Typhoid Fever in depth.

Overview

Typhoid fever is a life-threatening systemic bacterial infection caused by Salmonella enterica serotype Typhi, transmitted exclusively through the fecal-oral route via contaminated food and water. It causes 9–11 million illnesses and approximately 110,000 deaths annually, predominantly in South and Southeast Asia, sub-Saharan Africa, and Latin America. The clinical hallmark is a stepwise rising fever reaching 39–40°C, accompanied by headache, abdominal pain, and the distinctive "rose spots" rash. Without treatment, the case fatality rate reaches 10–30%; with appropriate antibiotics, it falls to 1–4%.

The global burden of typhoid is concentrated in low-income settings with inadequate water, sanitation, and hygiene (WASH) infrastructure. Children aged 2–14 years bear the greatest burden. A critical and growing threat is extensively drug-resistant (XDR) typhoid, which emerged in Pakistan in 2016 and has spread internationally — resistant to ampicillin, chloramphenicol, co-trimoxazole, fluoroquinolones, and third-generation cephalosporins simultaneously, leaving carbapenems as the only reliable oral treatment.

History & Origin

Typhoid fever has affected human populations since antiquity. Some historians argue that Thucydides' description of the "Plague of Athens" (430 BC) matches typhoid. The name derives from Greek "typhos" (smoke or stupor), referring to the neurological symptoms. The bacterium was isolated by Karl Eberth in 1880. Almroth Wright developed the first effective typhoid vaccine in 1896, used extensively in WWI military campaigns where typhoid historically killed more soldiers than combat.

Mary Mallon ("Typhoid Mary"), an asymptomatic chronic carrier in early 20th century New York, infected at least 51 people as a cook, becoming one of history's most famous public health cases. The mid-20th century saw dramatic reductions in typhoid in high-income countries with improved sanitation. However, the emergence of multidrug-resistant (MDR) typhoid in the 1980s–1990s, followed by XDR typhoid in Pakistan in 2016, represents a serious modern threat.

Transmission

Typhoid is transmitted exclusively through ingestion of S. Typhi-contaminated food or water. There is no animal reservoir — humans are the only natural host.

• Contaminated water: Untreated or inadequately treated drinking water contaminated with sewage is the most common transmission route in endemic regions.
• Contaminated food: Food prepared by chronic carriers, or raw produce irrigated with contaminated water, especially raw shellfish, fruits, and vegetables.
• Chronic carriers: Approximately 3–5% of typhoid cases become chronic carriers who shed S. Typhi in stool (or urine, in those with concurrent gallbladder disease) for more than one year after acute illness — often without symptoms.
• Direct contact: Person-to-person transmission via fecal-oral route possible in settings with poor hygiene.
• Infectious dose: relatively low (~10³–10⁶ organisms); higher dose associated with shorter incubation and greater severity.

Symptom Timeline

Incubation: 7–14 days (range 3–60 days). Classical typhoid has a characteristic stepwise progression over 4 weeks.

Diagnosis

• Blood culture: Gold standard. Sensitivity 60–80% in first week; lower thereafter. Requires 5–10 mL blood. Culture bottles must be incubated 5–7 days. Bacteremia peaks in weeks 1–2.
• Bone marrow culture: Most sensitive (90–95%) even after antibiotic initiation; used when blood cultures are negative in strongly suspected cases.
• Stool and urine culture: Positive from weeks 2–3; useful for diagnosing carrier state.
• Widal test (serology): Widely used but poorly specific — significant false positives in endemic areas. A 4-fold rise in titers between acute and convalescent sera is more meaningful than a single high titer. Not recommended as sole diagnostic test.
• Rapid diagnostic tests: Typhi-Dot (IgM/IgG), TUBEX (anti-O9 antibodies) — sensitivity 70–80%, more useful than Widal but not as reliable as culture.
• CBC: Leukopenia (low WBC) is characteristic (paradoxically low given bacterial infection). Anemia, thrombocytopenia in severe disease.
• PCR: Highly sensitive and specific; can detect XDR strains and resistance genes. Increasingly available in endemic areas.

Treatment

Antibiotic treatment dramatically reduces mortality. Choice depends on local resistance patterns — always base on culture and sensitivity results when available.

Susceptible Typhoid

• Fluoroquinolones (ciprofloxacin, ofloxacin): Historically first-line; 5–7 days. Resistance now >80% in South Asia — no longer reliable there.
• Azithromycin: Now preferred oral treatment in uncomplicated typhoid; 7 days; fewer GI side effects; effective against MDR strains.
• Chloramphenicol, ampicillin, co-trimoxazole: Previously standard; now often resistant.

MDR Typhoid

• Third-generation cephalosporins (ceftriaxone IV): First-line for severe/MDR typhoid; 10–14 days IV; highly effective.
• Azithromycin: Effective oral option for MDR uncomplicated typhoid.

XDR Typhoid (Pakistan-origin H58 strain)

• Carbapenems (meropenem, imipenem): Currently the only reliable treatment for XDR typhoid; IV administration; requires hospital admission.
• XDR typhoid resistant to: ampicillin, chloramphenicol, co-trimoxazole, fluoroquinolones, AND third-generation cephalosporins.
• Azithromycin and carbapenems remain active against XDR strains as of 2024.

Supportive Care

• Adequate hydration; IV fluids if oral intake compromised
• Paracetamol for fever management (avoid NSAIDs due to GI bleeding risk)
• Dexamethasone for severe typhoid with encephalopathy (reduces mortality)
• Surgical management for intestinal perforation

Prevention & Vaccines

• Typhoid Conjugate Vaccines (TCV) — Typbar-TCV, PedaTyph: WHO-prequalified. Single-dose injectable; protects from age 6 months. 81–87% efficacy in field trials. Recommended by WHO for mass vaccination in high-burden countries. Preferred vaccine for children.
• Vi polysaccharide vaccine (Vi-PS): Injectable; single dose; 55–72% efficacy; not immunogenic under age 2; requires boosters every 2–3 years.
• Ty21a oral vaccine: Live attenuated oral vaccine; 4 capsules on alternate days; 51–67% efficacy; approved from age 6 years; requires refrigeration; boosters every 5 years.
• WASH (Water, Sanitation, Hygiene): Safe water, adequate sewage treatment, and hand hygiene with soap are the most fundamental typhoid prevention measures. No vaccine is a substitute for WASH.
• Food safety: Boil or chemically treat drinking water; eat thoroughly cooked food; avoid raw produce in endemic areas; peel fruits yourself.
• Carrier identification and treatment: Treating chronic carriers (prolonged antibiotics ± cholecystectomy) can interrupt transmission chains.

Global Impact

Typhoid fever causes approximately 9–11 million illnesses and 110,000 deaths annually, with over 80% of the burden in South and Southeast Asia. The countries with the highest incidence are Pakistan, India, Bangladesh, Nepal, and several countries in sub-Saharan Africa. Children under 15 years bear a disproportionate burden.

The emergence of XDR typhoid — first identified in Hyderabad, Pakistan in 2016 — represents a critical threat. By 2024, XDR typhoid has spread globally through international travel, with cases detected in the UK, USA, Canada, Australia, and multiple other countries. If untreated appropriately, XDR typhoid carries significant mortality risk. The WHO has responded by accelerating TCV introduction in high-burden countries.

Pakistan launched the world's first nationwide XDR typhoid TCV campaign in 2019, vaccinating over 10 million children. Nepal, Zimbabwe, Liberia, and Ghana have followed with TCV introductions. WHO estimates that universal TCV introduction in 49 high-burden countries could prevent 2.1 million cases and 21,000 deaths over 10 years.

Frequently Asked Questions

Sources & Citations