Shigellosis

Shigellosis is a relatively uncommon disease in Europe, leading to gastrointestinal problems caused by Shigella bacteria. Yet, it is a health concern for certain population groups and in certain countries, also in the developed world. In Europe, one sixth to one third of the cases is imported by travellers (ECDC, 2014-2022). Infections occur after swallowing faecal contamination. The disease is especially affecting young children in developing countries and outbreaks are frequent in conditions with poor water supply and sanitary facility, annually leading to about 160 000 deaths worldwide (Chung The et al., 2021). Still, the disease is underreported and often misdiagnosed. Of particular concern is the multi-drug resistance of Shigella bacteria in different regions (Lampel et al., 2018).

Source & transmission

Shigellosis is primarily transmitted through faecal contamination from an infected person to the mouth of another person. Infected people who do not thoroughly wash their hands after defecation can cause new infections through direct physical contact (including sexual contact), or indirectly by contaminating food or water. In Europe, sexual transmission is a common infection route today. Patients can transmit the disease as long as the Shigella bacteria are excreted in faeces, which is generally during the acute infection but may continue for up to 4 weeks or occasionally several months.

Next to person-to-person infections, contaminated raw milk and dairy products or uncooked vegetables are other transmission routes (Gerba, 2009). Furthermore, flies can transmit Shigella bacteria from latrines to uncovered food (Gerba, 2009). Outside the human body however, Shigella can only survive for a short time (Niyogi, 2005). Remarkably, the disease can manifest itself already at very low doses of less than ten bacterial cells, which is more than ten thousand times lower than for most other bacterial infections (Chung The et al., 2016).

Outbreaks mostly occur in places where many people are together (such as in prisons, institutions for children, day-care centres or mental hospitals) especially when personal hygiene is poor, as well as among men who have sex with men (Rebmann, 2009).

Health effects

Shigella infections can have mild to severe symptoms, with some infected persons experiencing even no symptoms. If symptomatic, symptoms usually last between 4 and 7 days, and most patients recover without medical interventions except for proper rehydration. The symptoms occur fast, about one to three days after infection and include diarrhoea – often with mucus and/or blood, fever, nausea, stomach cramps and sometimes painful urination or defecation. The Shigella bacteria can also produce toxins that circulate in the blood stream of an infected person (toxaemia). In more severe cases, the stool may be bloody and slimy (dysentery) and complications may follow, such as weakened gut muscles (leading to rectal prolapse), appendicitis or a life-threatening colonic inflammation. Also, dehydration, low salt (hyponatremia) or sugar levels (hypoglycaemia) in the blood, neurological infections (meningitis), inflammation in the bones (osteomyelitis), arthritis, abscesses in the spleen or vaginal infections can result from shigellosis. Among the most dangerous clinical manifestations are seizures, neurological damages or an increase in white blood cells mimicking leukaemia. As long-term effects, patients may develop an irritable bowel syndrome, arthritis or haemolytic uremic syndrome, which affects the red blood cells, kidney and nervous system (Pacheco & Sperandio, 2012).

Morbidity & mortality

In the EEA member countries (excluding Switzerland and Türkiye due to absence of data), in the period 2007-2021:

69,100 infections (ECDC, 2023)
15 deaths and an overall mortality rate of 0.025%. Yet, mortality rates vary with bacteria strain and condition of the patient and can rise to 20% for hospitalized patients (Bagamian et al., 2020; Ranjbar et al., 2010).
Increasing incidence trend between 2015 and 2019, after a decrease in reported cases between 2007 and 2014. In 2020, the number of reported cases dropped drastically, which may have been due to underreporting and decreased exposure following the travel and social restrictions and hygienic measures associated with the COVID-19 pandemic.
Until 2019, about half of the cases was travel related. Transmission mostly happens via food, and less frequently by sexual and person-to-person contact.

(ECDC, 2014-2022)

Distribution across population

Age group with the highest disease rate in Europe: children below 5 years old, and men between 25 and 44 years old (ECDC, 2014-2022)
Groups at risk of a severe disease course: children under 10 years old, people deprived of good health care or facing food insecurity, elderly and people with a weakened immune system, (Kotloff et al., 2018; Niyogi, 2005 ; Launay et al., 2017)

Climate sensitivity

Climatic Suitability

Shigella bacteria grow best at ambient temperatures between 21 and 38°C. The optimal pH range is between 5.8 and 6.4 (Ghosh et al., 2007).

Seasonality

In Europe, most infections occur in late summer/autumn (ECDC, 2014-2022).

Climate Change Impact

Increased temperatures, rainfall amounts and air humidity both accelerate bacterial reproduction and increase the risk of contaminated (drinking) water, which may increase shigellosis infection risks. Studies in Asia suggest that changes in climatic conditions may alter the geographical distribution pattern of Shigella bacteria and increase the shigellosis infection risk (Song et al., 2018; Chen et al., 2019). This can indirectly impact the European population as part of the shigellosis infections in Europe are travel related.

Prevention & Treatment

Prevention

Awareness raising about the effectiveness of hand washing and general hygiene, particularly while traveling in regions with poor hygienic conditions or when handling food
Identification and closure of contaminated water sources
Isolation of patients in care facilities to prevent outbreaks
Surveillance systems allow for disease detection and subsequent response measures to contain outbreaks and reduce case numbers
Vaccines are in an experimental phase

(National Academies of Sciences, Engineering, and Medicine, 2020; Sciuto et al., 2021)

Treatment

Rehydration, anti-diarrheal or fever-reducing medication
Antibiotics can shorten the duration of potential transmission and illness. Multi-drug- and extensively-drug resistant strains are increasingly problematic for high-risk groups.

(Kotloff et al., 2018; CDC, 2022)

Links to further information

References

Bagamian, K. H., et al., 2020, Heterogeneity in enterotoxigenic Escherichia coli and shigella infections in children under 5 years of age from 11 African countries: A subnational approach quantifying risk, mortality, morbidity, and stunting, The Lancet Global Health 8(1), e101–e112. https://doi.org/10.1016/S2214-109X(19)30456-5

CDC, 2022, Centers for Disease Control and Climate change impact, https://www.cdc.gov. Last accessed August 2022.

Chen, C.-C., et al., 2019, Epidemiologic features of shigellosis and associated climatic factors in Taiwan, Medicine 98(34), e16928. https://doi.org/10.1097/MD.0000000000016928

Chung The, H., et al., 2021, Evolutionary histories and antimicrobial resistance in Shigella flexneri and Shigella sonnei in Southeast Asia, Communications Biology 4(1), 353. https://doi.org/10.1038/s42003-021-01905-9

Chung The, H., et al., 2016, The genomic signatures of Shigella evolution, adaptation and geographical spread, Nature Reviews Microbiology 14(4), 235–250. https://doi.org/10.1038/nrmicro.2016.10

ECDC, 2014-2022, Annual epidemiological reports for 2012-2020 – Shigellosis. Available at https://www.ecdc.europa.eu/en/shigellosis/surveillance-and-disease-data. Last accessed August 2023.

ECDC, 2023, Surveillance Atlas of Infectious Diseases. Available at https://atlas.ecdc.europa.eu/public/index.aspx. Last accessed August 2023.

Gerba, C. P., 2009, Environmentally transmitted pathogens. In Environmental microbiology, Academic Press, pp 445-484. https://doi.org/10.1016/B978-0-12-370519-8.00022-5

Ghosh, M., et al., 2007, Prevalence of enterotoxigenic Staphylococcus aureus and Shigella spp. In some raw street vended Indian foods, International Journal of Environmental Health Research 17(2), 151–156. https://doi.org/10.1080/096031207012

Kotloff, K. L., et al., 2018, Shigellosis The Lancet 391(10122), 801–812. https://doi.org/10.1016/S0140-6736(17)33296-8

Lampel, K. A., et al., 2018, A Brief History of Shigella, EcoSal Plus 8(1), 1-25, https://doi.org/10.1128/ecosalplus.ESP-0006-2017

Launay, O., et al., 2017, Safety Profile and Immunologic Responses of a Novel Vaccine Against Shigella sonnei Administered Intramuscularly, Intradermally and Intranasally: Results From Two Parallel Randomized Phase 1 Clinical Studies in Healthy Adult Volunteers in Europe, EBioMedicine, 22, 164–172. https://doi.org/10.1016/j.ebiom.2017.07.013

Niyogi, S. K., 2005, Shigellosis, The Journal of Microbiology 43(2), 133–143.

Pacheco, A. R., & Sperandio, V., 2012, Shiga toxin in enterohemorrhagic E.coli: Regulation and novel anti-virulence strategies, Frontiers in Cellular and Infection Microbiology 2, 2235-2988. https://doi.org/10.3389/fcimb.2012.00081

Ranjbar, R., et al., 2010, Fatality due to shigellosis with special reference to molecular analysis of Shigella sonnei strains isolated from the fatal cases, Iranian Journal of Clinical Infectious Diseases 5(1) 36–39.

Rebmann, T., 2009, Spotlight on shigellosis, Nursing 39(9), 59–60. https://doi.org/10.1097/01.NURSE.0000360253.18446.0f

Song, Y. J., et al., 2018, The epidemiological influence of climatic factors on shigellosis incidence rates in Korea, International Journal of Environmental Research and Public Health 15(10), 2209. https://doi.org/10.3390/ijerph15102209