Story highlights All of the victims had additional underlying medical problems

There have been 81 reported cases; 64 people have been hospitalized

New York (CNN) The number of deaths in the New York City Legionnaires' disease outbreak is up to seven.

All of the victims were older adults with additional underlying medical problems, according to the office of Mayor Bill de Blasio.

The office said Monday that there have been 81 reported cases of the flu-like disease. Sixty-four people have been hospitalized.

Legionnaires' disease is a respiratory bacterial infection usually spread through mist that comes from a water source, such as cooling towers, air conditioning or showers. It is not transmitted person to person. Symptoms of the disease include fever, chills and a cough.

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