Listeriosis is currently the third leading cause of death from food poisoning in the United States. Unlike other foodborne pathogens, the Listeria monocytogenes bacterium can cross the placenta of a pregnant woman and also infect a fetus. The population groups considered to be the most vulnerable to a Listeria infection are pregnant women, newborn infants, adults aged 65 and older and individuals with weakened immune systems. Older adults are four times as likely as younger adults to contract listeriosis over half of those diagnosed with a Listeria infection are age 65 or over. The risk for listerosis increases tenfold in both pregnant women and cancer patients, and people on dialysis are 50 times more likely to become infected. Symptoms of a Listeria infection usually begin about one to four weeks after exposure. Listeriosis often presents with flu-like symptoms, which may include fever, muscle aches, diarrhea and mild nausea. Some people, particularly elderly adults, may experience a headache, stiff neck, confusion, loss of balance or convulsions. Infection during pregnancy can result in miscarriage, stillbirth, low birth weight and/or preterm labor. In immunocompromised individuals and neonates, listeriosis commonly manifests as an invasive infection, such as sepsis, meningitis, meninencephalitis or granulomatosis infantiseptica. Listeriosis is diagnosed through a bacterial culture taken from a body tissue or fluid (blood, cerebrospinal fluid, placenta). A stool culture is not recommended as a screening tool for listeriosis. Once diagnosed, the Listeria infection is treated with antibiotics.