Yersinia is a genus of bacteria that includes several species, some of which can cause serious diseases in humans and animals. The most well-known species is Yersinia pestis, which is responsible for the plague. This bacterium can be transmitted through flea bites, direct contact with infected animals, or inhalation of respiratory droplets from an infected person. Another important species is Yersinia enterocolitica, which can lead to gastrointestinal infections. This bacterium is often found in contaminated food, especially undercooked pork. Symptoms of infection can include diarrhea, fever, and abdominal pain, making it crucial to practice good food safety to prevent illness.