Epidemiology

Although Listeria is widespread in nature and the ingestion of L monocytogenes is relatively common, the annual incidence of listeriosis among humans is low.[10] Most cases are sporadic and are reported in high-income countries; the fatality rate may be high.[11][12][13][14][15] Incidence data in low-income countries are generally not available.[16] Listeria can be isolated from the stools of up to 5% of healthy adults, and disease may be transmitted from this population.[17]

Immunocompetent patients rarely develop disseminated disease, although they may develop a gastroenteritis syndrome. The pathogen has a predilection for neonates (age <1 month), adults (especially >50 years), pregnant women (30% of all patients), and immunocompromised people (with HIV/AIDS, cancer, hematologic malignancies, those undergoing corticosteroid treatment, or transplant recipients).[1][18][19] Impaired cellular immunity is associated with increased incidence of the disease.

In the US, laboratory-confirmed listeriosis incidence is 0.24 cases per 100,000, and the rate of pregnancy-associated listeriosis is 13 times higher than that for the general population.​[20][21]​​ Intensive monitoring and recall of potentially contaminated products has decreased the prevalence of perinatal listeriosis by 44% in the US.[17]

The relative risk of invasive listeriosis is significantly higher for Hispanic people than for non-Hispanic people, both in the general population and also in pregnant women.[22] Among Hispanic women, the crude incidence of pregnancy-associated listeriosis increased from 5.09 per 100,000 in 2004 to 2006 to 12.37 per 100,000 in 2007 to 2009.[23] Pregnancy-associated listeriosis among non-Hispanic women showed a much lower crude incidence increase for the same periods.

In Australia, from January to April 2018, an outbreak of listeriosis was reported.[24] All patients were hospitalized. Epidemiologic investigation found that the source of the outbreak was rockmelon (cantaloupe melons) from a single grower.[24]

In 2018, the European Centre for Disease Control reported on an outbreak of invasive L monocytogenes infections (confirmed by whole-genome sequencing) linked to frozen corn, and possibly to other frozen vegetables, in the UK and 4 European Union member states (Austria, Denmark, Finland, and Sweden). There have been 47 cases reported since 2015 and, as of June 2018, 9 patients have died due to or with the infection.[25]

In 2017, 2,502 confirmed cases of listeriosis were reported by 30 EU/EEA countries, with an age-standardized notification rate of 0.42 per 100 000 population.[26] In 2019, there were 222 confirmed cases of L monocytogenes infection linked to chilled pork in Spain; 3 fatalities and 6 miscarriages were reported.

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