A deadly illness once consigned to the annals of ancient history is staging a formidable comeback, mutating to resist even the most potent modern pharmaceuticals. Typhoid fever, caused by the Salmonella enterica serotype Typhi (S. Typhi) bacterium, predominantly affects regions in Africa, Asia, and Latin America. Globally, approximately 9.2 million cases are reported annually, with a mere 5,700 occurring in the United States, largely contracted during international travel.
Rising Threat of Antibiotic Resistance
In the US, typhoid fever results in around 620 hospitalizations each year, though fatalities are exceedingly rare, with fewer than one death reported annually. Without treatment, the fever proves fatal in 10 to 20 percent of cases. The standard care involves antibiotics, but recent research highlights a troubling evolution: the bacterium is mutating to evade conventional treatments, with rarer antibiotic-resistant strains now supplanting those responsive to oral medications.
Genomic Study Reveals Alarming Trends
In 2022, an international team of scientists sequenced the genomes of 3,489 S. Typhi strains collected from 2014 to 2019 in Nepal, Bangladesh, Pakistan, and India. Their findings documented a significant increase in the extensively drug-resistant (XDR) Typhi strain. This strain not only resists older medications like ampicillin, chloramphenicol, and trimethoprim/sulfamethoxazole but also newer, more powerful drugs such as fluoroquinolones and third-generation cephalosporins.
Researchers expressed deep concern over both the rise of this strain and its accelerated global dissemination, including to North America and Europe. While most XDR Typhi strains originate in South Asian nations, the study identified 200 cases of international spread since 1990, primarily to East and Southern Africa, but now extending to Canada, the United Kingdom, and the United States.
Expert Warnings and Global Implications
Jason Andrews, an infectious disease researcher at Stanford University and lead author of the study, emphasized the urgency of the situation. He stated, 'The rapid emergence and spread of highly-resistant strains of S. Typhi in recent years is a genuine cause for alarm, necessitating the urgent expansion of prevention measures, especially in high-risk countries. Moreover, the repeated international spread of resistant strains underscores that typhoid control and antibiotic resistance must be addressed as global, not merely local, challenges.'
Historical Context and Current Dominance
XDR Typhi first gained scientific attention when identified in Pakistan in 2016, and within just three years, it became the dominant strain in that country. Historically, typhoid was treated with antimicrobials, but by the early 2000s, mutations resistant to these drugs accounted for over 85 percent of cases in Bangladesh, India, Pakistan, Nepal, and Singapore. Today, only one medication remains effective against it, but researchers fear imminent mutations could render this last line of defense obsolete.
The study authors warned that the proliferation of drug-resistant strains 'threatens the efficacy of all oral antimicrobials for typhoid treatment,' posing a severe public health risk.
Transmission and Symptoms
The bacteria responsible for typhoid fever are shed in human stool, spreading when individuals come into contact with contaminated food, water, or surfaces. Transmission can also occur through direct contact with items soiled by an infected person's stool. Symptoms encompass a persistent high fever lasting more than three days, weakness, abdominal pain, constipation or diarrhea, cough, loss of appetite, and, in some instances, a distinctive rash with rose-colored spots.
Early treatment is critical, as untreated typhoid can lead to lasting health complications or death. With antibiotic resistance on the rise, bacteria can proliferate unchecked, resulting in illnesses that are harder to treat, more prolonged, and more severe.
Prevention and Recommendations
To combat typhoid fever, the Centers for Disease Control and Prevention (CDC) advises vaccination before traveling to endemic regions. Two vaccine options are available: an oral version consisting of four pills taken over four days for individuals aged six and older, and an injectable single-shot for those two and older. Both should be administered at least two weeks prior to travel.
While abroad, the CDC recommends adhering to safe dietary practices, such as avoiding raw foods and street vendors, ensuring food is thoroughly cooked, consuming pasteurized milk, and maintaining rigorous hygiene, including thorough handwashing. These measures are essential to curbing the spread of this resurgent, drug-resistant threat.
