Prince George’s County’s fourth case of the coronavirus, which was announced Wednesday, is the state’s first community transmission, according to a tweet from Maryland Gov. Larry Hogan.

In other words, the individual who tested positive for the virus, a Prince George’s County resident in his 60’s, hasn’t traveled internationally recently, and hasn’t come into contact with another person known to be infected.

The community transmission case means Maryland is “entering a new phase of working to mitigate and limit the spread of this pandemic,” Hogan wrote in a news release.

Although there are four confirmed COVID-19 cases in the county, there are no confirmed cases on the University of Maryland’s campus, officials said Wednesday. Classes continued Thursday, as officials worked to sanitize at least two buildings where concerns about potential exposures arose.

Several professors and students who worked in Knight Hall attended a journalism conference last week where an individual tested positive for coronavirus and recently began self-isolating, although none of them are currently exhibiting symptoms, according to an email from journalism school dean Lucy Dalglish. Parts of the building were being cleaned intensely Wednesday night, and Dalglish announced that all in-person journalism classes would be canceled beginning at 11 a.m. Thursday. The building, however, remains open.

Officials announced that employees who work in the other building, the Manokin building, which is located in the Discovery District near the main campus, should not report to work on Thursday, as the building was being cleaned while an individual who worked there was awaiting coronavirus test results.

The virus, a respiratory disease that is particularly deadly for older people and those with compromised immune systems, is rapidly spreading across the state and the country. Currently, there are 12 confirmed cases in Maryland — in addition to the four in Prince George’s, there are six in Montgomery County and one each in Baltimore and Harford counties.