Typhoid fever: Good news, not-so-good news, and what it means for travellers

Author(s):  Dr Sherilyn Houle

Typhoid fever is a bacterial illness transmitted through contaminated food or water. While it is endemic in parts of Latin America, Africa, and Asia, the greatest risk for infection is in South Asia.

A recent study¹ using the Global Burden of Disease database estimated the global incidence rate of typhoid at 98.6 cases per 100,000 population in 2021, representing a decrease of over 69% since 1990.  Overall, incidence and disability rates saw the greatest decreases in countries with lower socio-demographic index scores, likely impacted by improved water and sanitation services and the introduction of immunization programs in high-risk areas.

But the news isn’t all good. While the incidence of typhoid is decreasing, extensively drug-resistant (XDR) typhoid, with resistance to ampicillin, ceftriaxone, ciprofloxacin, and trimethoprim-sulfamethoxazole, is a concern. Among 17 cases of culture-confirmed XDR S. typhi identified at GeoSentinel sites (68 specialized travel and tropical medicine clinics from 28 countries),² all had travelled to Pakistan to visit friends or relatives and only one was known to be vaccinated. Isolates were susceptible to meropenem and azithromycin. The authors advise that suspected cases of enteric fever among recent travellers to Pakistan should therefore be treated empirically with a carbapenem or azithromycin. Ongoing monitoring of antimicrobial susceptibility will be important as the spread of XDR S. typhi is expected.

Offering vaccination to travellers to highly endemic areas remains an important preventive strategy. While polysaccharide and oral live attenuated vaccines are used among travellers, they are only indicated among those ≥ 2 years and ≥ 5 years, respectively. Newer vaccines conjugated to tetanus toxoid protein are indicated among those ≥ 6 months but are currently only used for routine immunization in Pakistan, Liberia, Zimbabwe, Samoa, Nepal, and Malawi.³ A phase 3 randomized controlled trial among children aged 9 months to 12 years in Malawi reported vaccine efficacy of 78.3% overall across 4 years of follow-up, declining by only 1.3% per year following a single dose.³ The impact of vaccination campaigns in endemic areas on illness among travellers is yet to be determined.

Among 1,651 travel consultations performed at a travel clinic in the U.K., typhoid vaccine was the second-most recommended vaccine and the fourth-most accepted (following yellow fever, cholera, and meningococcal ACWY), with declining acceptance rates as the number of recommended vaccines increases.⁴ Typhoid vaccination should continue to be encouraged to travellers visiting areas of high endemicity, with counselling to travellers to Pakistan about extensive drug-resistant typhoid in the region and the importance of prevention.

Dr. Sherilyn HOULE

References:

1. Chen W, Chen Y, Cheng Z, et al. Global patterns of syphilis, gonococcal infection, typhoid fever, paratyphoid fever, diphtheria, pertussis, tetanus, and leprosy from 1990 to 2021: findings from the Global Burden of Disease Study 202  Infectious Diseases of Poverty 2024;13:66. doi: 10.1186/s40249-024-01231-2

2. Posen HJ, Wong W, Farrar DS, et al. Travel-associated extensively drug-resistant typhoid fever: a case series to inform management in non-endemic regions. Journal of Travel Medicine 2023;30(1):taac086. doi: 10.1093/jtm/taac086

3. Patel PD, Liang Y, Meiring JE, et al. Efficacy of typhoid conjugate vaccine: final analysis of a 4-year phase 3, randomised controlled trial in Malawian children. Lancet 2024;403(10425):459-468. doi: 10.1016/S0140-6736(23)02031-7

4. Harrison T, Clark J, Darton TC, et al. Less is more: Uptake of recommended vaccines in a UK travel clinic. Journal of Infection 2024;88(3):106109. doi: 10.1016/j.jinf.20201.008

References

[1].  Global patterns of syphilis, gonococcal infection, typhoid fever, paratyphoid fever, diphtheria, pertussis, tetanus, and leprosy from 1990 to 2021: findings from the Global Burden of Disease Study 2021.  Chen W, Chen Y, Cheng Z, et al. ‐ Infectious Diseases of Poverty 2024;13:66. [link]
[2].  Travel-associated extensively drug-resistant typhoid fever: a case series to inform management in non-endemic regions.  Posen HJ, Wong W, Farrar DS, et al. ‐ Journal of Travel Medicine 2023;30(1):taac086. [link]
[3].  Efficacy of typhoid conjugate vaccine: final analysis of a 4-year phase 3, randomised controlled trial in Malawian children.  Patel PD, Liang Y, Meiring JE, et al. ‐ Lancet 2024;403(10425):459-468. [link]
[4].  Less is more: Uptake of recommended vaccines in a UK travel clinic.  Harrison T, Clark J, Darton TC, et al. ‐ Journal of Infection 2024;88(3):106109. [link]