Serological studies on cholera patients and their household contacts in Calcutta in 1968. Joint ICMR-GWB-WHO Cholera Study Group, Calcutta, India.

Vibriocidal and agglutination tests have been performed, using a microtechnique, on 170 pairs of sera obtained, at intervals of 13-26 days, from bacteriologically proven cholera patients and their contacts, carriers and vibrio-negative contacts. Of the carriers, 44%-46% of those with low initial vibriocidin titres (</= 1:80) and 28%-37% of those having high initial titres (</= 1:160) showed a 4-fold or greater rise in vibriocidal titres. Carriers and negative contacts exhibited almost similar pictures. With an increase in the number of carriers per household, a larger number of negative contacts developed significant titres in their second samples. In general, initial titres increased with age, but were highest in the 10-25-years age-group: however, 30% of children below 10 years of age had titres >/= 1:640. The results indicated that individuals with high titres might become carriers but may not suffer from overt cholera.The investigation also showed that retrospective diagnosis of cholera infection in a highly endemic area should not depend on serology alone.