Belgian health experts were due to meet on Friday after the country detected its first two cases of monkeypox, authorities said.
The cases were diagnosed in different cities, though Flemish broadcaster VRTNWS said both patients had attended the same party in an undisclosed location. Reuters could not immediately confirm this.
A leading virologist said the number of cases in the country would probably rise.
"I do expect more cases," said Steven Van Gucht from national public health institute Sciensano. As things stood, he was however confident that Belgium would be able to control the spread of the virus, he told Reuters.
The first infected person, diagnosed in Antwerp but whose place of residence was not reported, was not seriously ill and they and their partner were both in isolation, a spokesperson for Belgium's Agency for Care and Health said.
The second case was a man from the region of Flemish Brabant, a Leuven-based virologist, Marc Van Ranst, said on Twitter. That patient was also not seriously ill, according to Belgian media.
Monkeypox is a usually mild viral infection. Symptoms include fever, headaches and skin rashes.
Several cases have been detected in Britain - where authorities are offering a smallpox vaccine to healthcare workers and others who may have been exposed - and others in other parts of Europe.
Reporting by Charlotte Van Campenhout; editing by John Stonestreet
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