MILWAUKEE — Officials have identified seven people who appear to have contracted the coronavirus through activities related to the April 7 election in Wisconsin, Milwaukee's health commissioner said, and advocates worry that they could be just the "tip of the iceberg."

Commissioner Jeanette Kowalik said six of the cases involve Milwaukee voters and one involve a Milwaukee poll worker, the Milwaukee Journal Sentinel reported.

Officials hope to have additional information on the cases by the end of the week, including whether any of them were concentrated in any of the city's five polling places or whether any resulted in death, Kowalik said Monday.

Wisconsin proceeded with in-person voting only after a bitter partisan fight. The state's Democratic governor tried to shift the election to vote-by-mail and postpone it, but he was blocked by the conservative majorities on the Wisconsin Supreme Court and in the Republican-controlled Legislature, prompting the chairman of the state Democratic Party to warn that voters would die as a result.

Now, Wisconsin Democrats worry that there may be more yet-to-be-reported cases, because Milwaukee officials say they have only about 30 percent of the data in yet and officials in other parts of the state have yet to release information on Election Day-related infections.

"I fear this is just the beginning," Democratic state Sen. Dave Hansen told reporters on a conference call Tuesday.

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In Florida, one of the last states to hold in-person voting before lockdowns went into effect in mid-March, at least two poll workers later tested positive for COVID-19.

Still, state Health Services Secretary Andrea Palm said Monday that there were no signs yet of a surge in cases from the election, as some feared. Palm noted, however, that if cases do exist, symptoms may not have appeared yet.

Tuesday marks the 14th day since the election, which is a time frame during which health officials say symptoms typically appear. The coronavirus causes mild or moderate symptoms for most people, but for some, especially older adults and people with existing health problems, it can cause more severe illness or death. To date, 230 people have died in Wisconsin, and nearly 4,500 have tested positive.

Advocates of voting by mail say Wisconsin's experience should be a warning to other states as the country grapples with how to hold an election during the pandemic.

"This was entirely preventable, but now Wisconsinites are paying a real price for the reckless disregard for their safety," said Sean Eldridge, who runs the liberal advocacy group Stand Up America. "If Congress fails to provide states funding for vote-by-mail and other election assistance, then what we're seeing in Wisconsin right now could be the tip of the iceberg."

Sen. Amy Klobuchar, D-Minn., who has been pushing Congress to make an expansion of voting by mail a part of the next coronavirus aid package, said the infections are a warning and suggested that President Donald Trump's objections to voting by mail are disingenuous.

"The tragic news of these cases in Milwaukee is further evidence of the immense public health crisis created when officials refuse to expand voting options so that Americans can safely cast a ballot," Klobuchar said. "While those voters were standing in line risking their lives, the President was at home requesting a mail-in ballot. We need to plan for November, which is why we need to pass my legislation that will guarantee every voter access to a mail-in ballot and expand early voting to help voters avoid crowds and long lines."

Alex Padilla, the secretary of state of California, where about two-thirds of ballots are now cast by mail, called news of the infections "infuriating."

"These voters risked their health to be able to cast a ballot. They never should have been forced to make that choice," he said on Twitter.

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Voters who went to the polls in Milwaukee stood in long lines, many for several hours, to cast their ballots. Many had no protective gear. And thousands of Wisconsin voters stayed home, unwilling to risk their health and unable to be counted because absentee ballots they had requested never arrived.

But Judd Choate, the director of elections in Colorado, one of five states that vote entirely by mail, said he saw a silver lining in Wisconsin's ability to dramatically scale up absentee mail balloting.

States across the country are expecting a surge in demand for absentee ballots from voters who want to avoid the polls during the crisis, and Judd said Wisconsin showed it's doable, even if it wasn't pretty.

"They went from almost no vote-by-mail to over half vote-by-mail in a couple of weeks," Choate told reporters on a call organized by the National Vote at Home Institute. "Yes, there were lines. Yes, there were these odd circumstances of people wearing masks and standing a great distance apart from each other. But that's the in-person part. The vote-by-mail part actually went pretty well."

There were still issues with the vote-by-mail part, including about 9,000 ballots requested by voters that were never sent. But the state still managed to process and count about 1.1 million absentee ballots, a more than fourfold increase from previous similar elections.

"I know there was a lot of concern about what happened in Wisconsin. I was actually encouraged," Choate said.