Can the risk of legionnaires' disease be determined by geographical location?

Possibly: Historicaly legionella was 1st diagnosed in philladeplhia on a convention of legioners - mostly older people and some of them had been usisng habitually excess of alkohol and smoked.It was a susceptible population. But it was found also in california and elswhere in airconditioning system where moist harbors bacteria and it gets into an air circullation.

No: The bug that causes "legionaire's disease" can be found in all climates. It is not spread from person to person. It has a predilection to occur more in the summer months, and its not entirely clear why. Some speculate that it can inhabit air conditioning towers, but it has also been found in the environment (soil). It is more likely to affect those with underlying lung or heart disease.