typhoid fever

typhoid fever
Name	Typhoid fever
Caption	Salmonella enterica serovar Typhi
Field	Infectious disease (medical specialty)

typhoid fever. It is a life-threatening systemic infection caused by the bacterium Salmonella enterica serovar Typhi. The disease is characterized by a sustained high fever and severe gastrointestinal disturbances, and it remains a significant public health challenge in many parts of the developing world. Transmission occurs primarily through the ingestion of food or water contaminated with the feces of an infected person.

Signs and symptoms

The initial phase often presents with non-specific symptoms such as malaise, headache, and a stepwise rising fever. As the disease progresses, patients typically develop a sustained high fever, often accompanied by a relative bradycardia, known as Faget's sign. Characteristic rose spots may appear on the trunk, and profound gastrointestinal symptoms including constipation or pea-soup diarrhea, abdominal pain, and tenderness are common. In severe, untreated cases, complications can lead to life-threatening conditions like intestinal perforation, gastrointestinal hemorrhage, and encephalopathy.

Cause and transmission

The causative agent is the gram-negative bacterium Salmonella enterica serotype Typhi. Humans are the only known reservoir for this pathogen. Transmission is fecal-oral, primarily through the consumption of food or water contaminated by the feces or, less commonly, the urine of an infected individual or an asymptomatic chronic carrier. Notable historical carriers include Mary Mallon, known as "Typhoid Mary," who worked as a cook in New York City. The bacteria survive in water and can be spread by poor sanitation infrastructure, a major factor in outbreaks in regions like South Asia and sub-Saharan Africa.

Diagnosis

Definitive diagnosis requires the isolation of S. Typhi from a clinical specimen, most commonly through blood culture or bone marrow culture, the latter being more sensitive. The Widal test, which detects agglutinating antibodies against the O and H antigens of the bacterium, is used in some resource-limited settings but has limitations in specificity and sensitivity. Newer diagnostic methods include rapid serological tests and polymerase chain reaction assays. Differential diagnosis must consider other febrile illnesses such as malaria, dengue fever, and brucellosis.

Prevention

Prevention hinges on improved sanitation, access to clean water, and proper food hygiene. Two main types of vaccines are available for travelers and populations in endemic areas: the live attenuated oral vaccine, such as Ty21a, and the injectable Vi capsular polysaccharide vaccine. Major public health efforts by organizations like the World Health Organization and Gavi, the Vaccine Alliance focus on vaccination campaigns in endemic countries. The historical importance of sanitation was demonstrated by the public health reforms of John Snow in London and the work of Joseph Bazalgette on the London sewerage system.

Treatment

The cornerstone of treatment is appropriate antibiotic therapy. For decades, first-line agents included chloramphenicol, ampicillin, and trimethoprim/sulfamethoxazole. However, the emergence and spread of multidrug-resistant strains, particularly in South Asia, has necessitated the use of newer antibiotics like fluoroquinolones (e.g., ciprofloxacin) and third-generation cephalosporins (e.g., ceftriaxone). Azithromycin is also an effective option. Supportive care with rehydration and nutritional support is critical, and surgical intervention may be required for complications like intestinal perforation.

Epidemiology

It is a major global health issue, with an estimated 11–21 million cases and 128,000–161,000 deaths annually. The highest burden of disease is in South Asia, Southeast Asia, and sub-Saharan Africa, where access to clean water and sanitation is limited. Outbreaks are often associated with natural disasters, conflict, or large gatherings. Significant historical epidemics have occurred, including during the American Civil War and the Spanish-American War. International travel from endemic regions to areas like the United States and Western Europe accounts for most cases in developed countries.

Category:Infectious diseases Category:Waterborne diseases Category:Neglected tropical diseases