Chances are you’ve heard about Legionnaires’ Disease at some point over the last month. What is it, how do you get it, and why does it cause grown men to act like warring middle school girls? Here’s what you need to know.

What Is Legionnaires’ Disease?

Legionnaires’ disease is not, as I initially guessed from the fancy name, an old time-y soldier’s affliction. It is, however, a serious and sometimes fatal airborne form of pneumonia caused by a bacterium known as Legionella which typically presents in warm water.

First, a bit of history via the New York Times—the respiratory disease was so-named because it broke out in 1976 at an American Legion convention in Philadelphia, ultimately killing 34. It strikes anywhere there’s water—including “in apartment complexes, office buildings and even on a cruise ship.” And this outbreak has been one of the deadliest so far.

So how does it strike?

According to Forbes, the bacteria is often present in natural fresh water sources at levels low enough to pose little to no health threats. The bacteria gets dangerous, however, when it’s introduced to man-made water systems like cooling towers, hot tubs, shower heads—even decorative fountains have harbored the strain. It can be found pretty much anywhere with warm water, where the bacteria will often “multiply to high concentrations” that can be fatal to humans.

People become sickened after inhaling contaminated aerosol droplets generated from these sources. Unlike most other pneumonias caused by microorganisms, this disease is not transmitted person-to-person; it is purely of environmental origin.

Don’t breathe a sigh of relief—and definitely don’t breathe in—just yet: even though its not an infectious disease, the Times reports catching it can be as easy as walking by contaminated “air-conditioning systems, exposed overhead pipes and other common features of urban life.”

Ok, maybe breathe—the CDC says many people exposed to the bacteria don’t get sick, and those who do usually have some sort of pre-existing condition. So how do you know if you’ve caught it? According to legionella.org, symptoms of infection can often include “a high fever, chills, cough, muscle aches, headaches, and diarrhea.”

Where Are People Getting Sick?

The most recent outbreak you’ve been hearing about has primarily affected residents of the South Bronx. Officials haven’t yet pinpointed the exact location where the outbreak began, but they believe it originated in one of five spots where the largest clusters of infections have been identified.

The most likely culprit for Legionnaires’ ground zero? The Opera House Hotel, a lively boutique hotel built in an old theater space where Harry Houdini and the Marx Brothers once performed. But, the New York Times reports, the outbreak might also be tied to either 1) a medical building, 2) a mall, 3) a Verizon building or 4) a plastic fabrication company:

The other buildings in the group of towers with initial positive tests were Lincoln Medical and Mental Health Center, Concourse Plaza shopping mall, a Verizon office building and Streamline Plastics Company.

Authorities say the bacteria was found in the cooling towers at all five of those locations in recent weeks.

What the F is a Cooling Tower?

Maybe you already knew what a cooling tower is. Why is she explaining this, you wonder, perhaps slamming your computer shut with disgust. You, my friend, who is no longer reading this, are smarter than I, and though you’ll never know it, I commend you.

For the rest of us dummies, cooling towers are heat rejection devices that provide evaporative cooling for sexy purposes like HVAC systems and chemical plants. According to OSHA, the water vapors produced through this process are often in “the ideal temperature range for Legionnaires’ disease bacteria (LDB) growth, 20°-50°C (68°-122°F).” Mmmm toasty.

Cleaning the towers regularly can help stem outbreaks—but only sometimes. At least one of the sites to test positive followed CDC cleaning guidelines and yet it still managed to play warm host to the bacteria, the Times reports:

Even cooling towers that are cleaned can harbor the Legionella bacteria. The one at Lincoln Medical and Mental Health Center is cleaned and disinfected every six months, according to recommended guidelines, hospital officials said. Before its most recent cleaning on July 29, after testing positive for Legionella bacteria, the tower had been cleaned in March.

But, it may surprise you to learn, getting rid of the bacteria can take less effort than kicking out your roommate’s weirdo boyfriend—according to the New York Times, decontamination is as easy as “flushing contaminated cooling towers with bleach and then fresh water.”

Where Has It Been Found and What’s the Death Toll So Far?

So far, at least 11 cooling towers within the South Bronx outbreak zone and 7 outside of it—so 18 sites in all—have tested positive for the bacteria.

According to the most recent data, 12 people have died so far, 76 hospitalized and released, and 113 sickened overall. According to the CDC, the disease is typically fatal to between 5 and 30 percent of patients; infection is often exacerbated by pre-existing conditions like smoking and old age—city officials say all 12 of the dead had health problems prior to infection.

Why Aren’t Rich People Getting Sick?

It seems affluenza is a great immunization against Legionnaires’ Disease—it’s no coincidence that this outbreak is centered in a largely impoverished area. The reason, experts say, is two-fold: 1) poor people tend to have bad health (the South Bronx is reportedly one of the unhealthiest counties in the state) and 2) buildings in poor areas are less likely to keep water systems clean (the South Bronx also holds the dubious honor of being one of the poorest counties in the state). Via the New York Times:

The study also noted that the disease was often concentrated in impoverished neighborhoods, saying, “If environmental issues in high-poverty neighborhoods contribute to the disparity, greater effort may be warranted, for example, on the upkeep of cooling towers and water systems in the buildings in these areas.”

Which is why, according to the Times, the “nationwide surge” of the disease has disproportionately affected impoverished neighborhoods.

Why Are New York Politicians Giving Different Statistics?

This week New York governor Andrew Cuomo and New York mayor Bill de Blasio each held a press conference—at the same damn time—where they announced new statistics about the outbreak.

Two separate press conferences about the same thing? What’s that all about? Well. Let me just tell you these two men did not join politics to make friends. It’s honestly a wonder de Blasio can still walk, he’s been kneecapped by Cuomo so many times. Take, for example, the CDC: after de Blasio declined to call in the a team last week, saying he felt it was unnecessary, Cuomo immediately had a team dispatched.

So it’s not a big surprise they decided to handle the press separately. What was surprising, however, was that their numbers didn’t match up.

At issue? How many additional towers have tested positive for the bacteria since the city and the state both began widespread testing throughout the South Bronx and other parts of the city (according to the New York Post, city officials tested at least 39 cooling towers over the weekend, with more tests to come.)

So on Monday, de Blasio told reporters gathered at City Hall his interpretation of the weekend’s findings: two new sites had tested positive for the bacteria. And at the same time, somewhere in Midtown, Cuomo told reporters de Blasio was wrong: three new sites had tested positive.

So uh... what’s going on here, fellas? The official story is it was just a miscommunication. The actual story is that I assume Andrew Cuomo would probably kill Bill de Blasio if he could get away with it. Via the Post:

City officials said 39 cooling towers in the South Bronx outbreak area have been tested by the city, with two new sites coming back positive – raising the total to 12.

As those numbers were coming out, Cuomo separately told reporters that state inspectors had found 3 new sites that tested positive outside of the impact zone.

A Cuomo spokeswoman said later that Dr. Howard Zucker, the state health commissioner, had called Bassett to brief her on the discovery and left a message because Bassett was already at de Blasio’s news conference.

Cuomo was then briefed on the findings, which led to him telling the media before the mayor did.

Afterwards, Cuomo reportedly “smiled” when a reporter asked if he would back a challenger to de Blasio in the next election.

Is This Uncontrollable Passive Aggression a Side Effect of Legionnaires?

Nah. They’re just idiots.

Contact the author at gabrielle@gawker.com.