((This April 21 story refiles to update last paragraph to clarify Oregon’s vote-by-mail system))

(Reuters) - At least seven people contracted the coronavirus during Wisconsin’s primary election on April 7, Milwaukee health officials said on Tuesday, confirming fears that holding in-person voting during the health crisis put people at risk.

The seven cases include six voters and one poll worker in Milwaukee, the state’s largest city, where nearly 200 voting locations were pared back to five and there were hours-long lines to cast ballots, the office of Milwaukee Health Commissioner Jeanette Kowalik confirmed.

The number of election-related infections could grow as the 14-day incubation period ends on Wednesday, health officials said.

As of Tuesday afternoon, Milwaukee had 1,697 confirmed cases of COVID-19, the respiratory disease caused by the new coronavirus, and 92 deaths related to the virus. Wisconsin had 4,620 confirmed cases and 242 deaths overall, according to city and state data.

Democratic Governor Tony Evers, who declared a state of emergency on March 12, tried to delay the April 7 election or move all voting to mail-in ballots. But courts sided with the Republican-controlled state legislature to hold in-person voting.

Democrats in the U.S. Congress have called for legislation to ramp up the use of mail-in voting, automatic voter registration and early voting in November’s general election amid coronavirus concerns.

President Donald Trump and many of his fellow Republicans oppose such measures. Trump has said that mail-in voting is “very dangerous” and can lead to fraud. He has acknowledged he cast an absentee ballot by mail last month in Florida’s Republican primary.

Election experts say that while there is more fraud in mail-in voting than in-person voting, election fraud remains rare overall.

Ohio will hold its rescheduled primary elections next week, with voting done mostly by mail. Kansas has canceled in-person voting for its May 2 primaries and moved to a mail-in system.

Nebraska, Idaho and Oregon are among states with primary elections in mid-May that so far are still scheduled to move forward. In Nebraska, several hundred thousand voters have already requested mail-in ballots, state election officials have said. Idaho will use absentee ballots. Oregon has an established vote-by-mail system.