Another person has died after contracting Legionnaires' disease, bringing the death toll in the Upper East Side outbreak to seven, according to city officials. Legionnaires' disease is a severe form of pneumonia caused by Legionella bacteria. Health officials have said they believe the outbreak was linked to contaminated cooling towers. It's the second Legionnaires' disease outbreak in Manhattan in the past two years. City officials have said they will release additional information about enforcement actions related to cooling tower compliance.