Typhoid Fever Definition
Typhoid fever is a systemic bacteremic illness caused by Salmonella enterica subspecies enterica serovar Typhi (S. typhi), characterized by fever, headache, lethargy, malaise, and abdominal pain, followed by hepatosplenomegaly and stupor, with diarrhea being an uncommon feature despite the gastrointestinal portal of entry. 1
Causative Organism and Transmission
Typhoid fever is caused specifically by Salmonella typhi, a human-specific Gram-negative pathogen transmitted via the fecal-oral route through contaminated food or water. 2, 3
Paratyphoid fever, a clinically similar but typically milder illness, is caused by Salmonella Paratyphi A and B, and together with typhoid fever these are collectively termed "enteric fever." 1
The organism is exceptionally host-specific to humans and demonstrates remarkable ability to evade innate immune detection, leading to systemic dissemination throughout the body. 4
Clinical Presentation
The hallmark presentation is sustained fever that may be accompanied by headache, lethargy, malaise, and abdominal pain, progressing to hepatosplenomegaly and altered mental status (stupor). 1
Importantly, while the portal of entry is the gastrointestinal tract, diarrhea is NOT a common feature of typhoid fever, distinguishing it from other Salmonella infections. 1
In severe cases, typhoid can progress to life-threatening complications including acute liver failure, though this is rare. 5
Left untreated, typhoid fever can follow a severe and potentially lethal course. 2
Epidemiology and Risk Factors
Typhoid fever incidence is highest in South and Southeast Asia, with moderate risk in Central and South America, Africa, Central and East Asia, and Oceania. 1
In the United States, typhoid fever is rare with approximately 441 cases reported annually during 1985-1994, and 68% of patients with S. typhi reported international travel in the 30 days before symptom onset. 1
Enteric fever should be suspected in any febrile person (with or without diarrhea) who has traveled to endemic areas, consumed foods prepared by individuals with recent endemic exposure, or had laboratory exposure to S. typhi. 1
Approximately 5% of infected individuals become chronic asymptomatic carriers, with the gallbladder serving as a harbor for the organism, and these carriers contribute to ongoing transmission through biofilm formation. 4
Carrier State and Chronic Infection
During illness, S. typhi can establish residence in the gallbladder, leading to chronic carriage that may persist for extended periods. 4
Chronic carriers continuously shed organisms and pose a transmission risk, with outbreaks in the United States typically associated with foodborne transmission from asymptomatic carriers. 1
The organism's ability to form biofilms facilitates both pathogenicity and persistence within the human body, contributing to the chronic carrier state. 4
Common Pitfalls in Recognition
Typhoid fever may be difficult to distinguish from other febrile conditions in returned travelers, requiring a high index of suspicion based on travel history. 1
The absence of diarrhea should not exclude typhoid fever from the differential diagnosis, as this is actually typical for the disease. 1
Clinicians must recognize that typhoid is a bacteremic systemic illness rather than primarily a gastrointestinal infection, despite its enteric portal of entry. 1