Typhoid Fever

🦠 What Is Typhoid Fever?

Typhoid fever is a life-threatening systemic infection caused by the bacterium Salmonella enterica serotype Typhi. Unlike common food poisoning caused by other Salmonella species, typhoid fever specifically refers to this invasive, gram-negative bacillus that infects only humans.

The pathogen is a facultative intracellular organism that survives and multiplies within macrophages and other phagocytic cells, allowing it to disseminate throughout the body via the lymphatic system and bloodstream.

🔄 How It Spreads

Typhoid fever is transmitted exclusively through the fecal-oral route. The bacterium cannot survive in the environment for long periods outside a human host.

• Contaminated water: Drinking water contaminated with sewage containing S. Typhi is the most common transmission method
• Contaminated food: Food prepared by infected individuals who did not wash hands properly after defecation
• Asymptomatic carriers: Individuals who harbor S. Typhi in their gallbladder and shed bacteria in stool for years ("Typhoid Mary" phenomenon)
• Direct contact: Rarely, through oral-anal sexual contact with an infected person

The incubation period ranges from 6-30 days, typically 8-14 days, during which the bacteria penetrate intestinal mucosa, invade Peyer's patches, and enter the bloodstream.

⚠️ Symptoms & Disease Progression

Symptoms develop in progressive stages if untreated:

Week 1:

• Stepwise fever pattern (rising daily)
• Relative bradycardia (Faget's sign)
• Rose spots on trunk (30% of cases)
• Headache, malaise, abdominal pain

Week 2-3:

• Sustained high fever (39-41°C)
• Hepatosplenomegaly
• Relative bradycardia persists
• Abdominal distension and tenderness

Week 3-4:

• Intestinal hemorrhage (10-20% of cases)
• Intestinal perforation (1-3% of cases, potentially fatal)
• Typhoid encephalopathy
• Myocarditis

Complications include:

• Gastrointestinal bleeding
• Peritonitis from perforation
• Pneumonia
• Meningitis
• Disseminated intravascular coagulation (DIC)

🌍 Global Distribution & Epidemiology

Typhoid fever remains endemic in regions with poor sanitation:

• Endemic areas: South Asia (India, Pakistan, Bangladesh), Southeast Asia, Africa, Latin America
• Incidence: Estimated 11-21 million cases annually, 128,000-161,000 deaths
• Case fatality rate: 1-4% with treatment, up to 20% untreated
• Children: Highest burden in school-age children (5-15 years)
• Seasonality: Peaks during monsoon/rainy seasons in endemic areas

Risk factors:

• Travel to endemic areas
• Poor sanitation infrastructure
• Lack of clean drinking water
• Close contact with infected individuals
• Consumption of street food in endemic areas

🔬 Diagnosis

Gold standard: Blood culture (positive in 60-80% of cases in first week)

Other diagnostic methods:

• Bone marrow culture (most sensitive, 80-95% positive)
• Stool culture (positive in 30-40% of cases, increases in later stages)
• Widal test (limited sensitivity/specificity, detects antibodies)
• Rapid diagnostic tests (detecting Vi antigen or IgM antibodies)

Laboratory findings:

• Leukopenia with relative lymphocytosis
• Elevated liver enzymes
• Positive blood cultures in first week become less sensitive after antibiotics

💊 Treatment & Prevention

Antibiotic therapy:

• First-line: Fluoroquinolones (ciprofloxacin, ofloxacin) - resistance emerging
• Alternative: Azithromycin (becoming preferred)
• Severe cases: Ceftriaxone or cefotaxime
• Duration: 7-14 days

Antibiotic resistance:

• Multidrug-resistant (MDR) strains emerging
• Extensively drug-resistant (XDR) strains reported

Prevention:

• Vaccination: Ty21a vaccine (oral) and Vi polysaccharide vaccine (injectable)
• Sanitation improvements: Clean water, proper sewage disposal
• Food hygiene: Proper cooking, handwashing
• Screening of food handlers in endemic areas

📊 High-Risk Groups

Travelers to endemic areas have highest risk. Children in endemic regions bear greatest burden. Immunocompromised individuals (HIV/AIDS) face severe outcomes. Healthcare workers treating infected patients. Close contacts of infected individuals. Food handlers in endemic areas. Military personnel deployed to endemic regions.

Chronic carriers (1-6% of infected individuals) require monitoring and sometimes cholecystectomy if antibiotic therapy fails.