Listeriosis  
Annual Summary of Reportable Diseases

• In 2023 there was an average number of cases with no deaths or outbreaks. 

Nine culture-confirmed listeriosis cases were reported in 2023. Eight (89%) cases were hospitalized, and none died. The median age of cases was 69 years (range, 28 to 88 years). Eight (89%) cases had Listeria monocytogenes isolated from blood and one from cerebrospinal fluid. There were no pregnancy-associated cases among culture-confirmed cases in 2023. All nine cases reported white race; one was of Hispanic ethnicity. The nine cases reported in 2023 were equal to the median number of cases reported from 1996 through 2022 (range, 3 to 19). No 2023 cases were part of recognized outbreaks.

In 2019, national case definitions were modified to include “probable” and “suspected” cases of listeriosis. In 2023, two suspected cases were identified in individuals with L. monocytogenes isolated from non-sterile sites (drainage, buttock) at a clinical laboratory. 

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Twelve culture-confirmed listeriosis cases were reported in 2022. Eleven (92%) were hospitalized, and two (17%) died. The median age of cases was 72 years (range, 14 to 95 years). Eleven (92%) cases had Listeria monocytogenes isolated from blood and one from peritoneal fluid. There were no pregnancy-associated cases among culture-confirmed cases in 2022. Seven cases were white, three were Black, one was Asian, and one reported another race; one was of Hispanic ethnicity. The 12 cases were slightly greater than the median number of cases reported from 1996 through 2021 (median, 9 cases; range, 3 to 19). One 2022 case was part of a Florida outbreak associated with commercially distributed ice cream, and one 2022 case (who was not hospitalized) was linked to Listeria-based cancer immunotherapy.

In 2019, national case definitions were modified to include “probable” and “suspected” cases of listeriosis. In 2022, one suspected case was identified in an individual with L. monocytogenes isolated from an elbow swab at a clinical laboratory.

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Twelve culture-confirmed listeriosis cases were reported in 2021. All were hospitalized, and three died. The median age of cases was 68 years (range, 44 to 93 years). Ten (83%) cases had Listeria monocytogenes isolated from blood and two from cerebrospinal fluid (CSF). There were no pregnancy-associated cases among culture-confirmed cases in 2021. Nine cases were white, two were Asian, and three were Black; none were of Hispanic ethnicity. The 12 cases are slightly greater than the median number of cases reported from 1996 through 2020 (median, 8 cases; range, 3 to 19). Three cases were part of outbreaks in 2021; two cases were part of a multi-state outbreak associated with an unknown commercially distributed vehicle, and one 2021 case was part of a multi-state outbreak associated with leafy greens that occurred from 2014 to 2022.

In 2019, national case definitions were modified to include “probable” and “suspected” cases of listeriosis. In 2021, three probable or suspected cases were identified. Two probable cases were a maternal-neonate pair; the neonate had a CSF specimen test positive by a culture-independent diagnostic test that was not subsequently culture-confirmed at the MDH PHL, and the mother was not tested. One suspected case was identified in an individual with L. monocytogenes isolated from an ankle swab at a clinical laboratory.

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Sixteen confirmed listeriosis cases were reported in 2020. All were hospitalized, and 4 died. The median age of cases was 69 years (range, 15 to 93 years). Fifteen (94%) cases had Listeria monocytogenes isolated from blood, and 1 from cerebrospinal fluid. There were no pregnancy-associated cases in 2020. Thirteen cases were white, 1 was Native Hawaiian/Pacific Islander, 1 reported other race, and 1 had unknown race; 1 was of Hispanic ethnicity. The 16 cases were the same number as reported in 2019, but twice the median number of cases reported from 1996 through 2019 (median, 8 cases; range, 3 to 19). Two cases were part of a multi-state outbreak associated with an unknown commercially distributed vehicle; the Minnesota cases were part of a restaurant subcluster, which was the first outbreak of invasive listeriosis associated with a restaurant reported in Minnesota.

In 2019, national case definitions were modified to include “probable” and “suspected” cases of listeriosis. In 2020, 1 suspected case was identified in an individual with L. monocytogenes isolated from a leg wound

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Sixteen listeriosis cases were reported in 2019. All were hospitalized, and 3 died. The median age of cases was 65 years (range, newborn to 94 years). Twelve (75%) had Listeria monocytogenes isolated from blood, 1 from cerebrospinal fluid, 1 from peritoneal fluid, 1 from pleural fluid, and 1 from a joint aspirate. Three cases were pregnancy-associated: two pregnant women who had a positive culture from blood, one who was still pregnant at 27 weeks and one who suffered a fetal demise; and a neonate who had a positive culture from blood and who survived. Eleven cases were white, 2 were Asian, 1 was black, 1 reported other race, and 1 had unknown race; 1 was of Hispanic ethnicity. The 16 cases was twice the median number of cases reported from 1996 through 2017 (median, 8 cases; range, 3 to 19). No cases were part of recognized outbreaks in 2019.

In 2019, national case definitions were modified to include “probable” cases of listeriosis. In 2019, 3 probable cases were identified: two were a mother/ infant pair where a blood specimen from the mother was culture-independent test positive at a clinical laboratory, but had no growth at the PHL and could not be tested; and, one was the mother of the culture-positive newborn who was not tested but was assumed to be infected.

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Nine listeriosis cases were reported in 2018. All were hospitalized, and 2 died. The median age of cases was 75 years (range, newborn to 92 years). Five had Listeria monocytogenes isolated from blood, 2 from pleural fluid, 1 from cerebrospinal fluid (CSF), and 1 from bile. Two cases were pregnancy-associated; both were neonates who had a positive culture from blood and who survived. Eight cases were white, and 1 was Asian/Pacific Islander; none were of Hispanic ethnicity. The 9 cases was similar to the median number of cases reported from 1996 through 2017 (median, 7.5 cases; range, 3 to 19). In 2018, 1 case was part of a multistate outbreak of 10 cases in 7 states associated with avocadoes.

In 2018, 1 case with L. monocytogenes isolated from a stool specimen was reported. The case was tested as part of a stool donation program, reported no symptoms, and was not included in official case counts; however, the isolate was closely related to a national case isolate by whole genome sequencing.

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• Archive of Annual Summary of Communicable Diseases Reported to the Minnesota Department of Health
  Archive of past summaries (years prior to 2023 are available as PDFs).