Is Legionnaires’ Disease?
Legionnaires’ disease is
a severe type of pneumonia, or lung infection. Bacteria called Legionella cause this infection. The
bacteria were discovered after an outbreak at a Philadelphia convention of the
American Legion in 1976. Those who were affected developed a form of pneumonia that eventually
became known as Legionnaires’ disease.
Legionella bacteria usually thrive in warm water. People
become infected with Legionella by breathing in contaminated
droplets of water in the air. Outbreaks have been linked to water systems in
hospital buildings and to whirlpool spas in hotels and cruise ships.
Approximately 8,000 to 18,000 people
are hospitalized in the United States each year for Legionnaires’ disease. However,
the number of infections is probably higher because many infections aren’t
diagnosed or reported. Some cases are so mild that affected individuals never seek
treatment. The symptoms of Legionnaires’ disease are similar to those of other
types pneumonia. These symptoms may include fever, chills, and a cough.
Many people who are exposed to Legionella don’t become
sick. When illness does occur, however, it’s important to see a doctor right
away. Legionnaires’ disease is a serious, life-threatening illness that
requires prompt treatment.
Legionella may also cause a more mild condition
referred to as Pontiac fever.
Pontiac fever doesn’t cause pneumonia and isn’t life-threatening. It has
symptoms similar to those of a mild flu, and it usually goes away on its own.
Pontiac fever and Legionnaire’s disease are sometimes collectively called Legionellosis.
Are the Symptoms of Legionnaires’ Disease?
Legionnaires’ disease will usually start causing symptoms within two
to 14 days after exposure to the bacteria. This period is called the incubation
period. The symptoms are similar to those of other types of lung infections.
The most common symptoms include:
- a fever above 104°F
- a cough, with or without mucus or blood
Other symptoms may include:
- muscle aches
- a loss of appetite
- chest pain
Causes Legionnaires’ Disease?
Bacteria called Legionella
cause Legionnaires’ disease. The bacteria invade the lungs and cause an
infection known as pneumonia.
Legionella usually live in warm freshwater. Common
- hot tubs
- whirlpool spas
- swimming pools
- cooling systems or air-conditioning units for
large buildings, such as hospitals
- public showers
- natural bodies of water, such as lakes, rivers, and
The bacteria can survive outdoors, but they’re known to multiply
rapidly in indoor water systems. People get infected by inhaling water droplets
or mist in the air that’s contaminated with the bacteria. The disease can’t be
spread directly from person-to-person.
Is at Risk for Legionnaires’ Disease?
Not everyone who breathes in contaminated air droplets will get
sick. However, you’re at a higher risk for developing Legionnaires’ disease if
- are over age 65
- have a weakened immune system due to another
- have a chronic lung disease
- have a job that involves maintaining cooling or
air conditioning systems
- abuse alcohol
- smoke cigarettes
Are the Complications of Legionnaires’ Disease?
When Legionnaires’ disease goes untreated, life-threatening complications
can develop. These include:
- respiratory failure, which occurs when fluid
builds up in the lungs
- kidney failure, which develops when the kidneys
aren’t working correctly
- septic shock, which is a serious infection that
leads to organ failure and very low blood pressure
These complications can progress rapidly, especially in people
who already have weakened immune systems.
Is Legionnaires’ Disease Diagnosed?
Your doctor can diagnose Legionnaires’ disease by testing your blood
or urine for the presence of Legionella antigens. Antigens are substances that your
body recognizes as harmful. Your body produces an immune response to antigens
to fight infection. Your doctor may also test a sample of sputum, or phlegm, for
the Legionella bacteria.
Your doctor might also perform a chest X-ray. While the X-ray
can’t be used to confirm Legionnaires’ disease, it can help determine the severity
of your lung infection.
Is Legionnaires’ Disease Treated?
Legionnaires’ disease is always treated with antibiotics.
Treatment is usually started as soon as the disease is suspected, without
waiting for confirmation. Prompt treatment significantly lowers the risk of
Many people completely recover with treatment, but most will need
care in the hospital. Elderly people and those with other health conditions are
particularly vulnerable to the effects of Legionnaires’ disease. While in the
hospital, they may receive oxygen or other breathing support. They may also be
given fluids and electrolytes through a vein in their arm (IV) to prevent
Is the Outlook After Treatment?
The outlook is typically good for healthy people who receive
prompt treatment. However, the length of recovery time will depend on the
severity of the disease and how quickly treatment is received. Faster treatment
means better results.
Legionnaires’ disease is usually more serious in elderly people
who have weakened immune systems or other medical conditions. If you’re
elderly, you have a higher risk of developing complications and you may need to
stay in the hospital for an extended period.
Can Legionnaires’ Disease Be Prevented?
There’s no vaccine available for Legionnaires’. However, it’s
possible to prevent the disease by properly disinfecting and cleaning potential
sources of the Legionella bacteria. Preventive measures include:
- disinfecting and cleaning cooling towers
- regularly draining and cleaning pools and hot
- using chemical treatments, such as chlorine, in
pools and spas
- keeping hot water systems above 140°F and cold
water systems below 68°F
Avoiding smoking can also significantly lower your risk of
infection. Smokers are much more likely to develop Legionnaires' disease if they’re
exposed to Legionella bacteria.