The Centers for Disease Control and Prevention (CDC) recently published findings in the Morbidity and Mortality Weekly Report highlighting this trend. Analysis of nearly 17,000 Shigella isolates showed that the proportion of extensively drug-resistant (XDR) cases rose from 0% during the 2011–2015 period to 8.5% in 2023. While most shigellosis cases resolve without specific treatment, antibiotics are indicated for severe illness or to reduce transmission in high-risk settings. The rise in XDR strains means that these standard interventions may no longer be effective for a growing subset of patients, who are experiencing more severe outcomes. In fact, more than one-third of patients with XDR shigellosis required hospitalization.
Clinicians on the front lines are observing this acceleration firsthand. Shangxin Yang, PhD, who directs the Molecular Microbiology and Pathogen Genomics Laboratory at UCLA Health, noted that while the hospital identified only one local case of XDR Shigella in 2022, the facility has since seen roughly one case per month. Yang described the situation as “an explosion of this pathogen in the community.” Similarly, Ferric Fang, MD, and colleagues in the Seattle area have noted that while the CDC estimates 450,000 Americans contract shigellosis annually and most recover with fluids and rest, the severity of cases among specific populations is escalating.
This phenomenon is not isolated to the United States. A study from the University of Cambridge, published in July, utilized DNA sequencing techniques previously deployed to track COVID-19 variants to analyze bacterial strains in the United Kingdom. The research, which cited data from the UK Health Security Agency, identified more than 2,500 cases of Shigella last year that were potentially acquired through sexual contact. The study found that sexually transmissible strains spread much faster and develop drug resistance more quickly than non-sexually transmitted variants. Approximately 70% of the sexually transmitted strains evaluated in the study were resistant to at least one relevant antibiotic.
The epidemiological shift is driven by changes in how the bacteria are transmitted. Previously, outbreaks in the U.S. involved drug-susceptible strains and primarily affected children. Now, national surveillance data indicates that most XDR cases occur among adult men, often within men who have sex with men (MSM) communities. The rapid transmission of these strains through sexual contact creates a favorable environment for the selection of resistant bacteria, particularly when antibiotics are used frequently. Naeemah Logan, MD, an epidemiologist with the CDC’s National Center for Emerging and Zoonotic Infectious Diseases and a co-author of the CDC report, described the findings as “a very concerning pattern of XDR Shigella strains that are being seen among vulnerable populations.”
The clinical implications are significant. Shigella causes severe gastrointestinal symptoms, including diarrhea, vomiting, fever, and stomach pain, and can lead to dysentery. For the majority of the population, the infection may clear up on its own. However, for those with compromised immune systems, such as individuals living with HIV, or those infected with XDR strains, the lack of effective treatment options poses a serious risk. The CDC report emphasized that while most infections do not require antimicrobial agents, the inability to treat severe cases effectively with current antibiotics represents a critical gap in care.
Health authorities are now focused on monitoring these resistant strains and developing guidelines for their management. The next verified development will likely involve updated treatment protocols and increased genomic surveillance to track the evolution of these bacteria in real-time. As the distinction between a childhood ailment and a sexually transmitted, drug-resistant infection blurs, the medical community is preparing for a new era of managing Shigella, one that requires a nuanced understanding of both transmission dynamics and antimicrobial resistance.
