NEW YORK — The death toll from an outbreak of Legionnaires’ disease has risen from four to seven people, city health officials announced Monday at a public town hall meeting.

“We are taking this very seriously,” Dr. Mary Bassett, the city’s health commissioner, told the audience at the Bronx Museum of the Arts.

More than 80 people have been diagnosed with the disease, which is caused when water contaminated with a certain bacteria is inhaled into the lungs. Of those sickened, 64 have been hospitalized, with 28 of them treated and discharged.

The seven people who died were all older and had other health problems, officials said.

Dr. Jay Varma, deputy commissioner for disease control for the city Department of Health, emphasized that the disease was not passed on from person to person and that most people weren’t at risk. “This is still a pretty rare disease,” he said.

There have been 2,400 cases nationwide this year. The legionella bacteria were discovered last week at a Bronx hotel and in equipment at a hospital.

Officials have traced the likely cause of the outbreak to cooling towers, which can release mist. They said 17 towers in the area have been tested, with five testing positive for legionella bacteria. They said at the meeting Monday that all five of the towers have been decontaminated.

In a statement, Mayor Bill de Blasio said new legislation requiring inspections, sanctions and other regulations for property owners whose buildings test positive for the disease would be considered this week.

“Legionnaires’ disease outbreaks have become far too common over the past 10 years, and the city will respond not by only addressing an outbreak as it occurs but with a new plan to help prevent these outbreaks from happening in the first place,” he said.

The disease is easily diagnosed and treated with antibiotics. It poses the most risk to people who have underlying medical conditions, health officials said.