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Description:This light photomicrograph depicted cytoarchitectural details seen in a lung tissue specimen from a Knoxville patient with fatal pneumonia due to Legionnaires’ disease. The tissue was stained using Dieterle’s silver stain, which employs a silver-impregnation staining technique, the results of which reveals the presence of Legionella pneumophila bacteria.

Legionellosis disease has two distinct forms:

-Legionnaires' disease, the more severe form of infection which includes pneumonia, and

-Pontiac fever, a milder illness.

What is Legionnaires’ disease?

Legionnaires’ disease (LEE-juh-nares) is caused by a type of bacteria called Legionella. This bacterium got its name in 1976, when many people who went to a Philadelphia convention of the American Legion suffered from an outbreak of this disease, a type of pneumonia (lung infection). Although this type of bacteria was around before 1976, more Legionnaires’ disease illness is being detected, due to the fact that we are now looking for this disease whenever a patient presents with a case of pneumonia.

Each year, between 8,000 and 18,000 people are hospitalized with Legionnaires' disease in the U.S. However, many infections are not diagnosed or reported, so this number may be higher. More illness is usually found in the summer and early fall, but it can happen any time of year.

High Resolution: Click here for hi-resolution image (6.57 MB)
Content Providers(s):CDC/ Dr. William Cherry
Creation Date:1978
Photo Credit:
Links:CDC - National Center for Immunization and Respiratory Diseases; Legionellosis Resource Site (Legionnaires' Disease and Pontiac Fever); Patient Facts: Learn More about Legionnaires' disease
CDC Organization
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Copyright Restrictions:None - This image is in the public domain and thus free of any copyright restrictions. As a matter of courtesy we request that the content provider be credited and notified in any public or private usage of this image.