NEW YORK (CBSNewYork) — New Yorkers were on edge Sunday as the number of people sickened with Legionnaire’s disease continued to grow.

The city’s Department of Health confirmed the number of cases increased overnight to 16 people, all of whom are part of a community cluster localized in parts of Hamilton Heights and Washington Heights.

Health officials believe vapor from water cooling towers is spreading bacteria that causes the disease. Legionnaire’s is a pneumonia that causes flu-like symptoms that appear two to ten days after exposure.

“It almost killed me,” Washington Heights resident Lorenzo McGougan told CBS2. “Believe me, I was near there. I’ve never been that sick in my life.”

The 60-year-old McGougan says he reported his case of Legionnaire’s to the DOH in May. At a community meeting last week he pressed officials why his building’s water cooling tower was never inspected.

Health officials say McGougan’s case isn’t one of the 16 included in the most recent cluster. There are between 200 and 500 cases of Legionnaire’s every year, but officials say they become more concerned when they’re clustered. The the source of the current rash of cases a mystery, the DOH is handing flyers to educate members of the community.

“We rely on the people of this community to look after themselves, look after their neighbors, and seek care early,” DOH Commissioner Dr. Mary Bassett said.

The infected patients are between 40 and 80 years old. At 50, officials say there’s a higher risk of contracting the disease which can be easily treatable with antibiotics.

The city began regular and mandatory inspections of cooling systems after 12 people died from a Legionnaire’s outbreak in the Bronx three-years-ago. So far, officials have tested at least 20 cooling towers in Upper Manhattan in an attempt to isolate the source of the cluster.