Typhoid fever
Typhoid fever is a prolonged systemic infection caused by Salmonella enterica serotype Typhi, marked by stepwise fever, relative bradycardia, and rose spots. Diagnosis rests on blood or bone marrow culture, and first-line treatment is ceftriaxone for severe or resistant disease or azithromycin for uncomplicated illness, since fluoroquinolone resistance is now widespread.
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What this article covers
- Overview
Typhoid fever is a prolonged systemic infection caused by Salmonella enterica serotype Typhi, or the related serotype Paratyphi (A, B, or C), acquired by ingesting food or water contaminated by the stool of an infected person.
- Epidemiology
Human-only reservoir: Unlike nontyphoidal Salmonella, which has a broad animal reservoir in poultry, eggs, and reptiles, Salmonella Typhi infects only humans, so transmission tracks sanitation and an active case or chronic carrier.
- Risk factors
Travel to or residence in an endemic region: The Indian subcontinent, Southeast Asia, and sub-Saharan Africa without prior vaccination is the dominant risk factor for travel-associated cases.
- Pathophysiology
Entry through Peyer patches: The organism invades via M cells overlying ileal Peyer patches, is engulfed by mononuclear phagocytes, and survives intracellularly rather than being cleared, unlike most enteric pathogens.
- Clinical features
Incubation: Fever with headache, malaise, myalgia, pharyngitis, and anorexia follows ingestion by 1 to 2 weeks.
- Differential diagnosis
Malaria: Shares fever and travel history, but the fever is classically paroxysmal (every 48 or 72 hours depending on species) with rigors, and intraerythrocytic parasites are visible on a blood smear, without a salmon-colored rash.
- Diagnosis
Isolation of Salmonella Typhi or Paratyphi from blood, bone marrow, stool, or urine culture establishes the diagnosis; blood culture is the standard first test, most sensitive in the first week of…
- Management
First, start empiric antibiotic therapy as soon as typhoid fever is clinically suspected in a compatible traveler, rather than waiting for culture confirmation, since delayed treatment raises the risk of perforation and death.
- Complications
Intestinal hemorrhage or perforation: Occurs 2 to 3 weeks after onset from ulceration of the ileal Peyer patches, presenting as sudden abdominal pain, peritonitis, or a falling hematocrit; a surgical emergency.
- Prognosis
Antibiotic treatment decreases mortality and shortens the duration of fever compared with untreated infection, which can persist 4 to 8 weeks.
- Prevention
Vaccination before travel to an endemic area: the oral live-attenuated Ty21a vaccine is given as four doses on days 0, 2, 4, and 6 and is generally repeated every 5 years with continued exposure…
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