In late 1992, an epidemic of cholera-like disease broke out in Tamil Nadu and Bengal affecting predominantly adults. Stool cultures grew non-agglutinable vibrios later named Vibrio cholerae O139. What distinguished this new serogroup epidemiologically from earlier El Tor O1 outbreaks?
- A It affected mainly children under 5 years because adults were immune
- B It affected adults predominantly because prior O1 immunity did not cross-protect against the new serogroup ✓
- C It produced only asymptomatic infections without watery diarrhoea
- D It spread exclusively by person-to-person contact rather than water
Correct answer: B. It affected adults predominantly because prior O1 immunity did not cross-protect against the new serogroup
Explanation
Vibrio cholerae O139 Bengal possesses a novel polysaccharide capsule and LPS antigen, so antibodies raised against O1 did not protect, and the susceptible pool included adults who had previously encountered O1. Clinically it caused typical rice-water diarrhoea indistinguishable from O1 cholera. Transmission remained faecal-oral through contaminated water and food, exactly like classical and El Tor cholera.
Reference: Park's Textbook of Preventive and Social Medicine, 27th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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