The Massachusetts Department of Public Health released new numbers for the cases of COVID-19 in the state Sunday afternoon with an increase of 15 potential cases from the previous day.

That brings the number of cases in the Commonwealth up to 28. One case is confirmed and the remainder are presumed positive.

All of the 15 new cases were tied to an annual international conference at the Boston Marriott Long Wharf of managers with the Cambridge-based biotech company Biogen on Feb. 26 and 27.

The cases included eight men and seven women including five from Suffolk County between 30 and 60 years old, five from Middlesex County between 40 and 60 years of age and another four from Norfolk County.

Twenty-three of the state’s 28 total cases are associated with the Biogen conference.

A woman of unknown age and residence was also among those being monitored, the DPH said in its press release, adding that all of the presumptive cases were isolating themselves at home.

The announcement came on the heels of a Friday press conference announcing five new presumptive positive cases including three associated with the Biogen employee conference, one case associated with international travel and a third that could not be linked to either factor.

At the conference, Baker said the risk to the general public "remains low," but state and city leaders said they are preparing for the number of cases to continue to grow in the coming days and weeks, according to State House News Service.

A spokesperson for Biogen told WGBH News that almost all of its approximately 2,400 Mass.-based employees are working from home until further notice.

"Biogen moved with a real sense of urgency," said David Caouette. "We knew the seriousness of the situation, and we contacted public health authorities as soon as we could."

Caouette said one of the Biogen employees who tested presumptive positive for coronavirus was among four Biogen managers who attended a March 2 conference at the Boston Marriott Copley Place with the Investment Bank Cowen and Company.

According to Caouette, Biogen and public health authorities are in touch with Cowen.

Cowen and the Marriott both did not immediately respond to requests for comment.