Question A: This seems to be a type of pneumonia-causing infection. The fact that it has occurred to workers at all floors of a new building suggests a vehicle which can carry the organisms to all parts of the building. Water and air are therefore potential vehicles, but respiratory diseases are usually transmitted through the air. Legionella first came to notice in the air conditioning system of a modern hotel so it is a prime suspect.
Question B: The first step is to test for the bacterium Legionella pneumophila because pneumonia can be caused by many bacteria and fungi. If the test comes back positive the antibiotics of choice are azithromycin and clarithromycin. \beta-lactam antibiotics are not a good choice because Legionella pneumophila produces a beta-lactamase.
Question A: You are risking the lives of the newborn that still have not developed a mature immune reaction and you are risking the health of your co-workers who may be infected because of the contact with you.
Question B: You could be infected with RSV, which is small enough to pass through the material in the mask. RSV causes mild disease in adults but is serious in babies and young children.