One person on the Upper East Side died of Legionnaires’ disease and six others were sickened by the bacteria-borne illness, officials said Friday.

The Health Department said the person who died was over 90 years old and had “significant underlying health conditions.”

Four people were recovering in hospitals and two others were discharged.

“There are no common sources of exposure among these patients other than living in the same area of the city,” said Demetre Daskalakis, the Health Department’s deputy commissioner for disease control, in an alert to health providers.

All the cases were diagnosed between May 22 and June 8 in Lenox Hill, which covers 60th to 77th Streets between Lexington and Fifth avenues.

Investigators are focusing on water towers as they seek to determine the source of the cluster.

Officials say there are 200 to 400 cases of Legionnaires’ disease in the city every year.

The fatality rate is estimated at 9 percent.