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PubMed This is a summary of 19 peer-reviewed journal articles Updated
Infectious Disease · Typhoid Fever

Understanding Typhoid Fever: Basics and Biology

At a Glance

Typhoid fever is a treatable but serious bacterial infection caused by Salmonella Typhi, spreading through contaminated food and water. Early antibiotic treatment prevents severe complications. Highly effective vaccines offer protection for travelers and people living in high-risk areas.

Typhoid fever is a serious systemic infection (an infection that affects the entire body) caused by the bacteria Salmonella Typhi [1][2]. Unlike other types of Salmonella that cause simple food poisoning, S. Typhi only lives in humans [2]. When someone swallows these bacteria, they travel from the intestines into the bloodstream and can spread to the liver, spleen, and bone marrow [3][4].

While the diagnosis can be frightening, it is important to know three stabilizing facts:

  1. It is treatable: Most cases of typhoid fever can be successfully treated with the correct course of antibiotics [5].
  2. Vaccines are available: Highly effective vaccines, especially the Typhoid Conjugate Vaccine (TCV), can prevent infection and are recommended for those in high-risk areas [6][7].
  3. Early detection works: Finding and treating the infection early prevents the most severe complications, such as internal bleeding or intestinal damage [5][8].

How Typhoid Spreads

Typhoid fever is transmitted through the fecal-oral route [1]. This means the bacteria are shed in the stool (and sometimes urine) of an infected person or a chronic carrier (someone who has no symptoms but still carries the bacteria) [9]. You can become infected by:

  • Drinking water contaminated by sewage containing the bacteria [1][10].
  • Eating food handled by someone who is shedding the bacteria and has not washed their hands thoroughly [10][11].
  • Eating raw fruits or vegetables that were fertilized with human waste or washed with contaminated water [1].

The Biology of the Infection

Once inside the body, S. Typhi uses specialized “tools” to invade the lining of the intestines [2]. It then hitches a ride inside macrophages—the very immune cells meant to kill bacteria—and uses them to travel through the body undetected [3][4].

In some people, the bacteria settle in the gallbladder, especially if gallstones are present [9]. These individuals can become long-term carriers, shedding the bacteria for months or even years without feeling sick themselves [12][13].

Who is at Risk?

Typhoid fever is a global health concern, with the highest burden found in parts of South Asia and Sub-Saharan Africa [14][15].

  • Young Children: Children, particularly those under the age of five in endemic areas, are disproportionately affected and often experience the highest rates of disease [14][16].
  • Travelers: People visiting regions where typhoid is common are at risk, especially if they are staying with friends or relatives or eating in areas with limited access to clean water [17].
  • Communities with Poor Sanitation: Lack of access to clean water, proper toilets (WASH infrastructure), and crowded housing conditions significantly increase the risk of transmission [11][10].

A Note on Drug Resistance

In recent years, some strains of typhoid have become multidrug-resistant (MDR) or extensively drug-resistant (XDR) [17][18]. This means that some common antibiotics no longer work against them [5]. Because of this, doctors may need to use specific “reserve” antibiotics or perform sensitivity testing to ensure the chosen medicine will be effective against the specific strain causing the illness [5][19].

Common questions in this guide

How does typhoid fever spread?
Typhoid fever spreads through the fecal-oral route. You can become infected by drinking contaminated water, eating raw vegetables washed in dirty water, or eating food handled by an infected person who hasn't washed their hands properly.
What is a typhoid carrier?
A chronic carrier is someone who harbors the Salmonella Typhi bacteria in their body, often in the gallbladder, but shows no symptoms of illness. They can unknowingly shed the bacteria in their stool for months or years, infecting others.
Can typhoid fever be treated?
Yes, most cases of typhoid fever can be successfully treated with antibiotics. However, finding and treating the infection early is crucial to prevent serious complications like internal bleeding or intestinal damage.
What happens if I have a drug-resistant strain of typhoid?
Some strains of the bacteria have mutated to become multidrug-resistant (MDR) or extensively drug-resistant (XDR), meaning common antibiotics no longer work. If you have a resistant strain, your doctor will need to perform specific testing to find a specialized reserve antibiotic to treat it.
Who is at the highest risk for getting typhoid fever?
Young children under five, travelers visiting areas where the disease is common, and people living in communities with poor sanitation and limited access to clean water are at the highest risk of contracting typhoid fever.

Questions to Ask Your Doctor

Curated prompts to bring to your next appointment.

  1. 1.What diagnostic test (blood, stool, or bone marrow culture) will you use to confirm the diagnosis?
  2. 2.Are there known cases of drug-resistant (MDR or XDR) typhoid in the region where I (or my child) may have been exposed?
  3. 3.Based on the local resistance patterns, which antibiotic do you recommend starting with?
  4. 4.If symptoms don't improve within 3-5 days of starting treatment, what is the next step?
  5. 5.What signs of complications, such as internal bleeding or intestinal issues, should I watch for at home?

Questions For You

Tap a prompt to share your answer — we'll use it plus this page's context to start a tailored conversation.

References

References (19)
  1. 1

    Household and Environmental Typhoid Fever Transmission in Bandar Lampung City, Indonesia: A Case-Control Study.

    Yushananta P, Putri MFE

    JNMA; journal of the Nepal Medical Association 2024; (62(277)):564-569 doi:10.31729/jnma.8744.

    PMID: 40655045
  2. 2

    Salmonella enterica serovar Typhi uses two type 3 secretion systems to replicate in human macrophages and colonize humanized mice.

    Hamblin M, Schade R, Narasimhan R, Monack DM

    mBio 2023; (14(4)):e0113723 doi:10.1128/mbio.01137-23.

    PMID: 37341487
  3. 3

    Salmonella enterica serovar Typhi uses two type 3 secretion systems to replicate in human macrophages and to colonize humanized mice.

    Hamblin M, Schade R, Narasimhan R, Monack DM

    bioRxiv : the preprint server for biology 2023; doi:10.1101/2023.06.06.543980.

    PMID: 37333307
  4. 4

    Macrophage Cell Lines and Murine Infection by Salmonella enterica Serovar Typhi L-Form Bacteria.

    Ganguli D, Chakraborty S, Chakraborty S, et al.

    Infection and immunity 2022; (90(6)):e0011922 doi:10.1128/iai.00119-22.

    PMID: 35587200
  5. 5

    Case of Carbapenem-Resistant Salmonella Typhi Infection, Pakistan, 2022.

    Nizamuddin S, Khan EA, Chattaway MA, Godbole G

    Emerging infectious diseases 2023; (29(11)):2395-2397 doi:10.3201/eid2911.230499.

    PMID: 37877663
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    Efficacy of typhoid conjugate vaccine in Nepal: final results of a phase 3, randomised, controlled trial.

    Shakya M, Voysey M, Theiss-Nyland K, et al.

    The Lancet. Global health 2021; (9(11)):e1561-e1568 doi:10.1016/S2214-109X(21)00346-6.

    PMID: 34678198
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    Genotypic Diversity among Salmonella Typhi Isolated from Children Living in Informal Settlements in Nairobi, Kenya.

    Kavai SM, Oyugi J, Mbae C, et al.

    International journal of clinical microbiology 2024; (1(3)):18-27 doi:10.14302/issn.2690-4721.ijcm-24-5195.

    PMID: 39483419
  8. 8

    Whole genome sequence analysis of Salmonella Typhi in Papua New Guinea reveals an established population of genotype 2.1.7 sensitive to antimicrobials.

    Dyson ZA, Malau E, Horwood PF, et al.

    PLoS neglected tropical diseases 2022; (16(3)):e0010306 doi:10.1371/journal.pntd.0010306.

    PMID: 35344544
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    Multiple introductions of multidrug-resistant typhoid associated with acute infection and asymptomatic carriage, Kenya.

    Kariuki S, Dyson ZA, Mbae C, et al.

    eLife 2021; (10()).

    PMID: 34515028
  10. 10

    Domestic River Water Use and Risk of Typhoid Fever: Results From a Case-control Study in Blantyre, Malawi.

    Gauld JS, Olgemoeller F, Nkhata R, et al.

    Clinical infectious diseases : an official publication of the Infectious Diseases Society of America 2020; (70(7)):1278-1284 doi:10.1093/cid/ciz405.

    PMID: 31144715
  11. 11

    Environmental Transmission of Typhoid Fever in an Urban Slum.

    Akullian A, Ng'eno E, Matheson AI, et al.

    PLoS neglected tropical diseases 2015; (9(12)):e0004212 doi:10.1371/journal.pntd.0004212.

    PMID: 26633656
  12. 12

    Siblings with typhoid fever: An investigation of intrafamilial transmission, clonality, and antibiotic susceptibility.

    Meyer Sauteur PM, Stevens MJA, Paioni P, et al.

    Travel medicine and infectious disease 2020; (34()):101498 doi:10.1016/j.tmaid.2019.101498.

    PMID: 31580900
  13. 13

    Gallbladder carriage generates genetic variation and genome degradation in Salmonella Typhi.

    Thanh Duy P, Thieu NTV, Nguyen Thi Nguyen T, et al.

    PLoS pathogens 2020; (16(10)):e1008998 doi:10.1371/journal.ppat.1008998.

    PMID: 33085725
  14. 14

    Determining the Best Immunization Strategy for Protecting African Children Against Invasive Salmonella Disease.

    Jeon HJ, Pak GD, Im J, et al.

    Clinical infectious diseases : an official publication of the Infectious Diseases Society of America 2018; (67(12)):1824-1830 doi:10.1093/cid/ciy386.

    PMID: 29746615
  15. 15

    Clinical Spectrum and Outcomes of Typhoid Fever: A Retrospective Study.

    Shafqat Z, Kanwal S, Yousaf A, et al.

    Cureus 2025; (17(10)):e94621 doi:10.7759/cureus.94621.

    PMID: 41246786
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    Estimating the incidence of enteric fever in children in India: a multi-site, active fever surveillance of pediatric cohorts.

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    BMC public health 2018; (18(1)):594 doi:10.1186/s12889-018-5498-2.

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    Five Years of GenoTyphi: Updates to the Global Salmonella Typhi Genotyping Framework.

    Dyson ZA, Holt KE

    The Journal of infectious diseases 2021; (224(12 Suppl 2)):S775-S780 doi:10.1093/infdis/jiab414.

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  18. 18

    Laboratory characterisation of Salmonella enterica serotype Typhi isolates from Zimbabwe, 2009-2017.

    Mashe T, Gudza-Mugabe M, Tarupiwa A, et al.

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  19. 19

    A review of clinical profile, complications and antibiotic susceptibility pattern of extensively drug-resistant (XDR) Salmonella Typhi isolates in children in Karachi.

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This page provides basic educational information about typhoid fever and its biology. Always consult a healthcare provider or travel medicine specialist for medical advice, vaccination recommendations, or treatment options.

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