Menu Healthy Lifestyle Diseases & Conditions First Aid Symptoms Tests & Procedures Videos Definitions FAQs ListeriosisUpdated: 2020-01-18OverviewListeriosis is a potentially serious infection that can be contracted from improperly processed deli meats and unpasteurized milk products. Newborns and people with weak immune systems are most at risk.SymptomsSymptoms may not appear for 30 days or more. Symptoms may include fever, aches, nausea and diarrhea.TreatmentsSerious cases require antibiotics. © 1998-2022 Mayo Foundation for Medical Education and Research(MFMER). All rights reserved. Terms of Use