Paragonimiasis is a flatworm infection in the lungs. This infection can last for years. These parasitic worms—also called flukes or lung flukes—may infect the human lungs when a person consumes undercooked crayfish or crab infested with it. The illness resembles stomach flu and pneumonia. In rare cases, the parasite may travel to the central nervous system, making the condition even more serious. Continue reading to find out more about paragonimiasis, its symptoms, causes and treatment.