Hospital: Report invasive disease by phone or mail, send isolate to State Hygienic Lab (SHL) - (319) 335-4500
Lab: Report invasive disease by IDSS, phone or mail, send isolate to SHL - (319) 335-4500
Physician: Report by IDSS, facsimile, mail, or phone
Local Public Health Agency (LPHA): Follow up required
Hospital Infection Preventionist: Follow up required
Iowa Department of Public Health
Disease Reporting Hotline: (800) 362-2736
Secure Fax: (515) 281-5698
Listeriosis is caused by the bacterium Listeria monocytogenes.
B. Clinical Description
Listeriosis is typically manifested as meningoencephalitis or bacteremia in newborns and adults. It may cause fever and spontaneous abortion in pregnant women. Symptoms of meningoencephalitis include fever, headache, stiff neck, nausea and vomiting. The onset may be sudden or, in the elderly and in those who are immunocompromised, it may be more gradual. Delirium and coma may occur. Newborns, the elderly, immunocompromised persons, and pregnant women are most at risk for severe symptoms. Infections in healthy persons may be asymptomatic or only amount to a mild flu-like illness. Papular lesions on hands and arms may occur from direct contact with infectious material. The case-fatality rate in infected newborn infants is about 30% and approaches 50% when onset occurs in the first 4 days of life.
Principal reservoir for L. monocytogenes is in soil, forage, water, mud and silage. Other reservoirs include mammals, fowl and people. Soft cheeses may support the growth of Listeria during ripening and have caused outbreaks. Unlike most other foodborne pathogens, Listeria can multiply at refrigerator temperatures.
D. Modes of Transmission
Listeriosis may be acquired by the fetus in utero or during passage through the birth canal. Listeriosis can also be transmitted through ingestion of contaminated foods, especially pasteurized soft cheeses and ready-to-eat foods.
E. Incubation Period
Variable; outbreak cases have occurred 3 - 70 days following a single exposure to an implicated product. Median incubation is estimated to be 3 weeks.
F. Period of Communicability or Infectious Period
Although Listeria may be shed for several months in the stool of infected persons, person-to-person transmission is rare. Following delivery, mothers of infected newborns may shed Listeria for 7 - 10 days in vaginal secretions or urine.
Listeria is widely distributed in nature. Most cases of human listeriosis are believed to occur sporadically, but foodborne and healthcare associated outbreaks have been documented. Foods associated with infection include unpasteurized milk, soft cheeses, processed meats and contaminated vegetables. Newborns, the elderly, immunocompromised persons and pregnant women are at greater risk of infection. CDC estimates that approximately 1600 illnesses and 260 deaths due to listeriosis occur annually in the United States. About 30% of diagnosed cases occur within the first 3 weeks of life.
H. Bioterrorism Potential
I. Additional Information
The Council of State and Territorial Epidemiologists (CSTE) surveillance case definitions for Listeriosis can be found at: www.cdc.gov/osels/ph_surveillance/nndss/phs/infdis.htm#top
CSTE case definitions should not affect the investigation or reporting of a case that fulfills the criteria in this chapter. (CSTE case definitions are used by the state health department and the CDC to maintain uniform standards for national reporting.
American Academy of Pediatrics. 2003 Red Book: Report of the Committee on Infectious Diseases, 26th Edition. Illinois, Academy of Pediatrics, 2003.
CDC Website. Listeriosis: www.cdc.gov/listeria/index.html
Heymann, D.L., ed. Control of Communicable Diseases Manual, 20th Edition. Washington, DC, American Public Health Association, 2015.
Iowa Administrative Code (641) Chapter 1 Notification & Surveillance of Reportable Communicable & Infectious Diseases,
Poisonings & Conditions.
Iowa Division of Inspections and Appeals, Food Inspections www.profoodsafety.org/
State Hygienic Laboratory at the University of Iowa www.shl.uiowa.edu