New York health officials are searching for the source of a Legionnaires' disease outbreak in the Bronx that has sickened 65 people and killed four since July 10.

Investigators have discovered the Legionella bacteria in air conditioning equipment at a hospital and a complex that houses a movie theater. Authorities do not know whether there is a link between the contaminated equipment and the outbreak, ABC7 Eyewitness News reports.

Thus far, two rooftop cooling systems have tested positive for the bacteria, one at Concourse Plaza on 161st Street, and the other an outside cooling tower at Lincoln Hospital. There is no clustering of cases in either of the identified locations, the city says. The cases have been centered in four neighborhoods in the South Bronx: High Bridge, Morrisania, Hunts Point and Mott Haven. The city has identified 20 cooling towers in the Bronx that need to be tested.

The total number of cases has risen steadily and now stands at 65, and Bronx residents are anxious and some feel the city has not responded quickly enough, according to the New York Times. These neighborhoods in the South Bronx have reported cases: Hunts Point, Longwood, Morrisania, Crotona Park, Claremont Village, Concourse Village, Woodstock, Highbridge, Concourse, and Mount Eden.

Most cases of Legionnaires' disease can be traced to plumbing systems with favorable conditions for growth of the bacteria, such as whirlpool spas, hot tubs, humidifiers, hot water tanks, cooling towers, and evaporative condensers of large air-conditioning systems.

The New York City Health Department is working to track down the source of the outbreak, and is interviewing those affected about their movements. At a news conference, Mayor Bill de Blasio said most New Yorkers are not at risk. Legionnaires' disease, which is caused by the bacteria Legionella, "can only come through the air that is dispersed out of the cooling towers, the mist that is dispersed out of them. So we know we have a localized problem," de Blasio said. The city's health commissioner, Mary Bassett, said, "No employees, no patients in the hospital have acquired Legionnaires' there." Bassett said they acquired the disease in the neighborhood" and we don't fully understand how," ABC7 reports.

Health officials advise New Yorkers with symptoms such as fever, cough, chills and muscle aches to seek medical attention. Additional symptoms include: headache, fatigue, loss of appetite, confusion, and diarrhea. Symptoms usually appear two to 10 days after significant exposure to Legionella bacteria. About 2,200 Legionnaires' illnesses have been reported nationwide since January 1, including more than 100 in New York City.

Groups at high risk for Legionnaires' disease include people middle-aged or older-especially cigarette smokers-people with chronic lung disease or weakened immune systems, and people who take medicines that weaken their immune systems (immunosuppressive drugs). Legionnaires' disease cannot be spread from person to person. Most people make a full recovery, but the Centers for Disease Control and Prevention (CDC) says that between 5 and 30 percent of those who get the disease die.

More information about Legionnaires' disease can be found on the Health Department web site: http://www.nyc.gov/html/doh/html/diseases/cdlegi.shtml.