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An outbreak of Legionnaires’ disease that hospitalized 90 people and killed seven others has ended, according to the New York City Health Department.
This recent outbreak raises questions about Legionnaires’ disease. What causes the disease, and how serious is it? What symptoms do infected people exhibit, and who should be most concerned about the disease? How is it transmitted? How is the disease diagnosed and treated? And how can it be prevented?
To help with these questions, I spoke with CNN wellness expert Dr. Leana Wen. Wen is an emergency physician and clinical associate professor at George Washington University. She previously was Baltimore’s health commissioner.
CNN: What causes Legionnaires’ disease, and how serious is it?
Dr. Leana Wen: Legionnaires’ disease is a form of severe pneumonia caused by the Legionella bacteria. This bacteria can also cause a milder, flu-like illness called Pontiac fever. While people with Pontiac fever can often recover without specific treatment, untreated Legionnaires’ is extremely serious and can be fatal.
The case-fatality rate of Legionnaires’ is about 10%, according to the US Centers for Disease Control and Prevention. That means 1 in 10 people who fall ill due to this disease will die. For individuals who contract the disease in health care settings, the case-fatality rate is as high as 25%, the CDC says.
CNN: What symptoms do infected people exhibit?
Wen: The symptoms of Legionnaires’ disease can include cough, high fever, shortness of breath, headaches and muscle aches. Some patients may have gastrointestinal symptoms such as diarrhea, nausea and abdominal pain. Some also exhibit neurological symptoms such as confusion.
These symptoms start within two to 14 days after exposure to the Legionella bacteria. Legionnaires’ can lead to severe complications, including lung failure requiring mechanical ventilation, kidney failure, total body infection resulting in septic shock, and death.
CNN: Who should be most concerned about the disease?
Wen: Not everyone exposed to the Legionella bacteria will develop Legionnaires’ disease. Risk factors for becoming ill include significant underlying medical conditions such as chronic lung disease, kidney disease, diabetes, cancer and immunodeficiency. A current or past history of smoking also increases risk of severe illness, as does being 50 years or older.
CNN: How is the disease transmitted?
Wen: Unlike many types of pneumonia, Legionnaires’ disease is not transmitted directly from person to person.
The Legionella bacteria are found naturally in bodies of water like lakes and rivers and in soil. People can become infected by breathing in aerosolized mist containing the bacteria or by accidentally aspirating contaminated water into their lungs. Outbreaks are often tied to contaminated air, water, and heating and cooling systems. For instance, past outbreaks have occurred in hotels, cruise ships, hospitals and nursing homes.
CNN: What was the cause of the outbreak in New York City, and how do authorities know that cluster is over?
Wen: The New York City Health Department performed a thorough investigation in the areas where the Legionnaires’ cases occurred. This included testing water from cooling towers in large buildings. In this case, they found that the Legionella bacteria strain infecting patients matched the strain found in the cooling towers in two buildings. These facilities agreed to and completed full cleaning and disinfection procedures to prevent the bacteria from growing and infecting others.
August 9 was the last day that a person who had symptoms of Legionnaires’ disease was diagnosed. On August 29, just under three weeks since the last diagnosis, the Health Department declared that the community cluster had officially ended. This means that there should not be new cases due to Legionnaires’ disease from this outbreak.
CNN: How is the disease diagnosed and treated?
Wen: The preferred method for diagnosing Legionnaires’ disease is a combination of a respiratory specimen test and a urine test, according to the CDC. The respiratory specimen can be obtained through the sputum. The urine test looks for a piece of the Legionella bacteria.
Antibiotics are key to treatment of Legionnaires’. Depending on factors such as the patient’s clinical condition and preexisting conditions and whether the infection was acquired in the hospital or in the community, the antibiotic choices could include one or multiple drugs such as levofloxacin, azithromycin, doxycycline and rifampin. Individuals will also receive supportive treatment as needed. For instance, those who need additional breathing support may require oxygen support or a machine to breathe for them.
CNN: How can Legionnaires’ disease be prevented?
Wen: It’s important to emphasize that most healthy people exposed to Legionella bacteria will not become ill. However, some can, and those with risk factors can certainly become very sick.
There are two important components of reducing risk from Legionnaires’. The first is recognizing that infection can be random — for instance, by simply by working in the garden when the soil happens to carry the Legionella bacteria or using a contaminated hot tub. Patients should be sure to report symptoms to their clinicians, and clinicians need to be vigilant and consider Legionnaires’ disease as a possibility.
The second is taking preventive measures to reduce the risk of Legionella being spread in water systems. People who oversee water management programs for apartments, hotels, long-term care facilities and other large buildings should take steps recommended by the CDC — such as identifying areas where Legionella could grow and spread and implementing control measures.
They should be vigilant about preventive methods such as regularly flushing the water system, cleaning decorative water features, disinfecting hot tubs, and ensuring that cooling towers are clean and well-maintained.