The incubation period between exposure and symptoms is quite variable (three to 70 days, with 21 days as average) and may extend up to about two months or more according to some reports. Pregnant women who are otherwise healthy usually have only minor symptoms. However, Listeria infection during pregnancy often cause problems for the fetus:
miscarriage,
stillbirth,
premature birth, or
cause infection and,
potentially, death of newborns. Breastfeeding in humans does not transmit the bacteria to newborns; however, animal studies show the organisms are transferred in breast milk of other mammalian species. Researchers consider it theoretically possible for organism transmission in human breast milk. Occasionally, localized skin infections may occur, especially in people who handle animals infected with Listeria. These skin infections rarely lead to further complications such as brain infection. How long does a Listeria infection last? Normal healthy people infected with Listeria usually recover from the infection. However, more serious infections that require antibiotic treatment may last longer. For example, if abscesses develop in the brain, the antibiotic therapy will be required for about six weeks.
