Approximately 2000 cases per year are reported. Lower incidence figures have been reported in Australia, England, and Denmark. Neonatal infections can be subdivided into early onset and late onset disease. Postnatal infections usually occur in immunocompromised children and are less common than neonatal infections. Listeriosis is suggested in cases of neonatal sepsis or meningitis and in cases of sepsis or meningitis in children who are immunocompromised.
Listeria is acquired by ingestion of contaminated food products.
Mothers who acquire Listeria may complain of influenzalike illnesses with headache, malaise, fever, and chills. Mothers with Listeria infections also may develop premature labor. Infants with Listeria can be classified as early onset and late onset infection. Meconium stained amniotic fluid is common in newborns with early onset Listeria. Respiratory difficulty is common including a history of cyanotic episodes, rapid breathing, and grunting.