The death toll in New York's outbreak of Legionnaires' disease has risen to eight, out of a total of 97 cases of infection, city authorities said Wednesday.

The eight victims were all "older adults", who had other medical problems as well as Legionnaires', the authorities said.

The total number of infections was up by 11 from the previous day's tally. But the most severe Legionnaire's outbreak recorded in New York has passed its peak, mayor Bill de Blasio has said.

Of the 92 people hospitalized in the , 48 have been treated and returned home.

A form of pneumonia, Legionnaires' disease is spread by a bacteria that has recently been discovered in the cooling towers of five buildings in the South Bronx neighbourhood.

The infections were likely spread through ventilation systems connected to the towers, which have since been decontaminated.

Legionnaires' cannot be passed from one person to another and can be treated with antibiotics.

The bacteria that cause the disease thrive in warm water, such as that found in hot water pipes and air-conditioning systems.