A growing cluster of Legionnaires' disease cases on Manhattan's Upper East Side has reached 23 confirmed infections, including 17 hospitalizations, according to city health officials. The New York City Health Department said the cases have been identified in the ZIP codes 10028, 10128 and 10075. No deaths have been reported. Officials said people who live, work or have visited those areas since late June should monitor for symptoms and seek medical care if they become ill.