Echinococcosis is a parasitic disease caused by tapeworms that are transmitted to humans from animals. Infection occurs when humans ingest parasite eggs in contaminated food, water, or soil, or through direct contact with infected animals. This disease occurs in four forms, although the two most important forms to humans are cystic echinococcosis and alveolar echinococcosis. Signs and symptoms of alveolar echinococcosis include an incubation period of 5-15 years, and the slow growth of a tumor-like lesion, usually in the liver. Other symptoms include weight loss, abdominal pain, general malaise, and signs of hepatic failure. Other general symptons of echinococcosis include nausea, vomiting, and cough. Cystic echinococcosis occurs on every continent except Antarctica, and alveolar echinococcosis is located solely in the northern hemisphere, particularly the areas of China, Russia, and some countries in continental Europe and North America. Prevalence is greater in rural areas where animals are slaughtered. Echinococcosis is treatable, but often expensive and complicated to treat, and can require extensive surgery or prolonged drug therapy.