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Symptoms and Signs of Legionnaires' Disease and Pontiac Fever (Legionellosis)

Doctor's Notes on Legionnaires' Disease and Pontiac Fever (Legionellosis)

Legionnaires' disease is a serious illness caused by Legionella bacteria that can result in fatal cases of pneumonia. Pontiac fever is a self-limited, flu-like illness, also caused by the Legionellabacteria. Legionellosis refers to the two illnesses caused by the bacteria of the genus Legionella (Legionnaires' disease and Pontiac fever).

Early symptoms of Legionnaires' disease include headache, muscle pains, fever, and chills. After a day or two, symptoms worsen and may include cough and shortness of breath (which worsens as the pneumonia progresses), gastrointestinal symptoms (nausea, vomiting, and diarrhea), confusion, chest pain, and body aches. In severe cases or if the disease is not treated Legionnaires' disease can progress to respiratory failure, renal failure, and death. Symptoms of Pontiac fever begin within two to three days of exposure and are much milder than in Legionnaires' disease and include fever, chills, and muscle aches. Symptoms usually resolve within a week with no long-term effects.

Medical Author: John P. Cunha, DO, FACOEP
Medically Reviewed on 3/11/2019

Legionnaires' Disease and Pontiac Fever (Legionellosis) Symptoms

The first symptoms of Legionnaires' disease are usually headache, muscle pains, fever, and chills. The symptoms worsen after one to two days and then may include

In severe forms or when left untreated, Legionnaires' disease can progress to respiratory failure, renal failure, and death. Patients hospitalized with Legionnaires' disease have a 10% mortality rate.

Pontiac fever symptoms start within two to three days of exposure and are much milder. The patient experiences fever, chills, and muscle aches. Pontiac fever tends to be self-limited and has no significant complications. The symptoms usually resolve within a week with no remaining effects.

Legionnaires' Disease and Pontiac Fever (Legionellosis) Causes

Both Legionnaires' disease and Pontiac fever are caused by the Legionella bacterium. Not everyone exposed to the Legionella bacteria will get ill.

Risk factors to develop the disease are

  • a weakened immune system (due to a disease, such as cancer or HIV/AIDS, or medications that suppress the immune system);
  • smoking;
  • chronic lung disease;
  • age over 50; and
  • chronic illnesses, such as diabetes, cancer, and kidney or liver failure.

Patients with the above risk factors tend to be at risk for other infections as well and need to be very alert to the onset of new signs or symptoms and especially illnesses with fever, along with additional symptoms such as weakness, confusion, and shortness of breath.

Traveling has been identified as an additional risk factor for contracting Legionnaires' disease. These cases have been linked to contaminated water supplies in hotels and cruise ships.

Bacterial Infections 101 Types, Symptoms, and Treatments Slideshow

Bacterial Infections 101 Types, Symptoms, and Treatments Slideshow

Bacteria are microscopic, single-cell organisms that live almost everywhere. Bacteria live in every climate and location on earth. Some are airborne while others live in water or soil. Bacteria live on and inside plants, animals, and people. The word "bacteria" has a negative connotation, but bacteria actually perform many vital functions for organisms and in the environment. For example, plants need bacteria in the soil in order to grow.

The vast majority of bacteria are harmless to people and some strains are even beneficial. In the human gastrointestinal tract, good bacteria aid in digestion and produce vitamins. They also help with immunity, making the body less hospitable to bad bacteria and other harmful pathogens. When considering all the strains of bacteria that exist, relatively few are capable of making people sick.

REFERENCE:

Kasper, D.L., et al., eds. Harrison's Principles of Internal Medicine, 19th Ed. United States: McGraw-Hill Education, 2015.

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