(CNN) — This week, officials confirmed 18 cases of Legionnaires' disease in Marshall County . This comes after an outbreak this summer in New York that led to seven deaths and 114 confirmed cases of the illness.

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, CNN 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 s

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