Karim Ibourki, a ministry spokesman, said on Saturday that the man was undergoing tests to determine whether he had contracted the H5N1 avian flu. He said results were expected later in the day.
There was confusion over the man's identity, with some officials saying he may be a journalist who had worked in Turkey covering the bird flu story, and others saying he was a holidaymaker.
Ibourki said the man had done some work in the eastern province of Van.
"He probably is a journalist who had gone to Turkey to cover the spread of the virus," he said.
Meanwhile, Inge Jooris, spokeswoman for the committee in charge of monitoring for any trace of bird flu in the country, was also unable to confirm his identity, saying he could be someone who had been a tourist in the province.
The hospital in Brussels where he was being treated declined
The man checked himself into the hospital on Friday after returning from Turkey on Thursday, Ibourki said.
He said the man was not a Belgian citizen, but was unable to provide more details.
Three children have died from bird flu and 15 others have been infected since the outbreak began in Turkey two weeks ago.
Hundreds of thousands of wild birds and poultry have been culled, and producers say that demand for poultry has fallen significantly.