吸虫, or flukes, are a type of parasitic flatworm belonging to the class Trematoda. They typically inhabit the bodies of various hosts, including humans, and can be found in organs such as the liver, lungs, and intestines. Flukes have complex life cycles that often involve multiple hosts, including snails and fish. These parasites can cause various diseases, collectively known as schistosomiasis or fluke infections, which may lead to symptoms like abdominal pain, diarrhea, and fatigue. Prevention strategies include improving sanitation and avoiding contaminated water sources, as many flukes are transmitted through aquatic environments.