Tuberculosis or TB is a contagious disease of the lung.
The transport company says that the travelling public should not have been in any danger because metro drivers are seated in a closed cabin and have no contact with passengers.
The sick driver's colleagues will be tested.
The MIVB's An Van Hamme: "We've drawn up a list of people who were in contact with the driver. So far, of the people who were tested as a precaution, only one tested positive. This employee is being examined in hospital and X-rays will be taken.