The new england journal of medicine established in 1812 february 14, 2013 vol. 368 no. 7 Cholera Surveillance during the Haiti Epidemic — The First 2 Years Ezra J. Barzilay, M.D., Nicolas Schaad, M.P.H., Roc Magloire, M.D., Kam S. Mung, M.D., Jacques Boncy, M.D., Georges A. Dahourou, Pharm.D., Eric D. Mintz, M.D., Maria W. Steenland, M.P.H., John F. Vertefeuille, Ph.D., and Jordan W. Tappero, M.D. Abstr act Background In October 2010, nearly 10 months after a devastating earthquake, Haiti was stricken From the Centers for Disease Control and by epidemic cholera. Within days after detection, the Ministry of Public Health and Prevention, Atlanta (E.J.B., N.S., G.A.D., E.D.M., M.W.S., J.F.V., J.W.T.); and Ministère Population established a National Cholera Surveillance System (NCSS). de la Santé Publique et de la Population, Direction d’Epidémiologie, des Labora- Methods toires, et de la Recherche (R.M.), Pan American Health Organization (K.S.M.), The NCSS used a modified World Health Organization case definition for cholera Ministère de la Santé Publique et de la that included acute watery diarrhea, with or without vomiting, in persons of all ages Population, Laboratoire National de Santé residing in an area in which at least one case of Vibrio cholerae O1 infection had been Publique (J.B.), and Centers for Disease Control and Prevention (Haiti Office) confirmed by culture. (G.A.D., J.F.V.) — all in Port-au-Prince, Haiti. Address reprint requests to Dr. Bar- Results zilay at the Centers for Disease Control and Prevention, 1600 Clifton Rd. NE, MS: Within 29 days after the first report, cases of V. cholerae O1 (serotype Ogawa, biotype A-05, Atlanta, GA 30329, or at ebarzilay@ El Tor) were confirmed in all 10 administrative departments (similar to states or cdc.gov. provinces) in Haiti. Through October 20, 2012, the public health ministry reported This article was published on January 9, 604,634 cases of infection, 329,697 hospitalizations, and 7436 deaths from cholera 2013, at NEJM.org. and isolated V. cholerae O1 from 1675 of 2703 stool specimens tested (62.0%). The N Engl J Med 2013;368:599-609. cumulative attack rate was 5.1% at the end of the first year and 6.1% at the end of DOI: 10.1056/NEJMoa1204927 the second year. The cumulative case fatality rate consistently trended downward, Copyright © 2013 Massachusetts Medical Society. reaching 1.2% at the close of year 2, with departmental cumulative rates ranging from 0.6% to 4.6% (median, 1.4%). Within 3 months after the start of the epidemic, the rolling 14-day case fatality rate was 1.0% and remained at or below this level with few, brief exceptions. Overall, the cholera epidemic in Haiti accounted for 57% of all cholera cases and 53% of all cholera deaths reported to the World Health Organiza- tion in 2010 and 58% of all cholera cases and 37% of all cholera deaths in 2011. Conclusions A review of NCSS data shows that during the first 2 years of the cholera epidemic in Haiti, the cumulative attack rate was 6.1%, with cases reported in all 10 depart- ments. Within 3 months after the first case was reported, there was a downward trend in mortality, with a 14-day case fatality rate of 1.0% or less in most areas. n engl j med 368;7 nejm.org february 14, 2013 599 The New England Journal of Medicine Downloaded from nejm.org by NICOLETTA TORTOLONE on February 13, 2013. For personal use only. No other uses without permission. Copyright © 2013 Massachusetts Medical Society. All rights reserved. T h e new england journal o f medicine n October 19, 2010, the Haitian veillance System and the Internally Displaced Ministry of Public Health and Popula- Persons Surveillance System.11,12 Though these Otion’s Directorate of Epidemiology, Labo- systems reported weekly on cases of acute watery ratory and Research was notified of unusually diarrhea, they were not designed to handle the high numbers of patients from 2 of Haiti’s 10 ad- magnitude and type of data needed to track an ministrative departments (similar to states or prov- emergent national epidemic. Thus, there was a inces), Artibonite and Centre, who had presented need for a cholera-specific surveillance system with acute watery diarrhea and dehydration, in that could capture and summarize daily reports, some cases leading to death.1 On October 21, be immediately operational in affected areas, 2010, the National Public Health Laboratory and be rapidly scalable. This event-based surveil- identified toxigenic Vibrio cholerae O1 (serotype lance system built on the existing infrastructure Ogawa, biotype El Tor) in stool specimens from for health care monitoring and evaluation and several patients.2 The health ministry immedi- benefited from lessons learned from activities ately informed the public, the Pan American after the earthquake. This article describes the Health Organization (PAHO), and other interna- implementation of a National Cholera Surveillance tional authorities of the presence of laboratory- System (NCSS) and provides 2-year summary confirmed cholera in Haiti. There was an im- data for the epidemic through October 20, 2012. mediate need for surveillance data to track the anticipated epidemic and inform the public health Methods response. Compounding the difficulties of addressing Surveillance System rampant cholera were the challenges created by The NCSS was composed of both governmental the massive earthquake on January 12, 2010. and nongovernmental health facilities. Data were Despite multisectoral relief efforts, Haiti’s infra- collected and reported to the health ministry by structures for health care, water, and sanitation health authorities in the departments and com- were severely damaged, complicating an already munes. The health ministry was further respon- precarious situation. In 2008, an estimated 63% sible for the management, analysis, and dis- of the 9.8 million persons in Haiti had access to semination of all data. Technical staff from the an improved drinking water source (as defined Centers for Disease Control and Prevention (CDC) by the World Health Organization [WHO]), with and the PAHO contributed to the design and con- only 12% receiving piped, treated water; only tinuous improvement of the system. 17% had access to adequate sanitation.3 Cholera, a waterborne diarrheal disease that is rapidly Case Definition fatal in severe cases, had not been seen in Haiti The NCSS modified the WHO case definition for for more than a century, as the Caribbean region cholera of “acute watery diarrhea, with or with- was untouched by the cholera pandemic that be- out vomiting, in a patient aged 5 years or more” gan in Peru in 1991.4,5 The Haitian population to include persons of any age in a cholera-affect- had no previous exposure or acquired immunity ed department.13,14 Cases were stratified accord- to toxigenic V. cholerae.5 Compounding factors, ing to age (<5 years or ≥5 years), which allowed such as the prevalence of malnutrition, blood for the tracking of the number of cases that met group O, and hypochlorhydria, may have further the WHO case definition. A cholera-affected de- contributed to disease severity.6-8 The Haitian partment was defined as one in which V. cholerae epidemic strain was identified as a variant strain O1 had been isolated from at least one stool cul- of the El Tor biotype, containing the toxin type ture at the national laboratory.15 found in the Classic biotype, a variant strain that has been associated with more severe illness.9,10 Laboratory Testing Attaining the internationally accepted goal of a Samples of stool were tested by a commercial cholera case fatality rate of 1.0% or less was made rapid diagnostic test for V. cholerae O1 and O139 more challenging because of these conditions.1 (Crystal VC Dipstick, Span Diagnostics) and were In response to the earthquake, the health min- inoculated onto thiosulfate–citrate-bile salts– istry established two syndrome-based disease- sucrose agar.14 V. cholerae strains were identified, surveillance systems: the National Sentinel Sur- serotyped, and tested for antimicrobial suscepti- 600 n engl j med 368;7 nejm.org february 14, 2013 The New England Journal of Medicine Downloaded from nejm.org by NICOLETTA TORTOLONE on February 13, 2013. For personal use only. No other uses without permission. Copyright © 2013 Massachusetts Medical Society. All rights reserved. Cholera Surveillance in Haiti — The First 2 Years bility at the national laboratory with the use of hospitalized cases. Average 14-day case fatality standard methods.16 All 10 departments were re- rates were calculated as the ratio of new deaths quested to provide periodic convenience samples to the number of new cases during the preceding of stool specimens from patients meeting the 14-day period. case definition to confirm the ongoing presence NCSS data were used to create weekly reports of toxigenic V. cholerae and for antimicrobial sus- detailing commune-level data, including tables ceptibility testing to inform and monitor the de- and maps of weekly incidence and cumulative velopment of treatment guidelines over the course attack rates, calculated as the ratio of the total of the epidemic. Since April 2012, an increasing number of cases (including community deaths) number of stool specimens have been collected in to the overall population. These maps were pro- a more systematic fashion through a laboratory- duced in ArcGIS 10 (ESRI). Reports and maps enhanced, health care facility–based sentinel were posted on the website of the health minis- surveillance system for acute watery diarrhea try (www.mspp.gouv.ht). launched by the national laboratory at four sites in three departments.17 Results Hospitalizations and Deaths Surveillance System Data were also collected on hospitalizations and Data that were collected for the 10 days from deaths.