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Epidemiologic Notes and Reports Cholera -- New York, 1991

Through June 26, 1991, cholera has been reported from seven countries in the Western Hemisphere: Brazil, Chile, Colombia, Ecuador, Mexico, Peru, and the United States. In the United States, a total of 14 confirmed cases of epidemic-associated cholera have been reported among persons in Florida (one) (1), Georgia (one) (2), New Jersey (eight) (1), and New York (four). This report summarizes information regarding the four cases reported in New York and describes a new laboratory procedure used to confirm the vehicle of transmission in this outbreak.

On April 26, 1991, a 57-year-old man (patient B) was hospitalized in New York City with a 2-day history of diarrhea; stool culture yielded Vibrio cholerae O1. An investigation by the New York City Department of Health identified additional cases among his family and friends. The first person to become ill was a man (patient A) who had returned from Ecuador on April 21 and had onset of watery diarrhea April 22. Although he sought care from a physician, he was not hospitalized, and a stool culture was not obtained.

On April 24, three other persons (patients B, C, and D) had onset of diarrhea. All patients had laboratory evidence of infection with V. cholerae O1. A stool culture from patient C, a woman, yielded V. cholerae O1. Convalescent phase blood samples from patient D, a woman, and patient A had vibriocidal antibody titers greater than or equal to 1:640, indicating recent V. cholerae O1 infection. The New York City Department of Health Laboratory and CDC identified the isolates as toxigenic V. cholerae O1, biotype El Tor, serotype Inaba--the serotype that is causing epidemic cholera in South America.

Patients B, C, and D had not recently visited South America. However, on the evening of April 22 they had eaten a salad containing crab meat from crabs that had been brought from Ecuador by patient A. The crabs had been purchased by patient A at a pier in Guayaquil, Ecuador, on April 20, then boiled and shelled; meat and claws were then stored in a plastic bag in a freezer. On April 21, when patient A returned to New York, he carried the bag in his suitcase; on arrival, the meat and claws were still frosted and were placed in a freezer overnight. On April 22, the crab meat was thawed in a double-boiler for 15-20 minutes. Two hours later, without further cooking, the crab was served in a crab salad and as cold crab in the shell. The crab was consumed during a 6-hour period by patients B, C, and D and by four persons who remained well. Patient A had onset of diarrhea before eating the crab meat but ate after patients B, C, and D had eaten; he did not assist in preparing the food.

Four samples of crab were obtained for culture, including a claw, two pieces of meat that had remained in the plastic bag, and juice saved when the crab meat was thawed for the crab salad. Standard culture procedures were negative for V. cholerae O1 at the New York City Department of Health and CDC. However, use of the polymerase chain reaction (PCR) technique with primers recently constructed at CDC enabled dection of the V. cholerae O1 toxin gene in one of the pieces of crab meat from the plastic bag. Reported by: R Roman, MPH, M Middleton, S Cato, E Bell, KR Ong, MD, Commission on Disease Intervention; R Gruenewald, PhD, A Ferguson, MS, A Ramon, MD, Bur of Laboratories, New York City Dept of Health. Enteric Diseases Br, Div of Bacterial and Mycotic Diseases, National Center for Infectious Diseases, CDC.

Editorial Note

Editorial Note: Epidemic cholera had not been reported in South America during the 1900s until January 1991, when cholera was reported from several locations in Peru (3). As of July 24, 1991, 257,399 probable cholera cases and 2697 cholera-associated deaths have been reported to the Pan American Health Organization from seven countries (Table 1). The cases in New York bring to 14 the total number of confirmed cholera cases in the United States associated with the epidemic in South America; in addition, these cases are the second episode of transmission of V. cholerae O1 associated with crabs brought back by a traveler from South America (1). The Food and Drug Administration monitors seafood imported into the United States; no cases of cholera in the continental United States have been linked to commercially imported food products.

Patient A probably became infected with V. cholerae O1 while in Ecuador because he had onset of illness within 24 hours of returning to New York. Patients B, C, and D were probably infected by eating the crab. Patient A was unlikely to have contaminated the crab because his illness began after the crab had been cooked, frozen, and packaged, and he touched the crab meat again only after the others had eaten. Secondary spread from patient A is unlikely because person-to-person spread of cholera is infrequent--especially in settings where adequate access to water for washing and sanitation facilities exist. Since 1961, more than 100 domestically acquired and imported cases of cholera have been reported to CDC; none of these cases has been associated with person-to-person spread (CDC, unpublished data).

Crabs are a likely vehicle for transmission of cholera and may be contaminated with V. cholerae O1 before or after harvest. Vibrios can survive in crabs boiled for up to 8 minutes (4), and undercooked crabs have caused several previous outbreaks (2,4). V. cholerae O1 biotype El Tor strains multiply rapidly at room temperature in cooked shellfish (5). In this report, vibrios that survived boiling in Ecuador or that contaminated the meat during shelling may have multiplied during transport or while the crab salad was held at ambient temperature.

Standard culture procedures can detect only viable organisms; in contrast, PCR can detect DNA from nonviable organisms. Because of the freezing and thawing, V. cholerae O1 organisms in the crab may not have been viable. However, PCR analysis indicated that the crabs from the outbreak had been contaminated with toxigenic V. cholerae O1. The PCR procedure and other new laboratory tests are potentially important tools for investigating outbreaks of cholera.

The cholera outbreaks in New Jersey (1) and New York prompted an ongoing educational campaign to discourage travelers from returning from infected areas (including Peru, Ecuador, and Colombia) with perishable seafood and other high-risk food items. This campaign includes publication by CDC of a travel advisory in English and Spanish and the distribution of letters to airline passengers traveling to and returning from these countries. Newspapers and radio and television stations in the New Jersey/New York area have also helped publicize this message. No additional cases of cholera associated with food brought back from South America have been reported.

A CDC ``travelers' hot line'' is available in English and Spanish for persons planning travel to Central and South America: the telephone numbers are (404) 332-4559 (English) and (404) 330-3132 (Spanish).


  1. CDC. Cholera--New Jersey and Florida. MMWR 1991;40:287-9.

  2. CDC. Importation of cholera from Peru. MMWR 1991;40:258-9.

  3. CDC. Cholera--Peru, 1991. MMWR 1991;40:108-10.

  4. Blake PA, Allegra DT, Snyder JD, et al. Cholera--a possible endemic focus in the United States. N Engl J Med 1980;302:305-9.

  5. Kolvin JL, Roberts D. Studies on the growth of Vibrio cholerae biotype El Tor and biotype classical in foods. J Hygiene 1982;89:243-52.

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