Infected animals may also serve as sources. Unlike other organisms, listeria can be spread by several different methods. Other meats such as ground beef, poultry and sausages may also be contaminated. In newborn infections, the organism may be transmitted from mother to fetus in utero, or directly to the fetus at the time of birth. Direct contact with the organism can cause lesions on the hands or arms.
Infection is also possible by inhaling the organism.
Since listeria can affect many different parts of the body, the symptoms vary. Healthy adults and children who are infected rarely become seriously ill. In most cases, listeria infection causes fever and gastrointestinal symptoms resembling many other mild illnesses. Sometimes, various types of sores at the site of infection are the primary symptom. In serious cases of listeriosis, this illness may lead to infections of the brain or blood, either of which can cause death, particularly in at risk groups.