Greek public health announcement regarding outbreaks ~2018: https://www.acg.edu/about-acg/institute-of-public-health/fac...

An anecdotal account of a man contracting Legionnaire's while on holiday in Greek apartment: https://www.irwinmitchell.com/news-and-insights/newsandmedia...

An older account of a similar ocurrance in a hotel, just as you describe: https://www.sciencedirect.com/science/article/abs/pii/004313...

Granted, no mention of this particular cultural artifact. Global temperature warming was cited in some reports as part of the cause of these outbreaks. It seems that the bacteria really likes to live in showerheads, so especially older shower heads can accumulate legionella especially given commonly lukewarm temperatures. This creates a perfect storm of ideal reservoirs, protected, moist, temperature conditions and aerosolized distribution.

Nasty.