Patients with listeriosis often have an increase in peripheral blood leukocytes, predominantly neutrophilic. The clinical presentation is variable, with the main clinical types being septic meningoencephalitis, septicemia, and perinatal infections leading to miscarriage or neonatal listeriosis. The disease is found throughout the world. Listeria monocytogenes can be isolated from soil, water and vegetable surfaces, and from human and animal feces. People are infected through direct contact with infected animals, with a sporadic distribution. Infections by this mode of transmission are more common in butchers, slaughterhouse workers and veterinarians, with some occupational relationship. The bacteria can also be spread through the digestive tract by contaminating vegetables, milk, and other foods, causing outbreaks of epidemic human Listeriosis. The bacteria can also cause nosocomial infections. Normal individuals have some natural immunity to Listeria monocytogenes infection. Infections tend to present with only flu-like symptoms or mild meningoencephalitis. The course of the disease is often benign and self-limiting. When human immune function is low, especially phagocytosis and cellular immunity, bacteria enter small local veins or lymphatic vessels via intestinal mucosa or skin and mucosa, and subsequently invade blood circulation, causing sepsis. When bacteria invade tissues and organs, they can cause purulent lesions in the corresponding tissues and organs, forming small scattered abscesses. Invasion of brain tissue and meninges can cause purulent meningoencephalitis and even brain abscess. When pregnant women are infected, the bacteria can pass through the placenta and cause embryonic infection, resulting in miscarriage or neonatal listeriosis.