Typhoid fever is a systemic illness caused by the bacterium Salmonella enterica subspecies enterica serovar Typhi. It is acquired through ingestion of food or water contaminated with human fecal material and is characterized by prolonged fever and abdominal symptoms.
Pathogenesis and Clinical Course
After surviving the gastric acid barrier, S. Typhi penetrates the intestinal epithelium, usually via M cells in Peyer’s patches of the ileum, and is engulfed by macrophages. The pathogen is adapted to human hosts and resists killing within phagocytes, enabling it to disseminate through the lymphatic and hematogenous routes. Bacteria replicate in the liver, spleen and bone marrow, leading to sustained bacteremia and a gradual rise in body temperature. Patients often develop malaise, headache, anorexia and relative bradycardia. Constipation is common early in illness; later stages may involve diarrhea. Rose‑colored macules may appear on the trunk. Without treatment, the disease can progress to intestinal ulceration, hemorrhage or perforation. Diagnosis relies on blood cultures and serologic tests; Widal test detects antibodies but has limited specificity. Effective therapy includes fluoroquinolones or third‑generation cephalosporins, although antimicrobial resistance is increasing. Typhoid fever is preventable through improved sanitation and vaccination with Vi polysaccharide or live oral Ty21a vaccines.
Clinical Manifestations and Epidemiology
Typhoid fever has caused major outbreaks in regions with inadequate water and sanitation. Asymptomatic carriers excrete S. Typhi from the gallbladder for years, serving as reservoirs; the most famous example is Mary Mallon (“Typhoid Mary”), who infected numerous individuals while working as a cook in early 20th‑century New York. The term “enteric fever” encompasses typhoid and paratyphoid fevers, the latter caused by Salmonella Paratyphi A, B or C, which generally produce milder disease. Endemic areas include parts of South Asia, Africa and Latin America. Water chlorination, hand hygiene and proper sewage disposal reduce transmission. Public health surveillance and vaccination campaigns are key to control, especially given the emergence of multidrug‑resistant strains.
Prompt recognition and treatment of typhoid fever prevent complications and curtail transmission. Enhancing sanitation and vaccination programs remains critical for reducing the global burden of this human‑adapted pathogen.
Related Terms: Salmonella Typhi, enteric fever, Salmonella Paratyphi, carrier state, Widal test