What is Legionnaires’ disease?
Legionnaires’ disease is an atypical pneumonia caused by a particular species of bacterium, aptly named for it’s source and origin. It acquired its name in July 1976, when an outbreak of pneumonia occurred among people attending an American Legion convention at the Bellevue-Stratford Hotel in Philadelphia, Pennsylvania. There were 182 reported cases consisting of mostly men, among which 29 died. Six months after the initial cases were identified, physicians discovered that the illness was caused by this particular bacterium, which they named Legionella pneumophila.
This bacterium is typically found in freshwater and can contaminate hot water tanks, tubs, and cooling towers. It is an invisible, odorless bacteria that spreads to humans upon breathing in mist that contains it. Risk factors for the disease include older age, history of smoking, chronic lung disease, and poor immune function.
There are more than 50 known species of Legionella, but one strain, Legionella pneumophila serogroup 1 (which accounts for 70 percent of the diseases caused by this bacteria) is the most common. According to the United States Centers for Disease Control and Prevention, approximately four percent of individuals who are exposed to aerosolized, bacteria-laden water droplets will contract Legionnaires’ disease. The disease affects approximately 20,000 people in the United States each year. The fatality rate has ranged from 5% to 30% during various outbreaks.
How is the disease diagnosed?
Legionnaires’ disease can be diagnosed by laboratory testing of the patient’s urine, blood, respiratory secretions, lung tissue, pleural fluid, or other sterile fluid. The most common test is a urinary antigen test which is a simple, quick, and reliable test to detect Legionella pneumophila serogroup 1.
Diagnostic tests typically show reduced kidney and liver functions, and that electrolyte levels are abnormal. The chest X-rays also show the pneumonia with consolidation in the bottom portion of the lungs. In the lungs, the bacteria are consumed by macrophages, a type of white blood cell, inside of which the Legionella bacteria multiple and kill the macrophage.
What are the symptoms?
Patients with Legionnaires’ disease often report fever, chills, and a cough, which may be dry or may produce sputum. Nearly everyone with the disease experiences a fever and one-third cough up blood. Patients also have muscle aches, headache, fatigue, loss of appetite, chest pain, diarrhea and vomiting.
Respiratory failure, septic shock, and acute kidney failure are all complications associated with the disease. Early treatment with antibiotics is the best line of defense against complications.
How do we prevent the disease?
The most effective way to prevent the disease is to eliminate the potential exposure. Water systems such as cooling towers, spas, and pools must be properly maintained and up to current health and safety codes. You can purchase pool test strips to verify that your water is properly maintained: use the test strips to check for adequate free chlorine (2-4 parts per million), bromine (4-6 parts per million) and pH levels (7.2-7.8 on the 1-14 scale).
Where have the outbreaks occurred?
The following locations are examples of the some of the biggest and most recent outbreaks of Legionnaires’ disease:
(i) In late September 2005, 127 residents of a nursing home in Canada were infected with 21 death resulting from the outbreak. The source of the bacteria was traced to the air conditioning cooling towers on the nursing home’s roof;
(ii) In November 2014, 302 people were hospitalized following an outbreak of Legionella in Portugal and 7 related deaths were reported. The source of the contamination was located in the cooling towers of a fertilizer plant;
(iii) In July and August 2015, 120 people were sick and 12 died from a contaminated cooling tower located on top of a hotel in the Bronx, New York; and
(iv) Between June 2015 and January 2016, 87 cases of Legionnaires’ disease were reported within the city of Flint, Michigan and the surrounding area. 10 of the cases were fatal.