Enteric Fever

Enteric fever is a systemic febrile illness caused by the human-restricted bacteria Salmonella enterica serovar Typhi (typhoid fever) and serovars Paratyphi A, B, and C (paratyphoid fever). Acquired through food or water contaminated with human faeces, it is an important cause of fever in travelers returning from regions where the organisms are endemic.

Definition

Enteric fever denotes the clinical syndrome of typhoid and paratyphoid fever: a systemic infection by Salmonella enterica serovars Typhi or Paratyphi, transmitted by the faecal-oral route and characterized by sustained fever and bacteraemia rather than primarily by diarrhea.

Scope

This entry covers the definition of enteric fever, its causative serovars, transmission, clinical pattern, and the public-health significance of antimicrobial resistance, framed for travelers and returned-traveler differential diagnosis. It is a reference overview describing the disease and its evidence base, not individualized clinical or prescribing advice.

Core questions

• How does enteric fever differ from non-typhoidal Salmonella and from secretory traveler's diarrhea?
• Which serovars cause typhoid versus paratyphoid fever, and how are they transmitted?
• Why is rising antimicrobial resistance central to the current significance of the disease?

Key concepts

• Salmonella enterica serovar Typhi
• Salmonella Paratyphi A, B, C
• Faecal-oral transmission
• Systemic bacteraemic illness
• Sustained fever
• Chronic carriage
• Antimicrobial resistance

Mechanisms

After ingestion in contaminated food or water, Salmonella Typhi and Paratyphi cross the intestinal epithelium and are taken up by mononuclear phagocytes, producing a systemic bacteraemic illness rather than the secretory diarrhea typical of many enteric infections. The result is a sustained febrile illness; a minority of people become chronic carriers who shed the organism long-term, sustaining transmission. The human-restricted nature of these serovars underlies their faecal-oral, person-associated epidemiology.

Clinical relevance

Enteric fever is a leading cause of systemic febrile illness in travelers returning from endemic areas and is an important consideration in the evaluation of fever after travel. Understanding it supports recognition of a bacteraemic, non-diarrheal pattern distinct from traveler's diarrhea; the entry describes disease patterns and the resistance problem rather than recommending specific antimicrobial regimens for an individual.

Epidemiology

Typhoid and paratyphoid fever remain concentrated in regions with limited access to safe water and sanitation, particularly parts of South and Southeast Asia and sub-Saharan Africa, and feature among imported febrile illnesses in returned-traveler surveillance. Escalating antimicrobial resistance, including multidrug-resistant and fluoroquinolone-non-susceptible strains, is a defining contemporary feature summarized in invasive-Salmonella reviews.

Evidence & guidelines

Comprehensive reviews such as Crump and colleagues (2015) synthesize the epidemiology, diagnosis, and resistance landscape of invasive Salmonella infections; returned-traveler surveillance contextualizes enteric fever among imported fevers. These sources describe diagnostic and management evidence and resistance trends at a population and reference level rather than prescribing treatment.

History

Typhoid fever was distinguished from typhus and characterized clinically and pathologically in the nineteenth century, and the causative bacillus was later identified as Salmonella Typhi. Through the twentieth century, sanitation, vaccines, and antibiotics transformed its course in higher-income settings, while it persisted where water and sanitation infrastructure remained limited; the more recent emergence of multidrug-resistant and extensively drug-resistant strains has renewed its prominence as a global-health and travel-medicine concern.

Debates

How should rising antimicrobial resistance reshape diagnosis and control?

The spread of multidrug-resistant and fluoroquinolone-non-susceptible, and more recently extensively drug-resistant, strains has intensified debate over empirical management, vaccination strategy, and surveillance priorities for enteric fever.

Key figures

• John A. Crump
• Christopher M. Parry
• Melita A. Gordon

Seminal works

• crump-2015
• freedman-2006

Frequently asked questions

What is the difference between typhoid and paratyphoid fever?

Both are forms of enteric fever; typhoid fever is caused by Salmonella enterica serovar Typhi and paratyphoid fever by serovars Paratyphi A, B, or C. They produce a similar systemic febrile illness and are grouped together as enteric fever.

Why is enteric fever different from ordinary traveler's diarrhea?

Enteric fever is a systemic, bacteraemic illness dominated by sustained fever rather than the acute secretory or inflammatory diarrhea that defines most traveler's diarrhea, and it is caused specifically by the typhoidal Salmonella serovars.