Legionaire's disease from water birth (city water used)

Two cases of legionaire's disease in infants who were born after mom had labor in water, aka water birth.

is it the water supply from the city, or because the water got stagnant in the pipes?

, it can be reduced by running hot water through the hose for 3 minutes before filling the tub to clear the hose and pipes of stagnant water and sediment.