to determine how widespread they are.
Bergamo was the first badly hit area in Europe, and the images of the outbreak were a shocking insight into how bad the pandemic could get.
Cosentini, who appeared in the video in March, told Sky News this week: "At first, initially, we thought it was a bad flu, then we thought it was a bad flu with a very bad pneumonia.
He added: "But subsequently we discovered that it is a systemic illness with vessel damage in the whole body with renal involvement, cerebral involvement. So we are seeing other acute manifestations of renal failure that require dialysis, or stroke, and then acute myocardial infarction, so a lot of complications or other manifestations of the virus."
The long-term health effects of the coronavirus are not known for certain, but several trends are emerging.
Respiratory problems are regularly observed, which can include acute respiratory distress syndrome, asthma, and what some doctors call "post-COVID lung disease."
The ICU at the Papa Giovanni XXIII Hospital said on July 8 that it finally had zero COVID-19 patients, more than four months after it received its first patient on February 23.
Bergamo is the worst-hit province in Lombardy, which is Italy's worst-hit region.
As of Monday, 16,748 people had died in Lombardy, making up 50% of Italy's total 34,954 deaths.
Authorities in Bergamo said on June 8 a study showed that more than 50% of people tested in the province have COVID-19 antibodies, according to Reuters .
Prosecutors in the province are investigating allegations of mistreatment, neglect, and wrongdoing by healthcare professionals.
And Italian health authorities are warning of a second wave.
"Although the lockdown measures made it possible to effectively control SARS-CoV-2 infection, widespread transmission of the virus persists when favorable conditions occur, causing outbreaks, including some of a significant size," the country's Ministry of Health said on Monday, according to the ANSA news agency .
"New cases of infection were diagnosed in almost all of the regions and autonomous provinces during the week of monitoring from June 29 to July 5, with an increase in cases with respect to the previous week in some areas," it added.