A partner at the Vienna-based firm Wolf Theiss is seriously ill and hospitalized with the coronavirus, officially known as COVID-19, and three additional employees have tested positive.

In a statement on its website, the firm said that, upon learning on Thursday that one of its partners had tested positive for the coronavirus, it began testing all of its employees within 24 hours. On Friday, about 200 employees were tested, and another 80 were tested on Monday, it said.