The first known positive case was more than a week ago. Since then, more than 28 employees have been infected. At least three people have been hospitalized.
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"This department won't give the members a work-from-home option. There's 150 people in the building who are affected by this, and they have to go into work every day," said Peter O'Brien, president of a local union for AT&T employees.
AT&T said that most employees are working from home, but some are required to report to work in person because of the sensitive nature of their duties.
"We provide our employees with the tools they need to stay safe on the job. Out of an abundance of caution, we have decided to temporarily close the building to protect the health and safety of our employees," AT&T said in a statement.
Employees are scheduled to return to work in a few weeks.
"I am very fearful for the members once they come back to work. I think the same situation will escalate again," said O'Brien.
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