Rapid risk assessment: Increase in extensively-drug resistant Shigella sonnei infections in men who have sex with men in the EU/EEA and the UK
On 27 January 2022, the United Kingdom Health Security Agency (UKHSA) reported an increase in extensively-drug resistant Shigella sonnei infections. Since then, Austria, Belgium, Denmark, France, Germany, Ireland, Italy, Norway, and Spain have reported cases of shigellosis with sampling dates from 2020 to 2022 and with isolates either closely genetically related by whole genome sequencing (WGS), or with the same or a very similar resistance profile. Most cases were in adult men who have sex with men (MSM). A large proportion of the patients with available information were reported to be infected through sexual transmission.
This document assesses the risk of further spread of S. sonnei amongst MSM and in the broader population in EU/EEA countries, resulting from the current increase in extensively-drug resistant S. sonnei infections.
Sexual contact networks among some MSM in Europe are highly interconnected, sometimes involving high-risk sexual practices often involving anonymous sexual contacts. The probability of new infections in MSM exposed to high-risk sexual practices, and the spread in EU/EEA countries in the coming months is assessed as high, as outbreaks among MSM usually occur over long time periods. If the lifting of restrictions related to the COVID-19 pandemic is also considered, travel and the number of social events will likely increase as well. The impact of such infections is assessed as low in most instances as S. sonnei is generally associated with mild disease in healthy adults. However, the impact of the infection could be more severe in immunocompromised adults. In addition, the resistance profile of this strain limits treatment options, whether this is aimed at shortening shedding in mild cases or treating severe cases. Based on these levels of probability and impact, the level of risk for MSM is assessed as moderate.
Opportunities for infection in the non-MSM population increase when transmission among MSM is high. Currently, there have been very few reports of non-MSM cases associated with the ongoing increase of cases of extensively-drug resistant S. sonnei. The probability of infections in the broader population, including the probability of foodborne outbreaks associated with infected food handlers, is assessed as very low. The impact of such infections is assessed as low in most instances, due to a generally mild disease in healthy individuals. Consequently, the level of risk for the broader population is assessed as low.
Options for response
Men who have sex with men should aim to minimise the risk of infection through faecal-oral exposure during sexual activity by practicing safe sex and good hygiene. MSM presenting symptoms of gastrointestinal illness are recommended to get tested for gastrointestinal pathogens and other STIs and to inform the treating physician about the infection risk through sexual activity. Sexual activity should be avoided for at least seven days after symptoms have stopped and faecal-oral contact during sex should be avoided for four to six weeks. Awareness activities targeted at MSM, especially those identified to be at higher risk, e.g. MSM on pre-exposure prophylaxis (PrEP), should also be considered to increase knowledge about the ongoing threat of shigellosis.
People with gastrointestinal symptoms should not handle and prepare food for catering or in private households until fully recovered or stool culture is negative for Shigella. In healthcare settings, in addition to standard precautions, contact precautions, including placement in a single room with a dedicated toilet, adequate access to hand hygiene and regular environmental cleaning, should be considered for suspected or confirmed extensively drug-resistant S. sonnei cases.
There are very limited options for treatment of extensively-drug resistant S. sonnei. Clinicians should be aware of increasing trends of antimicrobial resistance in Shigella spp. and ensure susceptibility testing on all clinical isolates, especially from high-risk groups, from patients returning from international destinations, and from MSM, who are at risk of a resistant infection. When antimicrobial treatment is indicated, it should be based on the results of susceptibility testing. Non-specialist physicians should be aware that among young adult males, especially among those with no travel history, the route of acquisition can be sexual. Timely antimicrobial resistance profiles with sufficient epidemiological information will enable early detection and investigation of treatment failures and will inform national and international treatment guidelines. Reporting of outbreaks with extensively-drug resistant S. sonnei and related treatment failures should be strengthened at the national and European level to enable rapid intervention and to prevent the spread of antimicrobial-resistant S. sonnei.
Timely sharing of data on treatment failure among EU/EEA countries will facilitate a more effective response. The use of EpiPulse is encouraged to implement rapid information sharing at the European level. Any new information linked to this event can be reported in EpiPulse.
ECDC encourages countries to perform whole genome sequencing (WGS) on S. sonnei isolates linked to human infections, especially extensively drug-resistant ones. ECDC can provide WGS support for isolates possibly linked to multi-country events.