Hundreds of Miami-Dade County Public Schools employees contracted COVID-19 from March through July.

The Miami Herald reports that the district has discovered exactly 578 cases since it began keeping data. With 40,000 employees, the Miami-Dade school district is the largest employer in the county. The nearly 600 confirmed cases is a severe leap from July, when the district reported only 100 confirmed cases.

Phyllis LeFlore, president of the American Federation of State, County and Municipal Employees (AFSCME) Local 1184—which represents the school district’s maintenance workers, bus drivers, and food service workers—says she discovered a little over a dozen sick people in her bargaining unit. That included two food service workers, three security guards, three employees in transportation, and no more than six custodians.

“They’re bringing it from home and they’re bringing it into the workplace,” she told the publication. “They’re not getting it from the school system.” LeFlore said she’s had to send home a whole staff because one person tested positive.

Last month, the teachers’ union revealed that at least one educator had died from the virus. Additionally, Al Palacio, the president of the union for Miami-Dade Schools Police Department, said seven police officers tested positive.

The Miami-Dade county schools chose to begin the new school year online with a start date of Aug. 31. School conditions will be revisited at the end of September, where it will be decided whether schools are safe to reopen for in-person learning by Oct. 5.