Legionnaires' disease is a potentially fatal lung infection. It is a form of pneumonia that can happen when a person breathes in the Legionella bacteria. Most cases are due to poor water management.
Around 5,000 people are diagnosed with Legionnaire's disease in the United States every year, and in one in 10 cases, it is fatal. The incidence of Legionnaire's disease increased nearly fourfold from 2000 to 2014.
Contents of this article:
- History of Legionnaires' disease
- How do people catch Legionnaires' disease?
- Signs and symptoms of Legionnaires' disease
- Causes and risk factors of Legionnaires' disease
- How is Legionnaires' disease diagnosed?
- Treatment for Legionnaires' disease
- Complications of Legionnaires' disease
- Preventing Legionnaires' disease
History of Legionnaires' disease
Legionnaires' disease takes its name from the first recognized outbreak, which occurred during a convention of the American Legion in Philadelphia, in July 1976.
Poor water management can result in Legionnaires' disease.
The bacteria spread through the air conditioning system.
The first person died on 27 July, 3 days after the convention ended. During the following week, over 130 people, mostly male, were admitted to hospital, and 25 of them died.
They had all been to the same conference, and they had all stayed at the same hotel.
In January 1977, the cause was identified as a previously unknown bacterium, which was then named Legionella, and Legionnaires' disease is also known as legionellosis.
How does legionnaires' disease occur?
Legionnaire's disease mostly appears as single isolated cases, not linked to any recognized outbreak. If outbreaks do occur, they are more likely in the summer or early autumn, but they can happen at any time of year.
Legionella bacteria commonly exist in water. They are found in rivers and lakes, and some other water sources, generally in low numbers.
Occasionally, they may get into artificial water supply systems, for example, through the evaporative condensers that are associated with air conditioning and industrial cooling. Legionella bacteria can appear wherever water is being artificially supplied or used.
People catch Legionnaires' disease by inhaling small droplets of tainted water, but not from drinking it. An infected person cannot generally pass the infection to another person, although it is possible in rare cases.
Legionnaires' disease is more likely in places with complex water supply systems, such as hospitals, hotels, and buildings that cater for large numbers of people.
The bacteria only survive within a certain temperature range. Keeping water below 20 degrees Celsius, or 68 degrees Fahrenheit, or above 60 degrees Celsius or 140 degrees Fahrenheit, can prevent Legionnaires ' disease.
Signs and symptoms of Legionnaires' disease
Legionnaires' disease may be hard to diagnose at first because its signs and symptoms may be very similar to other forms of pneumonia.
Signs and symptoms usually appear between 2 and 10 days after initial infection.
They typically include:
- High fever, possibly over 40 degrees Celsius or 104 degrees Fahrenheit
- Muscle aches
Some patients may experience only muscle aches and a mild headache to start with, and the other signs start to appear 1 to 2 days later.
When more severe symptoms appear, the fever will be high. The muscle pains often get worse, and the patient starts to have chills.
Often, the bacteria enter the patient's lungs, leading to a persistent cough, shortness of breath and chest pains. The cough may be dry at first, but as the infection progresses, there will be mucus and maybe blood.
Around 1 in 3 infected patients will experience nausea, vomiting, and diarrhea. Those with gastrointestinal symptoms will usually have an extremely reduced appetite.
There may be confusion and altered mental status.
Causes and risk factors of Legionnaires' disease
The Legionella bacteria exist in rivers, lakes and other places with fresh water, but numbers are usually low because the water temperature in such places is too low for the bacteria to multiply rapidly.
Legionnaire's disease resembles pneumonia, and it can be fatal.
In artificial water systems, however, water temperatures may be higher. Temperatures between 20 degrees and 45 degrees Celsius, or from 68 degrees to 113 degrees Fahrenheit, can be ideal for the bacteria to multiply rapidly and spread. This can infect major parts of the water system.
An ideal environment for the bacteria to reproduce and spread rapidly has not only the right temperature, but it also provides the right food. Impurities, such as algae, sludge, rust, and lime scale are types of food for this sort of bacteria.
Hotels, hospitals, and large buildings can provide the ideal environment, if they have an air-conditioning system that uses water for cooling.
Other types of artificial water systems that can potentially become contaminated include fountains, baths, showers, water taps, gardening sprinklers, spas, and humidifiers.
People at the highest risk of developing Legionnaires' disease tend to be over 50 years of age.
Those with respiratory problems, including smokers, patients with chronic obstructive pulmonary disease (COPD) and those with lung cancer, are more susceptible.
Heavy alcohol consumption increases the chance of having the disease, and one study has suggested that using cannabis may increase susceptibility.
How is Legionnaires' disease diagnosed?
Physicians will look at the patient's signs and symptoms, and ask whether they have recently spent time in a large building such as a hotel or hospital.
Other tests that can help to detect the disease include:
- Urine test to detect antigens, the special proteins produced by the immune system to fight the Legionella bacteria
- Blood tests
- Imaging scans to check the state of the kidneys and lungs
- A lumbar puncture, or spinal tap, can reveal whether the disease has affected the brain.
Treatment for Legionnaires' disease
Treatment typically involves antibiotics, given by mouth or intravenously. A course of antibiotics normally lasts between 10 and 14 days. Adverse effects may include nausea, dizziness, headaches, loss of appetite, and chest pains.
Some patients may receive intravenous fluids to prevent dehydration.
Older patients and those with a weak immune system or another chronic condition, such as diabetes, may be hospitalized.
If the lungs are badly affected, the patient will be given oxygen.
Complications of Legionnaires' disease
Respiratory failure can occur, in which the body does not get enough oxygen from the lungs to function properly.
Kidney failure is possible, due to an accumulation of fluids and waste in the blood.
Septic shock can occur if the infection reaches the blood. A sudden drop in blood pressure means that insufficient blood will reach the vital organs, including the brain and the kidneys.
Preventing Legionnaires' disease
Water systems must be properly maintained to prevent Legionnaires' disease.
The water must be kept below 20 degrees Celsius or 68 degrees Fahrenheit, or above 60 degrees Celsius or 140 degrees Fahrenheit. Impurities should not be allowed to build up in the water.
Owners and managers are urged to follow guidelines regarding water safety in commercial buildings. The Centers for Disease Control and Prevention (CDC) state that most cases that occur could be prevented through better water management.