A 28-year-old man from Delhi presents with a 2-week history of sustained fever, headache, and abdominal distension. Blood culture yields a gram-negative rod. Which Salmonella species is the most common cause of enteric fever in India?

Explanation

## Epidemiology of Enteric Fever in India **Key Point:** *Salmonella typhi* is responsible for approximately 70–80% of enteric fever cases in India, making it the most common causative agent. ### Comparative Frequency of Salmonella Species | Organism | Frequency in India | Clinical Features | Geographic Distribution | | --- | --- | --- | --- | | *S. typhi* | 70–80% | Sustained fever, rose spots, splenomegaly | Endemic in South Asia | | *S. paratyphi A* | 15–25% | Milder illness, shorter incubation | Rising in urban areas | | *S. paratyphi B* | 2–5% | Rare in India, more common in Europe | Sporadic cases | | *S. enteritidis* | <1% | Acute gastroenteritis, not enteric fever | Foodborne outbreaks | **High-Yield:** The ratio of *S. typhi* to *S. paratyphi* in India is approximately **3:1 to 4:1**, with *typhi* predominating in both urban and rural populations. ### Clinical Correlation **Clinical Pearl:** *S. typhi* typically causes the classic "enteric fever" syndrome with: - Sustained (continuous) fever lasting 3–4 weeks if untreated - Rose spots (faint maculopapular rash on trunk) - Relative bradycardia - Splenomegaly - Abdominal distension (as in this case) *S. paratyphi A*, though increasing in prevalence, still accounts for only 15–25% of cases and typically presents with a milder illness and shorter fever duration. **Mnemonic:** **TYPHI = The Year's Primary Hepatic Infection** — *S. typhi* is the primary (most common) cause of enteric fever in India.