Yes, but risk is low
Legionnaires' disease is an infection with a legionella bacteria
that causes a pneumonia
It is transmitted in a waterborne fashion, often from cooling towers, humidifiers and such. It is not spread person-to-person. It is treated with antibiotics if found. Avoiding the source is the best way to avoid infection, and yes, you could get it from a water source at your spa, but it is uncommon.