A 67-year-old building contractor is brought to the ED by his wife. She says that he has become very confused and is suffering from watery diarrhea and a dry cough. The patient appears acutely ill, tachypneic, diaphoretic, and confused. His temperature is elevated at 38.9°C (102°F). You hear scattered, dry rales, but the remainder of the examination is unremarkable. WBC is 23,000/mm3 with a left shift; chest x-ray shows a patchy left upper lobe air-space infiltrate. Which of the following statements concerning the most likely cause of his illness is correct?
Transmission is generally person-to-person.
+The usual incubation period is in the range of weeks rather than days.
+Other complications include skin sloughing and mucosal ulcerations.
+Travel and work histories are important considerations when diagnosing this illness.
+Early empiric antibiotic therapy with intravenous Trimethoprim every 12 hours is necessary to reduce mortality, which is as high as 40% if the disease is untreated.
Many clinicians have been alerted to the possibility of Legionella infection by the characteristic and striking associations with intestinal complaints, diarrhea, and mental status changes in the setting of an atypical pneumonia. Myocarditis, pericarditis, and coma are other possible manifestations. Direct immunofluorescent sputum testing is helpful in the acute diagnosis. Indirect immunofluorescent antibody (IFA) testing is required for diagnosis. Person-to-person transmission probably does not occur, but outbreaks from point sources (water supplies, excavation work) are more common than isolated cases, making notification of health authorities important if the disease is suspected. Early empiric antibiotic therapy with intravenous erythromycin is necessary to reduce mortality, which is as high as 40% if the disease is untreated. Oral erythromycin is continued for 3 weeks to avoid relapse.