Legionnaires Disease Treatment & Management

Updated: Mar 11, 2021
  • Author: Chinelo N Animalu, MD, MPH, FIDSA; Chief Editor: Michael Stuart Bronze, MD  more...
  • Print

Approach Considerations

A delay in treatment significantly increases the risk of mortality in Legionnaires disease (LD). Therefore, include empiric anti-Legionella therapy in the regimen for severe community-acquired pneumonia (CAP) and in specific cases of nosocomial pneumonia.

Although Legionella pneumonia can present as a mild illness, most patients require hospitalization with parenteral antibiotics. Most healthy hosts exhibit clinical response to treatment within 3-5 days.


Prehospital and Emergency Department Care

Prehospital care

Oxygen therapy is the mainstay of prehospital therapy in LD. Intravenous (IV) access and fluid therapy may be indicated for dehydration or septic shock. Restraints may be required for patients with altered mental status. Seizure precautions may be indicated.

Differentiating LD with multiple rigors and altered mental status from a seizure disorder may be possible only through a clinical examination.

Emergency department care

Patient management includes the following:

  • Control the airway as indicated clinically; support ventilation and oxygenation

  • Rehydrate the patient as indicated, especially in shock or diarrheal disease

  • Antipyretics may be used as indicated

  • Cardiac monitoring may be required if chest pain, hypotension, bradycardia, or other indicators are present

  • Obtain laboratory specimens (respiratory culture and urine antigen testing), chest radiographs, computed tomography (CT) scans, and cerebrospinal fluid (CSF), as indicated

  • Begin empiric antibiotic therapy

Also see the Legionella home page from the Centers for Disease Control and Prevention (CDC), as well as the Infectious Diseases Society of America/American Thoracic Society Consensus Guidelines on the Management of Community-Acquired Pneumonia in Adults. [16]


Inpatient Care

Patients with mild to moderate pneumonia are admitted to the hospital for parenteral antibiotics and supportive measures. Patients deemed to have a severe pneumonia may require admission to the intensive care unit (ICU) for closer monitoring. Quickly initiate empiric antibiotic treatment and obtain a diagnostic workup.

Close follow-up with a pulmonologist or infectious disease specialist is recommended following discharge.


Antibiotic Therapy

In milder cases, patients can be treated in an outpatient setting with oral antibiotics that are targeted against legionella and are bacterocidal, have long half-lives and achieve high lung tissue concentrations. First line agents would include levofloxacin (a fluroquinolone) and azithromycin (a macrolide) administered through the oral route. Alternative agents would include other fluroquinolone s such as ciprofloxacin, moxifloxacin, doxycycline (a tetracycline). Other macrolides would include clarithromycin, erythromycin and roxithromycin. Newer tetracyclines such as tigecycline have been used as second line agents against L pneumoniae but appears to have limited activity against L longbeachae and therefore, should be avoided if this strain is suspected. [17]

For patients with L longbeachae infection, a fluroquinolone or a macrolide should be used. Treatment duration can range from 5-10 days in mild cases.

For patients with moderate or severe infection that require hospitalization, or those who cannot tolerate oral medications, the intravenous route of administration is preferred. When patients become clinically stable and can tolerate orally, they can then be transitioned to the oral equivalent. For severe disease, a fluoroquinolone is recommended. Adding rifampin to a regimen of fluroquinolone or macrolide, has not been shown to have any additional benefits. [18]

Continue oral antibiotics on an outpatient basis for 14-21 days, depending on the severity of the presenting illness. Patients should receive close follow-up care to ensure complete resolution of their respiratory symptoms.

Patients should complete the full course of antibiotics, whether the treatment is initiated in the outpatient setting or in the hospital. 




Consultation with a pulmonologist or infectious disease specialist is strongly recommended in cases of LD. Because of the protean presentation of this disease, however, consultations with other specialists, including the following, may be required at one time or another:

  • General internist

  • Critical care specialist

  • Cardiologist

  • Gastroenterologist

  • Neurologist

  • Nephrologist

  • Oncologist

  • General surgeon


Deterrence and Prevention

Prevention and control of nosocomial legionellosis

Legionellae should be sought in hospitalized patients with an increased risk for infection and subsequent death. If 1 definite case or 2 possible cases of nosocomial LD occur among in patients, initiate an investigation for a hospital source.

Legionellae transmission can also be discouraged through the routine maintenance of cooling towers and the use of only sterile water for filling and rinsing nebulization devices. Improved design and maintenance of cooling towers and plumbing systems can also help.


Superheating water to 70-80°C, with flushing of distal sites, may help to prevent water contamination.

Copper-silver ionization units—which produce metallic ions that disrupt the bacterial cell wall, thus resulting in lysis and cell death—are very effective at eradicating legionellae; they provide sustained protection.

Ultraviolet light kills legionellae by damaging cellular deoxyribonucleic acid (DNA). This modality is effective when disinfecting localized areas, but because it provides no sustained protection, adjunctive treatments must be used.

Hyperchlorination of water is no longer recommended, because legionellae are fairly chlorine resistant, and chlorine decomposes at the higher temperatures found in the hot water systems it is used to treat.

Following reports of LD in newborns who were infected during water births, [5] the Arizona Department of Health Services issues recommendation for minimizing the risk of Legionella contamination in tubs used during the water birthing process, such as flushing out stagnant water and sediment from hoses by running hot water through it for 3 minutes before using it to fill the tub. [19]