Yesterday evening, about a week after the city's Health Department declared the largest Legionnaires' outbreak in NYC history—which killed 12 New Yorkers and sickened more than 120 others—officially over, an all-girls school on the Upper East Side confirmed that it had tested positive for low levels of Legionnaires' bacteria in one of its cooling towers.

The cooling tower atop Convent of the Sacred Heart school at 1 East 91st Street—alma mater of Lady Gaga and sister heiresses Paris and Nicky Hilton—is located inside a Florentine plazzo on New York's "grandest block." Two rounds of disinfection have already been conducted, and health officials say that the chance of infection within the school, which casts a shadow on Central Park, is very low.

In a letter to staff sent on Friday, and later published by CBS, Principal Joseph Ciancaglini wrote:

“While it was only found in small amounts and is unlikely to have infected anyone, we have closed the mansions this weekend to eradicate the bacteria. The cooling system will be disinfected twice over the weekend, supervised by an environmental engineering firm that is skilled in dealing with this bacteria."

"The Convent of the Sacred Heart School properly disinfected its cooling tower," said the Health Department in a statement. "Its cooling tower's positive test result, and subsequent disinfection, underscores the importance of the new legislation the Mayor signed just two weeks ago."

Convent of the Sacred Heart was tested as a result of emergency legislation passed in mid-August. Voted in unanimously by the City Council, it requires that every single cooling tower in the city be systematically tested for Legionnaires' bacteria.

The Health Department commented on the seemingly-anomalous nature of this positive test outside of the South Bronx (where the summertime outbreak was largely contained) pointing out that Legionella bacteria is in fact ubiquitous. Cooling towers happen to be ideal breading grounds for the bacteria, which can cause a diseases with pnemonia-like symptoms.

The school is reportedly open for faculty meetings today, and will begin classes next week as scheduled.