Most New Yorkers don’t think about how their buildings’ air conditioning systems work. Maybe they should, health officials and lawyers tracking a spike of new Legionnaires’ disease outbreaks and related lawsuits tell Bloomberg Law.

Rising temperatures, more virulent strains of the potentially lethal disease, and aging populations and cooling and plumbing systems, are just some of the many reasons driving the boom in New York and other U.S. cities.

Reported Outbreaks Steadily Rising

The number of Legionnaires’ cases reported to...