New York City Mayor Bill de Blasio has signed legislation aimed at preventing further outbreaks of deadly Legionnaires' disease.

An outbreak that began last month killed 12 people in the Bronx and hospitalized more than 100 others.

The requires the regular inspection and cleaning of cooling towers.

The towers emanate warm mist that can spread the . They are believed to be the source of the outbreak, the largest in the city's history.

The legislation was a joint effort between the mayor's office, Gov. Andrew Cuomo's office and the New York City Council.

Building owners have 30 days to register their towers.

Those who do not register or who fail to clean their towers are subject to fines and misdemeanor charges.