The hunt was on.

An outbreak of Legionnaires’ disease had erupted in Harlem, killing six people and sickening more than 100 others. Officials said the bacteria that cause the illness had been spread through the air starting in late July by mist from infected water towers atop buildings in the neighborhood.

While doctors treated infected patients, public health researchers were in a race to pinpoint which towers were harboring the pathogen.

By late August, bacteria had been found in 12 towers, and the search had moved from the rooftops of Harlem to a hulking building farther south in Manhattan, where scientists needed to match bacterial samples from patients with those taken from water tanks.

That has moved the hunt into a stage that health officials say hinges on the slow growth of bacterial cultures and the exacting process of genomic sequencing, all of which can take weeks to get right.

“We watch science shows or ‘Law & Order,’ and the same day a murder happens, Mariska Hargitay is in the medical examiner’s office and is like ‘OK, what’s the verdict?’ and they already know everything,” Chantal Gomez, a spokeswoman for the New York City health department, said. “But that’s not reality. The reality is public health takes time.”

The juxtaposition between the anxious wait for answers and the slow process of growing and analyzing bacterial samples has been a defining feature of this stage of the outbreak, which was detected through routine public health surveillance.