In late July, two citizens of New York died and more than 40 people were infected with a particularly scary form of pneumonia known as Legionnaires’ disease. Now, on the morning of August 4, a total of seven people have died and there are now 81 confirmed cases of the disease.

Also known as Pontiac Fever, Legionnaires’ disease is the stuff of science fiction: Think of M Night Shyamalan’s deadly flora in “The Happening,” the experimental “rage” virus in “28 Days Later” or the alien pods from “Invasion of the Body Snatchers.”

Legionnaires’ disease is a potentially deadly pneumonia infection spread by a benign source: bacteria-infected water mist from plumbing, cooling towers, air conditioners, hot tubs and showers.

The disease is caused by bacteria in the Legionellaceae family, which consists of more than 42 species, constituting of 64 serogroups. The primary cause of Legionnaires’ disease is Legionella pneumophila, which was identified in the summer of 1976, when an outbreak occurred in and around the 58th annual convention of the American Legion at the Bellevue-Stratford Hotel in Philadelphia.

Of the 182 people infected, 29 died, and it was that incident that inspired the name of a disease that has caused a great deal of illness and death in the decades since.

Researchers have discovered what they believe to be cases of Legionnaires’ disease going back to World War II, and retroactive research has found the bacteria may have been responsible for mass illness and deaths in Philadelphia, Washington, D.C. and Minnesota.

After the disease was named in 1976, consider these frightening outbreaks of pneumonia attributed to the Legionellaceae bacteria:

  • In April of 1985, 175 patients were admitted to the District or Kingsmead Stafford Hospitals with chest infection or pneumonia. Twenty-eight people died. The infection was traced to an air-conditioning cooling tower on the roof of the hospital where patients went for treatment.
  • During the Westfriese Flora flower exhibition in Bovenkarspel, Netherlands, in March of 1999, 318 people were stricken with Legionnaires’ disease, with 32 deaths and possibly more as some people were buried before LD had been diagnosed.
  • Between July 7 and 22 of 2001, more than 800 cases of LD were treated at a hospital in Murcia, Spain. There were six deaths.
  • In September of 2005, 127 residents of a nursing home in Canada were stricken with pneumonia, resulting in 21 deaths. Again, the source was found to be air conditioning cooling towers on the roof of the nursing home.
  • In November of 2014, more than 300 people in a region north of Lisbon, Portugal, were treated for what was found to be LD. There were seven deaths and the source was found to be cooling towers at a fertilizer plant.
  • In this latest July 2015 outbreak in the Bronx, the source was found to be an apartment building at the Lincoln Hospital complex where many patients were treated.

Here is basic information about Legionnaires’ disease.

What is it? Also known as legionellosis or Legion fever, Legionnaires’ disease is a form of pneumonia caused by any species of bacteria belonging to the genus Legionella. There are more than 42 species of bacteria in the Legionellaceae family, but 90 percent of cases of LD are caused by Legionella pneumophila. Symptoms are similar to pneumonia, and include cough, shortness of breath, high fever, muscle aches and headaches, which can begin two days to two weeks after exposure to the bacteria.

In more severe cases, patients suffer from diarrhea, vomiting, loss of coordination and cognition, impairment of kidneys and liver and lung failure.

Symptoms are similar to pneumonia, and include cough, shortness of breath, high fever, muscle aches and headaches, which can begin two days to two weeks after exposure to the bacteria.

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According to the Centers for Disease Control, “Legionella can be found in natural, freshwater environments, but they are present in insufficient numbers to cause disease. Potable (drinking) water systems, whirlpool spas, and cooling towers provide the three conditions needed for Legionella transmission-heat, stasis, and aerosolization; therefore, these are common sources of outbreaks.”

How common is it? “Each year, between 8,000 and 18,000 people are hospitalized with Legionnaires’ disease in the U.S.,” says the CDC. “However, many infections are not diagnosed or reported, so this number may be higher. More illness is usually found in the summer and early fall, but it can happen any time of year.”

What is the survival rate? The majority of those infected survive. The fatality rate can be anywhere from 5-30 percent of those infected, says the CDC. (For Pontiac fever, the fatality rate is zero.)

The CDC also says that “most healthy individuals do not become infected with Legionella bacteria after exposure.” At-risk people include those 50 years old and up, current or former smokers, people with chronic lung diseases like COPD or emphysema, people with weak immune systems from cancer, diabetes or kidney failure, and people taking drugs that weaken the immune system such as chemotherapy patients.

What is the current treatment? LD “requires treatment with antibiotics (drugs that kill bacteria in the body), and most cases … can be treated successfully with antibiotics,” says the CDC. “Healthy people usually get better after being sick with Legionnaires’ disease, but hospitalization is often required. Pontiac fever goes away without specific treatment. Antibiotics provide no benefit for a patient with Pontiac fever.”

Who else has died of it? In November of 2014, a popular British TV chef named Ross Burden was admitted to an Auckland, New Zealand, hospital with leukemia, but it was reported that he died of LD contracted from an infected water supply at the hospital. He was 45 years old.

Update: Ten now dead from outbreak.