Epidemiological update: Spread of multidrug-resistant and extensively-drug resistant Shigella in Europe

As of April 2026, seven distinct multidrug-resistant (MDR) and extensively drug-resistant (XDR) Shigella sonnei and Shigella flexneri genetic clusters associated with mainly, but not exclusively, gay, bisexual, and other men who have sex with men are circulating in the EU/EEA. These clusters are under ECDC monitoring through the European surveillance platform, EpiPulse. Cluster analysis of sequenced Shigella isolates is how extended transmission chains and ongoing circulation within and beyond sexual networks is monitored.

For the purpose of this epidemiological update, ECDC defines XDR Shigella by resistance markers for all five antibiotics used for first- and second-line treatment of Shigella infections: azithromycin, ciprofloxacin, ceftriaxone, trimethoprim-sulfamethoxazole, and ampicillin. This is in line with the US CDC definition [1]. MDR is defined as resistance to two or more antibiotics.

The increase in extensively drug-resistant Shigella sonnei infections among gay, bisexual, and other men who have sex with men was first noted during 2020−2022 (see ECDC’s Rapid Risk Assessment dated 23 February 2022), and the first Epidemiological update was published in 2023 [2, 3].  

Since 2023, the seven clusters, some longstanding and others more recently identified, have caused more than 2 300 reported infections in 12 EU/EEA countries (mainly Belgium, Denmark, France, Germany, Ireland, Luxembourg, the Netherlands, Norway, Spain, Sweden), the UK and the US.  

Genetically distinct clusters, some reflecting prolonged, sustained transmission, indicate that MDR/XDR Shigella spread has occurred through ongoing linked episodes of transmission rather than a single outbreak. 

There has been a shift in the Shigella transmission routes reported by countries to ECDC. Earlier reports most often described food- and water-borne transmission however in recent years an increasing proportion of transmission has been linked to sexual transmission particularly among gay, bisexual, and other men who have sex with men. This shift has occurred alongside rising resistance to key antibiotics, including those used when antimicrobial treatment is indicated for shigellosis. Several circulating strains among gay, bisexual, and other men who have sex with men carry genetic markers for resistance to multiple first- and second-line antibiotic classes, corresponding to the five antibiotics used for shigellosis treatment, which limits treatment options. In addition, resistance determinants for other antibiotics not used for shigellosis treatment have been identified. A resistance marker to quaternary ammonium compounds (used in disinfectants and sanitisers) has also been observed; however, the implications of this finding are not fully understood. One country has reported a Shigella flexneri carrying a carbapenemase resistance gene. Carbapenems are an important option for treating serious shigellosis when the bacterium is suspected or known to be extensively drug resistant.

Symptoms and route of infection 

Shigellosis typically presents with acute diarrhoea, abdominal pain and fever. Most infections are self-limiting but they can be severe, especially in immunocompromised individuals. In most cases, antimicrobial therapy is not required. When treatment is indicated, the choice of antibiotic should be guided by antimicrobial susceptibility test results as soon as these become available [4, 5].

Shigella is easily transmitted between people, since infection may be caused by a very small number of bacteria (the infectious dose is low). Transmission occurs through the faecal-oral route, i.e. ingestion of bacteria excreted through the faeces from someone who is infected. This may happen through close personal contact – including sexual contact and especially oral-anal contact. Transmission can also occur via contaminated surfaces, or when consuming contaminated food. Transmission is possible in for instance households, healthcare facilities, restaurants and other close contact environments.

Assessment

Antibiotic treatment for other sexually transmitted infections (STIs), such as chlamydia and gonorrhoea, may create antibiotic selection pressure on Shigella present in the gut of people being treated. This can allow resistant Shigella strains to survive and spread within sexual networks, even when shigellosis is not the treatment target. 

Further transmission of Shigella in European countries cannot be ruled out, particularly given its low infectious dose. Sexually active individuals with multiple partners, or those who engage in group sex, are more likely to become infected and may transmit the bacteria [6].

Additional outbreaks, sustained transmission, and increasing treatment challenges should be anticipated, given the current circulation of genetically distinct MDR/XDR Shigella clusters and ongoing transmission reported in several European countries and in the United States. Strengthened surveillance, targeted prevention efforts, and prudent antimicrobial use are therefore needed.

Increasing antibiotic resistance is concerning because it can limit treatment options, not only for Shigella infections. The rising prevalence of resistant strains may also facilitate further transmission and the transfer of resistance determinants between bacterial species.

As the spring and summer period starts with increased vacation travel, Pride events and other festivals, there is an increased risk for further transmission of MDR/XDR Shigella among gay, bisexual, and other men who have sex with men. International spread of MDR/XDR Shigella following mass gathering events has been documented previously [7].  

Continued EU‑level surveillance of events and clusters 

ECDC is monitoring MDR/XDR Shigella through event-based surveillance on EpiPulse, in collaboration with EU/EEA countries. EU/EEA countries are encouraged to perform bacterial isolations for susceptibility testing and sequencing for genomic surveillance and cluster detection.

The seven genetic clusters under monitoring are defined within this context as the ECDC allele address cut-off at 10 allelic distances (ADs). The address is a stepwise cluster code that groups isolates by increasing genetic similarity thresholds (AD differences at 100, 25, 10, 5 and 2 ADs) to identify whether case isolates belong to the same genetic cluster. Publicly available sequences for national comparisons representing the respective 10 AD cluster are listed below. Countries are encouraged to compare and report to ECDC if they see these strains or others with XDR or MDR and their associated transmission patterns.

1. Cluster 215.522.689, S. sonnei, repr. outbreak strains SRR38150624, SRR38150623, SRR38150622 and SRR32729844
2. Cluster 215.522.3752, S. sonnei, repr. outbreak strain ERR16843501
3. Cluster 215.522.3986, S. sonnei, repr. outbreak strain SRR35878075
4. Cluster 435.2560.3980, S. flexneri, repr. outbreak strain SRR35839556
5. Cluster 369.2094.3272, S. flexneri, repr. outbreak strain ERR15137671
6. Cluster 369.1888.2916, S. flexneri, repr. outbreak strain ERR17037467
7. Cluster 435.850.1171, S. flexneri, repr. outbreak strain ERR14995010

Recommendations for prevention and control

Avoiding sexual activity (including oral-anal contact) if diarrhoea or gastrointestinal symptoms occur, as well as consistent good personal hygiene, will also reduce the risk of transmission of MDR/XDR Shigella and other pathogens. 

Healthcare professionals can support prevention by considering sexually transmitted Shigella in relevant patients, ensuring antimicrobial susceptibility testing, and reporting cases to public health authorities. Laboratory confirmation can be challenging as Shigella can be difficult to isolate, and culture may not be attempted unless needed for antimicrobial guidance. PCR positive Shigella/EIEC results should thereby be considered in patient management, even if a Shigella isolate have not been able to be retrieved.

Strengthened epidemiological and microbiological surveillance on national and European level, together with targeted communication, and collaboration with organisations working withgay, bisexual, and other men who have sex with men ‑are also essential to raise awareness and support early detection and control.

For the public 

• Be aware Shigella can be transmitted through faecal-oral exposure during sexual activity.
• Sex in group settings or with multiple partners increases the risk for contracting a Shigella infection.
• Maintaining good personal hygiene can help reduce the risk of infection.
• If diarrhoea or gastrointestinal symptoms occur, avoid sexual activity, seek medical care, and inform clinicians that symptoms may be linked to sexual contact.
• Sexually active individuals, including gay, bisexual, and other men who have sex with men, who develop severe, persistent diarrhoea, or diarrhoea with blood, should get tested for shigellosis.
• Individuals diagnosed with shigellosis should avoid all sexual activity for seven days after symptoms are fully resolved and avoid oral–anal contact for up to six weeks due to prolonged bacterial shedding [5].
• Avoid faecal-oral exposure during sexual activity through proper hygiene measures (i.e. use gloves for fingering/fisting, dental dams for oral–anal contact, change condoms between oral and anal sex, avoid sharing sex toys, and clean them thoroughly between uses).
   

For healthcare professionals

• Consider sexually transmitted Shigella in adult males with gastroenteritis.
• Take a sexual history when clinically appropriate.
• Ensure antimicrobial susceptibility testing for Shigella isolates.
• Report cases to national public health authorities and submit isolates to reference laboratories.
• Recognise that prophylactic or frequent antibiotic use for other STIs may contribute to resistance patterns in Shigella.
• Consider testing for other STIs in accordance with testing guidelines and clinical indication.

For public health authorities

• Increase awareness among clinicians, laboratories and sexual health services about MDR/XDR Shigella circulation.
• Support enhanced microbiological surveillance and cluster investigation.
• Promote communication strategies that address low awareness of sexually transmissible shigellosis, particularly among gay, bisexual, and other men who have sex with men.
• Collaborate with civil society organisations that work with gay, bisexual, and other men who have sex with men to ensure that messaging uses appropriate language and can be delivered through trusted channels. 
• Reinforce guidance on culture, susceptibility testing and reporting to ensure early detection of resistance and treatment failures.
• Countries are encouraged to report clusters, including sequences, of MDR and XDR Shigella cases to EpiPulse.

References

1. US Centers for Disease Control and Prevention (CDC). Logan N, Birhane MG, McDonald SL, et al. Emergence of Extensively Drug-Resistant Shigellosis — United States, 2011–2023. MMWR Morb Mortal Wkly Rep 2026;75:173–178. Available at: https://www.cdc.gov/mmwr/volumes/75/wr/mm7513a1.htm?s_cid=mm7513a1_w
2. European Centre for Disease Prevention and Control (ECDC). Rapid risk assessment (RRA): Increase in extensively-drug resistant Shigella sonnei infections in men who have sex with men in the EU/EEA and the UK. ECDC: Stockholm; 2022. Available at: https://www.ecdc.europa.eu/en/publications-data/rapid-risk-assessment-i…
3. European Centre for Disease Prevention and Control (ECDC). Epidemiological Update: Spread of multidrug-resistant Shigella in EU/EEA among gay, bisexual and other men who have sex with men. ECDC: Stockholm; 2023. Available at: https://www.ecdc.europa.eu/en/news-events/spread-multidrug-resistant-sh…
4. de Vries HJC, Nori AV, Kiellberg Larsen H, et al. 2021 European Guideline on the management of proctitis, proctocolitis and enteritis caused by sexually transmissible pathogens. J Eur Acad Dermatol Venereol. 2021;35(7):1434-1443. Available at: https://iusti.org/wp-content/uploads/2021/07/European-guideline-on-the-…
5. Richardson D, Pakianathan M, Ewens M, et al. British Association of Sexual Health and HIV (BASHH) United Kingdom national guideline for the management of sexually transmitted enteric infections 2023. Int J STD AIDS. 2023;34(9):588-602. Available at: https://www.bashh.org/_userfiles/pages/files/resources/bashhentericguid…
6. Baker K, Dallman T, Ashton P et al. Intercontinental dissemination of azithromycin-resistant shigellosis through sexual transmission: a cross-sectional study. The Lancet Infectious Diseases, 2015; 15, 913-921. Available at: https://www.thelancet.com/journals/laninf/article/PIIS1473-3099(15)0000…
7. European Centre for Disease Prevention and Control (ECDC). Cases of Shigella infections in five EU countries related to the Darklands festival in Belgium, with strains resistant to many commonly used antimicrobial agents. Weekly Communicable Disease Threats Report. Week 15, 7–13 April 2024. Available at: https://www.ecdc.europa.eu/sites/default/files/documents/Communicable-d….