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Delaware Health Alert Network #35

July 11, 2003 4:51 pm

Health Update

Delaware's Division of Public Health (DPH) is correcting inaccurate information that was issued yesterday. One individual has died of Legionnaires' disease in Delaware, not two as previously reported. This error occurred because of misinformation DPH received from the hospital that reported a death incorrectly.

The individual who was previously reported to be deceased is an out-of-state resident who was discharged from the treating hospital. That individual has recovered and returned home.

Below is the Health Advisory as it was originally sent on July 10, 2003.
Delaware Health Advisory
Increased Reports of Legionnaires' Disease In Delaware and Mid-Atlantic States

The Delaware Division of Public Health is investigating an increase in reported cases of Legionnaires' disease. At this time, the cases appear to be sporadic. No common source of exposure has been identified. DPH is continuing its investigation into these cases.

Nine cases of Legionnaires' disease among Delaware residents have been reported to DPH since June 2003. Dates of diagnosis range from May 29 to July 5. All patients were hospitalized, and there has been one fatality. Seven patients are residents of New Castle County and two are from Sussex County. The average age is 55 years (range: 41-71 years).

Three additional non-Delaware residents were hospitalized in Delaware for Legionnaires' disease during this same time frame, one of whom expired.

During 1995-2002, an average of 13.8 cases of Legionnaires' disease have been reported to DPH per year (range: 6-22 cases). Prior to June, there were no cases reported in 2003.

According to reports to the Centers for Disease Control and Prevention (CDC), the south Atlantic region (Delaware, Maryland, District of Columbia, Virginia, West Virginia, North Carolina, South Carolina, Georgia, Florida) has reported 161 cases of Legionnaires' disease thus far in 2003, compared to 89 cases in 2002. To date, no common sources of infection have been reported from these states.

Etiologic Agent

Legionnaires' disease is caused by the bacterium Legionella pneumophila and other Legionella species. At least 46 species and 68 serogroups have been identified. L. pneumophila, an ubiquitous aquatic organism that thrives in warm environments (32° - 45°C), causes over 90% of Legionnaires' disease in the United States.

Mode of Transmission

Outbreaks of Legionnaires' disease have occurred after persons have inhaled mists that come from a water source (e.g., air conditioning cooling towers, whirlpool spas, showers) contaminated with Legionella bacteria. Persons may be exposed to these mists in homes, workplaces, hospitals or public places. Legionnaires' disease is not transmitted from person to person, and there is no evidence of persons becoming infected from auto air conditioners or household window air-conditioning units. The incubation period for Legionnaires' disease is two to ten days.

Clinical Symptoms

The disease has two distinct forms: Legionnaires' disease, a more severe infection that includes pneumonia; and Pontiac fever, a milder flu-like illness. Symptoms of Legionnaires' disease are typical of any bacterial pneumonia, including fever, chills, and cough, which can be either productive or nonproductive. Some patients also experience myalgias, headache, fatigue, anorexia, and occasionally diarrhea. In addition, mental status changes and hyponatremia may develop. Approximately 5-15% of cases are fatal.

Risk Groups

While Legionnaires' disease can affect any age group, middle-aged and older persons are at highest risk, particularly if they smoke cigarettes or have chronic lung disease. Also at increased risk are immunocompromised persons (such as those with cancer, kidney failure requiring dialysis, diabetes or AIDS), as well as those who take immunosuppressant medications.


Specific laboratory tests are required to differentiate Legionnaires' disease from other causes of pneumonia. Sputum or other respiratory samples can be sent for gram stain and culture, or for direct fluorescent antibody (DFA) testing. Serologic samples (acute and chronic, obtained 3-6 weeks apart) and urine samples can be sent for antibody testing.


Erythromycin is the antibiotic currently recommended for treating persons with Legionnaires' disease. A second drug, rifampin, may be used in addition in severe cases. Other drugs are available for patients unable to tolerate erythromycin.


There are no specific measures available to prevent individuals from contracting Legionnaires' disease. Improved design and maintenance of cooling towers and plumbing systems to limit the growth and spread of Legionella organisms are the foundations of Legionnaires' disease prevention.


Legionnaires' disease is a reportable disease in Delaware. Please report all cases to the Division of Public Health at 888-295-5156.

For more information about Legionnaires' disease, please contact DPH at 888-295-5156 or refer to

Categories of Health Alert messages:

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