Gov. Charlie Baker made an appeal Saturday for Massachusetts residents to donate blood, calling it a way to save lives as the state strives to prevent its health care system from becoming overwhelmed by the pressures of the coronavirus pandemic.

The visit Baker made alongside First Lady Lauren Baker to the Red Cross donation center in Dedham was his first media appearance since Public Health Commissioner Dr. Monica Bharel announced Friday night she had tested positive for COVID-19. Bharel said she was experiencing mild symptoms and would work remotely while recuperating at home.

Baker on Saturday described Bharel as a "rabid distancer" who stayed apart from others. He said he and Bharel had not been in the same building in about a week, and that he was not among the close contacts whom health officials reached out to after Bharel received her test results.

He again said that he had not been tested for the virus because he is not experiencing symptoms. When the Bakers had their temperatures checked before giving blood Saturday, his was 97.7 degrees, the governor said.

The pre-donation temperature check is one precaution Red Cross officials said they are taking to ensure safe donations, along with social distancing efforts among donors and between donors and staff.

Lauren Baker, who serves on the board of directors for the Massachusetts region of the Red Cross, said hundreds of blood donations need to be collected each day to meet the needs of Massachusetts hospitals.

"If you're healthy and you want to do it, please don't be afraid," she said. "Please make an appointment. Please donate blood. Every effort helps."

Potential donors can visit the American Red Cross's website, fill out a questionnaire and, if they qualify, set up an appointment at a local donation site. Anyone who has traveled to China, Iran, Italy or South Korea, or had contact with a person who has the coronavirus, will be asked to postpone their donation for 28 days.

With most workplaces, schools, community centers and other places that would typically host blood drives now closed, Holly Grant, CEO of the American Red Cross of Massachusetts, said there are 300,000 units of blood that have gone uncollected nationally because of the coronavirus. Each unit of blood can save up to three lives.

In Massachusetts, she said the number of uncollected donations "is hovering between" 5,500 and 6,000.

"But as we move forward, we know that there are going to be less people who are going to be able to donate because of the coronavirus, so we're working really hard to ensure and invite those people who are healthy to come out and donate, because we know that we're going to be in this situation now for weeks and months to come," Grant said.

Saturday marked the 19th day of a state of emergency that Baker declared around the coronavirus. As of Friday afternoon, there were 3,240 confirmed cases of COVID-19 in Massachusetts, including 35 deaths and at least 288 people who had been hospitalized.

Baker said that the steps the state has taken over the last few weeks -- unprecedented measures like ordering the closure of schools and non-essential businesses and advising residents to stay in their homes -- have been made with two goals in mind.

First, he said, is to "try to keep people apart from one another to the fullest extent that we possibly can" to slow the spread of the highly contagious disease. The second is to stretch out that spread over a longer period of time, in hopes of keeping it within the capacity of the state's health care system.

In hard-hit countries like Italy, Baker said, people with "solvable and curable" medical conditions didn't get what they needed because the system was overwhelmed.

"You are, in many respects, by donating blood making it possible for the health care system to deliver for people who have conditions and illnesses and circumstances that are eminently treatable if the supplies are there and the capacity's there to serve them," he said. "I mean, this really is a way for people to save lives, and it's pretty much as simple as that."