For millennia, typhoid fever has been a global health threat, but the disease is now evolving at an alarming rate, developing resistance to multiple antibiotics. While often considered a concern of the developing world, the increasing prevalence of drug-resistant strains poses a growing risk internationally. New research reveals that Salmonella enterica serovar Typhi (S. Typhi), the bacterium responsible for typhoid fever, is rapidly replacing strains susceptible to treatment, threatening to render current therapies ineffective.
Antibiotics remain the primary defense against typhoid fever, but their efficacy is dwindling. Over the past three decades, S. Typhi has demonstrated a growing resistance to oral antibiotics, a trend that is now accelerating. A recent study, published in The Lancet Microbe in 2022, sequenced the genomes of nearly 3,500 S. Typhi strains collected between 2014 and 2019 from Nepal, Bangladesh, Pakistan and India, revealing a surge in extensively drug-resistant (XDR) Typhi.
XDR Typhi isn’t simply resistant to older antibiotics like ampicillin, chloramphenicol, and trimethoprim/sulfamethoxazole; it’s also showing increasing resistance to newer drugs, including fluoroquinolones and third-generation cephalosporins. This escalating resistance is driving a global spread, with nearly 200 instances of international transmission identified since 1990, according to the research. The majority of these exported strains have reached Southeast Asia, East and Southern Africa, but cases have also been detected in the United Kingdom, the United States, and Canada.
“The speed at which highly resistant strains of S. Typhi have emerged and spread in recent years is a real cause for concern, and highlights the need to urgently expand prevention measures, particularly in countries at greatest risk,” said Stanford University infectious disease researcher Jason Andrews, as reported upon the study’s publication.
Scientists have been sounding the alarm about drug-resistant typhoid for years. The first XDR typhoid strain was identified in Pakistan in 2016, and by 2019, it had become the dominant genotype within the nation. Historically, third-generation antimicrobials like quinolones and cephalosporins were used to treat these infections, but resistance to these drugs has been steadily increasing since the early 2000s, particularly in Bangladesh, India, Pakistan, Nepal, and Singapore. By that time, mutations conferring resistance to quinolones accounted for over 85% of cases in those regions, with cephalosporin resistance also on the rise.
Currently, azithromycin, a macrolide antibiotic, is often the last remaining oral treatment option. However, the 2022 study revealed that mutations conferring resistance to azithromycin are now spreading, potentially jeopardizing the effectiveness of all oral antimicrobials used to treat typhoid. While these mutations haven’t yet been incorporated into XDR S. Typhi strains, their emergence represents a critical threat.
Typhoid fever remains a significant public health concern. Without treatment, up to 20% of cases can be fatal, and in 2024, over 13 million cases of typhoid were reported globally. The Centers for Disease Control and Prevention (CDC) highlights the importance of vaccination as a preventative measure, noting that typhoid conjugate vaccines are increasingly available.
The authors of the Lancet Microbe study emphasize the urgent need to expand prevention efforts, particularly through the use of typhoid conjugate vaccines in endemic countries. “Such measures are needed in countries where antimicrobial resistance prevalence among S. Typhi isolates is currently high, but given the propensity for international spread, should not be restricted to such settings,” they wrote.
South Asia remains the epicenter of typhoid fever, accounting for approximately 70% of all cases worldwide. However, the COVID-19 pandemic underscored the ease with which disease variants can spread in our interconnected world. Expanding access to typhoid vaccines and investing in research for new antibiotics are crucial steps in preventing a wider crisis.
A 2021 study conducted in India estimated that vaccinating children against typhoid in urban areas could prevent up to 36% of cases and deaths. Pakistan has taken a leading role in prevention, becoming the first nation globally to offer routine typhoid immunization, with several other countries now following suit or considering similar programs. As of April 2025, the World Health Organization has prequalified four typhoid conjugate vaccines for use in childhood immunization programs in endemic regions, according to the CDC.
Antibiotic resistance is a leading cause of death worldwide, surpassing fatalities from HIV/AIDS and malaria. Vaccines, where available, represent one of the most effective tools for preventing future outbreaks.
The emergence of XDR and azithromycin-resistant S. Typhi demands immediate action. Continued surveillance, expanded vaccination programs, and renewed investment in antibiotic research are essential to combat this growing threat and protect global public health.
Disclaimer: This information is intended for general knowledge and informational purposes only, and does not constitute medical advice. It is essential to consult with a qualified healthcare professional for any health concerns or before making any decisions related to your health or treatment.
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