A total of 631 serum samples collected in 1969, 1979, and 1989 from adults and children were screened for Helicobacter pylori by Western blot analysis. Results showed that H. pylori seroprevalence has become less frequent over the 20-year period. By studying seropositivity by year of birth, the magnitude of a cohort effect of H. pylori seropositivity was estimated. The odds of being seropositive decreased by 26% per decade, P = .008 (95% confidence interval, 8%-41%). Estimates of seroprevalence adjusted for both age-specific variation and the cohort effect suggest that most seropositivity in adults occurs by the age of 15 years. The implication of these findings is that H. pylori infection is becoming less frequent and is predominantly acquired in childhood.

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In September and October 1978, after a case of cholera had been discovered in southwestern Louisiana, 10 more Vibrio cholerae O-Group 1 infections were detected in four additional clusters. All 11 infected persons had recently eaten cooked crabs from five widely separated sites in the coastal marsh, and a matched-triplet case-control study showed a significant relation between cholera and eating such crabs (P = 0.007). V. cholerae O1 was isolated from estuarine water, from fresh shrimp, from a leftover cooked crab from a patient's refrigerator, and from sewage in six towns, including three without identified cases. All isolates in Louisiana and an isolate from a single unexplained case in Texas in 1973 were biotype El Tor and serotype inaba; they were hemolytic and of a phage type unique to the United States--suggesting that the organism persisted undetected along the Gulf Coast for at least five years.

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