Listeria outbreaks cause maternal and perinatal mortality and morbidity: we must do better

Reports of the global threat of listeriosis to public health are increasing in number, despite the availability of effective antibiotic treatments. Listeria monocytogenes has an intracellular lifecycle and multiplies rapidly, infecting adjacent cells, undetected by antibodies in the extracellular fluid.1Southwick FS Purich DL Intracellular pathogenesis of listeriosis.N Engl J Med. 1996; 334: 770-776Crossref PubMed Scopus (239) Google Scholar Found in animal and human faeces, it can contaminate raw meat, and processed and prepared foods. The US Centers for Disease Control and Prevention recently reported a listeria outbreak in six states.2Centers for Disease Control and PreventionListeriosis investigation details.https://www.cdc.gov/listeria/outbreaks/deli-11-22/details.htmlDate accessed: November 12, 2022Google Scholar As of Nov 9, 2022, 16 people were infected, although true numbers might be higher; of those with information available, 13 people were hospitalised, including one pregnancy loss and one adult death.2Centers for Disease Control and PreventionListeriosis investigation details.https://www.cdc.gov/listeria/outbreaks/deli-11-22/details.htmlDate accessed: November 12, 2022Google Scholar In the UK, 14 linked cases of listeriosis have been identified since 2020, including eight since January, 2022, one of whom was pregnant.3Food Standards AgencyVulnerable consumers advised of ongoing risk of Listeria associated with ready to eat smoked fish. Aug 30, 2022.https://www.food.gov.uk/news-alerts/news/vulnerable-consumers-advised-of-ongoing-risk-of-listeria-associated-with-ready-to-eat-smoked-fishDate accessed: November 11, 2022Google Scholar According to WHO, listeriosis has an annual incidence of 0·1 to 10 cases per million.4WHOListeriosis. Feb 20, 2018.https://www.who.int/news-room/fact-sheets/detail/listeriosisDate accessed: November 12, 2022Google Scholar Most have mild gastroenteritis that resolves within a few days. In the recent US outbreak, cases were linked to delicatessen meat; in the UK, most people who had listeriosis reported eating ready-to-eat smoked fish. Food-borne listeria outbreaks occur frequently, highlighting the need for constant vigilance.5Sebastianski M Bridger NA Featherstone RM Robinson JL Disease outbreaks linked to pasteurized and unpasteurized dairy products in Canada and the United States: a systematic review.Can J Public Health. 2022; 113: 569-578Crossref PubMed Scopus (1) Google Scholar, 6Khsim IEF Mohanaraj-Anton A Horte IB et al.Listeriosis in pregnancy: an umbrella review of maternal exposure, treatment and neonatal complications.BJOG. 2022; 129: 1427-1433Crossref PubMed Scopus (2) Google Scholar Clinically vulnerable individuals infected with listeriosis are at risk of severe illness, including meningitis and sepsis. This group includes adults older than 65 years; those with comorbidities, such as cancer, liver failure, or kidney failure; and immunosuppressed individuals.2Centers for Disease Control and PreventionListeriosis investigation details.https://www.cdc.gov/listeria/outbreaks/deli-11-22/details.htmlDate accessed: November 12, 2022Google Scholar As pregnancy reduces cell-mediated immunity, maternal listeriosis can be asymptomatic; if undetected and untreated, infection could lead to miscarriage, stillbirth, preterm birth, or life-threatening neonatal infection presenting with sepsis or meningitis.2Centers for Disease Control and PreventionListeriosis investigation details.https://www.cdc.gov/listeria/outbreaks/deli-11-22/details.htmlDate accessed: November 12, 2022Google Scholar, 4WHOListeriosis. Feb 20, 2018.https://www.who.int/news-room/fact-sheets/detail/listeriosisDate accessed: November 12, 2022Google Scholar, 7Xu L Du Y Wu Y Neglected listeria infection in pregnancy in China: 93 cases.J Matern Fetal Neonatal Med. 2022; 35: 9549-9557Crossref PubMed Scopus (0) Google Scholar Listeriosis is reported to be 12–20 times more prevalent in pregnancy than in the general population,8Elinav H Hershko-Klement A Valinsky L et al.Pregnancy-associated listeriosis: clinical characteristics and geospatial analysis of a 10-year period in Israel.Clin Infect Dis. 2014; 59: 953-961Crossref PubMed Scopus (43) Google Scholar although some of this prevalence might be due to increased identification during pregnancy. A recent systematic review including around 500 pregnant women infected with listeriosis found that diagnosis was primarily by bacterial culture; infection was most common in the third trimester (66%); symptoms were similar to influenza, including fever and fatigue; and patients were treated with intravenous amoxicillin or ampicillin.6Khsim IEF Mohanaraj-Anton A Horte IB et al.Listeriosis in pregnancy: an umbrella review of maternal exposure, treatment and neonatal complications.BJOG. 2022; 129: 1427-1433Crossref PubMed Scopus (2) Google Scholar Neonatal listeriosis is categorised as early onset (ie, ≤2 weeks after birth, probably caused by intrauterine exposure) or late-onset (ie, >2 weeks after birth; could also be due to early postnatal exposure). During a large outbreak in Spain in 2019, 207 cases were confirmed; the median age of those affected was 44 years (range 0–94), and 114 (55%) were women. Most (n=154) had mild gastroenteritis, 141 (68%) required hospitalisation and three died; five of 34 pregnant women had a miscarriage.9Fernández-Martínez NF Ruiz-Montero R Briones E et al.Listeriosis outbreak caused by contaminated stuffed pork, Andalusia, Spain, July to October 2019.Euro Surveill. 2022; 27: 2200279Crossref PubMed Scopus (0) Google Scholar In a 2017 outbreak in South Africa,10Thomas J Govender N McCarthy KM et al.Outbreak of listeriosis in South Africa associated with processed meat.N Engl J Med. 2020; 382: 632-643Crossref PubMed Scopus (86) Google Scholar 465 (50%) of 937 cases were associated with pregnancy, 406 (87%) of which occurred in neonates. 77 (38%) of the pregnancy-associated cases and 97 (46%) of the remaining patients were HIV positive. Concerningly, 193 (27%) of 728 patients with known outcomes died, including 28% of neonates and 8% of pregnant women, highlighting the disproportionate outcomes in different countries.10Thomas J Govender N McCarthy KM et al.Outbreak of listeriosis in South Africa associated with processed meat.N Engl J Med. 2020; 382: 632-643Crossref PubMed Scopus (86) Google Scholar Severe adverse outcomes have also been observed outside outbreak settings. A retrospective US cohort11Craig A Federspiel J Wein L Thompson J Dotters-Katz S Maternal and obstetric outcomes of listeria pregnancy: insights from a national cohort.J Matern Fetal Neonatal Med. 2022; 35: 10010-10016Crossref PubMed Scopus (1) Google Scholar study of 134 pregnant women hospitalised with listeriosis during 2007–18 reported higher rates of severe maternal morbidity than in those without listeriosis (30·9% vs 1·6%, respectively; p<0·001; 21·2-fold higher adjusted risk; 95% CI 14·0–31·9) including acute respiratory distress syndrome (2·8% vs 0·1%, respectively; p<0·001), mechanical ventilation (1·4% vs 0·0%, respectively; p<0·001), sepsis (28·1% vs 0·1%, respectively; p<0·001), and shock (1·4% vs 0·0%, respectively; p<0·001). Pregnant women with listeria also had higher rates of caesarean delivery, as compared with those who did not (57·9% vs 32·9%, respectively; p<0·001), preterm birth (61·3% vs 7·7%, respectively; p<0·001), and stillbirth (13·5% vs 0·7%, respectively; p<0·001).11Craig A Federspiel J Wein L Thompson J Dotters-Katz S Maternal and obstetric outcomes of listeria pregnancy: insights from a national cohort.J Matern Fetal Neonatal Med. 2022; 35: 10010-10016Crossref PubMed Scopus (1) Google Scholar The US Food and Drug Administration warns that symptoms can develop within a few hours or as late as 2–3 days after eating contaminated food, although intervals of up to 3 months have been reported. Real-time PCR from bacterial isolates should be used for rapid and accurate diagnosis. Pregnancy-related listeriosis can result in fetal death in 20–30% of cases,8Elinav H Hershko-Klement A Valinsky L et al.Pregnancy-associated listeriosis: clinical characteristics and geospatial analysis of a 10-year period in Israel.Clin Infect Dis. 2014; 59: 953-961Crossref PubMed Scopus (43) Google Scholar although this percentage might be biased by under-reporting of milder cases. Thus, in pregnant women, adequate antibiotic treatment and, depending on disease severity and gestation, immediate delivery might improve outcomes for the baby. This recent listeria outbreak, like the COVID-19 pandemic and 2022 mpox (formerly known as monkeypox) outbreak, highlights the need to continually review and update guidelines for infectious diseases in pregnancy. Only 26% of pregnant women with listeria infection present with fever, and current recommendations might lead to many going undiagnosed, potentially placing fetuses at risk.8Elinav H Hershko-Klement A Valinsky L et al.Pregnancy-associated listeriosis: clinical characteristics and geospatial analysis of a 10-year period in Israel.Clin Infect Dis. 2014; 59: 953-961Crossref PubMed Scopus (43) Google Scholar We continue to advocate for investment in guidance, surveillance, and research in countries with high incidence, so that both local and international communities can benefit from evidence-based management of rare infectious diseases. High-risk populations, and in particular pregnant women and young infants, should not be excluded from treatment and prevention trials. We declare no competing interests.