A DNC official said all speakers and presenters for the August 17-24 convention are now expected to speak from remote locations.
Wisconsin Governor Tony Evers, a Democrat, said Biden made the right decision.
"A lot has changed since we set out on this journey more than a year ago now, but the one thing that hasn't is Democrats' commitment to putting health and safety first," Evers said in a statement. "It has never been more important for elected officials to lead by example — that's the kind of leader Joe is, and that's the kind of president we need. I know he will continue to have a presence in Wisconsin, virtually or otherwise, and I look forward to doing everything we can to win Wisconsin."
Milwaukee Mayor Tom Barrett told reporters he learned of the decision early Wednesday in a phone call with the leadership team of the Democratic National Convention.
"I would be lying if I didn't tell you that I'm very, very disappointed in this, professionally and personally, because I think we all have had so much pride in having Milwaukee chosen to host the 2020 Democratic National Convention," Barrett said.
But Barrett, a Democrat, added that the higher priorities are public health, economic recovery and nation's reckoning on systemic racism. "I think all of us have to keep this in perspective," he said.
President Donald Trump has abandoned his own plans to accept the Republican nomination in person. On Wednesday, he mused about potentially making his acceptance speech from the White House.
Biden and Democrats for months have moved toward a virtual convention, first by delaying the convention from its original mid-July date to the week before Republicans' scheduled convention in Charlotte, North Carolina.
DNC officials later authorised organisers to plan for virtual proceedings, then added an explicit call for delegates not to travel to Milwaukee. More than 4000 delegates already were casting mail ballots for Biden's nomination and a platform that had been written and approved in meetings conducted online. But until Wednesday, it was expected that Biden and his running mate would speak from Milwaukee.
Biden is in the final days of deciding on a vice president, who he has said will be a woman.
Trump was far more reluctant than Biden to alter his convention plans, as he sought to downplay the pandemic's significance and push the country to return to normal operations. Trump jousted with North Carolina Governor Roy Cooper, a Democrat, because Cooper wouldn't guarantee the president that he'd lift restrictions on large public gatherings so that Trump could pack Charlotte's NBA arena.
Trump then said he'd travel to Jacksonville, Florida, to make his address, a decision welcomed at the time by Republican Gov. Ron DeSantis. Florida has since seen its Covid-19 cases spike, part of a national trend that led Trump to yield to public health experts and cancel the event.