Waterborne transmission of epidemic cholera in Trujillo, Peru: lessons for a continent at risk

Abstract

The epidemic of cholera that began in Peru in January, 1991, marked the first such epidemic in South America this century. Subsequently, over 533,000 cases and 4700 deaths have been reported from nineteen countries in that hemisphere. We investigated the epidemic in Trujillo, the second largest city in Peru. Trujillo's water supply was unchlorinated and water contamination was common. Suspect cholera cases were defined as persons presenting to a health facility with acute diarrhoea between Feb 1, and March 31, 1991. We studied a cohort of 150 patients who had been admitted to hospital and conducted a matched case-control study with 46 cases and 65 symptom-free and serologically uninfected controls; we also carried out a water quality study. By March 31, 1991, 16,400 cases of suspected cholera (attack rate 2.6%), 6673 hospital admissions, and 71 deaths (case-fatality rate 0.4%) had been reported in the province of Trujillo. 79% of stool cultures of patients with diarrhoea presenting to a single hospital yielded Vibrio cholerae O1. In the case-control study, drinking unboiled water (odds ratio [OR] 3.1, 95% confidence interval [CI] 1.3-7.3), drinking water from a household water storage container in which hands had been introduced into the water (4.2, 1.2-14.9), and going to a fiesta (social event) (3.6, 1.1-11.1) were associated with illness. The water quality study showed progressive contamination during distribution and storage in the home: faecal coliform counts were highest in water from household storage containers and lowest in city well water. V cholerae O1, biotype El Tor, serotype Inaba, was isolated from three city water samples. Cholera control measures in Trujillo should focus on treatment of water and prevention of contamination during distribution and in the home. Trujillo's water and sanitation problems are common in South America; similar control measures are needed throughout the continent to prevent spread of epidemic cholera.

PIP: Researchers conducted various studies simultaneously in Trujillo. Peru (population 626,456) in March 1991 to set up a cholera surveillance system and to determine clinical characteristics of suspect cholera cases, modes of transmission, and municipal water quality during distribution and storage. These studies occurred after the population received information on how to avoid cholera. The cholera attack rate for the 1st 2 months of the epidemic stood at 2.6% (16,400 cases). The case fatality rate was 0.4% (71 deaths). The median hours between onset of symptoms and arrival at Belen hospital were 12 hours. 56% of the patients were treated with oral rehydration solution before coming to the hospital and 13% with homemade rehydration solution. Laboratory personnel isolated toxigenic nonhemolytic Vibrio cholera 01, biotype El Tor, serotype Inaba from the rectal swabs of 79% of cholera patients. None of the hospital patients died. 29% of controls from the case control study claimed to not have witnessed a personal or household attack of diarrhea recently, yet their vibrocidal antibody titers indicated a recent cholera infection. 58% of cases drank unboiled water within 3 days of falling ill compared to only 28% of controls (matched odds ratio [OR] 3.1; p.05). Other significant risk factors (p.05) were drank water from container also used to dip hands (OR 4.2) and attended a fiesta (OR 3.6). There were significantly more total coliforms in water containers than tap water and municipal water (mean 794 vs. 6 and 1 respectively; p.05). The same was true for fecal coliforms (20 vs. 2 and 1 respectively). In conclusion, the drinking water was contaminated with V. cholera. Eventually the city should eliminate cross connections, provide continuous supplies of water at high pressure, and improve the sewage system.