What You Need to Know:
In the past week there have been reports of a Legionnaires’ disease outbreak in northern Illinois and the New York City area, which has sickened more than 16 people. The McHenry Illinois County Health Department has confirmed nine cases of Legionnaires’ disease from several locations across the county. In the Washington Heights neighborhood of New York City, eight residents are confirmed to have the diagnosis. There have been no related deaths thus far.
Legionellosis is the term used to include Legionnaires’ disease and Pontiac fever, which are both caused by Legionella bacteria. Legionella pneumophilia infection (Legionnaires’ disease) is responsible for most disease, and is primarily transmitted by inhalation of contaminated water droplets, but may also be transmitted through aspiration of contaminated drinking water. Large plumbing systems in buildings are often conduits where Legionella grows and is released through the air to at-risk humans via droplet contact. Other common reservoirs for Legionella include hot tubs, cooling towers, and ornamental water fountains.
Risk factors for Legionellosis include age greater than 50, a present or past history of smoking, immune system disorders, chronic illness such as COPD, hepatic failure, renal failure, or diabetes, systemic malignancy, hot tub exposure, recent travel, or recent hospitalization. Symptom onset occurs between two and ten days after exposure and may include fever, cough, dyspnea, myalgias, headaches, nausea, diarrhea, and confusion.
Three tests are used to diagnose Legionnaires’ disease, including chest x-ray to confirm the presence of pneumonia, a urinalysis, and sputum culture to test for Legionella. Patients are often hospitalized while being treated with antibiotics. The death rate for patients diagnosed with Legionnaires’ disease is one in ten, usually secondary to complications. However, the death rate increases for those who acquired the disease while being cared for in a hospital or other healthcare facility to one in four.
Read more about Legionnaires’ Disease:
Harrison’s Principles of Internal Medicine, 19e: Chapter 184. Legionella Infections
CURRENT Diagnosis and Treatment: Pediatrics, 24e: Chapter 42. Infections: Bacterial & Spirochetal
Centers for Disease Control and Prevention: Legionella (Legionnaires' Disease and Pontiac Fever)