Legionnaires disease is a serious form of pneumonia caused by the bacteria Legionella pneumophila, found in the contaminated water systems of hotels, hospitals, cruise ships and other buildings. It can cause severe, sometimes fatal illness if not diagnosed and treated early.
It affects the elderly, those with suppressed immune systems, smokers and people with chronic medical conditions such as lung disease, kidney disease or diabetes. Symptoms include fever, chills, cough with or without phlegm, muscle aches and headaches, and fatigue. Some patients may have other symptoms such as a loss of appetite or nausea and vomiting.
The bacterium thrives in warm, moist environments, and especially in hot or warm water or a place where there is a lot of humidity. These places include public swimming pools and hot tubs, hotel rooms and long-term care facilities.
Anyone can become infected with Legionella, but it is most common in older people, alcoholics, smokers and those with lung, kidney or diabetes problems. It is most commonly spread from person to person by breathing airborne water droplets containing legionella. These droplets are made when water is heated, cooled or humidified in a variety of ways, such as: cooling towers used for air conditioning, hot and cold water outlets, and wet air conditioning plants.
Those who get legionella often develop symptoms within two to ten days of exposure to the contaminated water system. The first signs are usually flu-like and include fever, chills, tiredness and headache. In about one-third of cases, a dry or wet cough develops that produces sputum.
A chest X-ray and laboratory tests are the main diagnostic methods used to identify legionella pneumonia. The X-ray may show pneumonia with consolidation (segregation) at the base of the lungs.
There is also a milder form of Legionella infection, known as Pontiac fever. This can be more difficult to diagnose because of the similarity in symptoms and flu like features.
The incubation period for both forms of legionellosis is about 1-2 days. The most serious form of the infection, Legionnaires’ disease, usually progresses rapidly and causes a high fever, shortness of breath and chest pain.
Many people with legionella disease recover, but a small number of patients develop complications including severe pneumonia, lung damage or death. These cases are most often hospitalized or admitted to an intensive care unit.
A sputum culture and urinary antigen testing are common test procedures for diagnosing legionella pneumonia. These test methods use media designed to enable the bacterium to grow at a higher rate than normal, so doctors can observe and identify it.
Other tests can help doctors find the source of the Legionella bacteria and to determine if the infection has affected the entire respiratory tract or just one lung. This information can help to prevent the infection in future.
