viernes, 19 de noviembre de 2010

Update: Cholera Outbreak --- Haiti, 2010



Update: Cholera Outbreak --- Haiti, 2010
Weekly
November 19, 2010 / 59(45);1473-1479


On October 19, 2010, the Haitian Ministry of Public Health and Population (MSPP) was notified of unusually high numbers of patients from Artibonite and Centre departments who had acute watery diarrhea and dehydration, in some cases leading to death. Within 4 days, the National Public Health Laboratory (LNSP) in Haiti isolated Vibrio cholerae serogroup O1, serotype Ogawa, from stool specimens obtained from patients in the affected areas by an investigation team from MSPP and CDC Haiti. This report describes the investigation of the initial cases, the ongoing outbreak of cholera in Haiti, and initial control measures. Since the initial identification of cholera, the outbreak has expanded to include cases in seven of Haiti's 10 departments and the capital city of Port-au-Prince. As of November 13, MSPP had reported 16,111 persons hospitalized with acute watery diarrhea and 992 cholera deaths, 620 of which occurred among hospitalized patients. Prevention and control measures implemented by MSPP with assistance from governmental and nongovernmental partners include 1) providing better access to treated drinking water; 2) providing education on improvement of sanitation, hygiene, and food preparation practices; 3) advising ill persons to begin using oral rehydration solution immediately and seek health care at the onset of watery diarrhea; 4) enhancing cholera treatment capacity at existing health-care institutions; and 5) establishing cholera treatment centers.

Initial Epidemiologic Investigation

During October 21--23, an investigation was conducted by MSPP and CDC Haiti at five hospitals in Artibonite Department. The first patients with diarrhea and severe dehydration were admitted to these hospitals on October 19. During October 20--22, the majority of patients at these hospitals with diarrhea and severe dehydration were aged >5 years, and the majority of the patients at these hospitals who died were aged >5 years, suggesting that the outbreak might be caused by cholera.

On October 19 and 20, stool specimens from patients in health facilities in Artibonite and Centre departments were brought to LNSP, where rapid tests on eight specimens were positive for V. cholerae O1. LNSP identified V. cholerae serogroup O1, serotype Ogawa, from three specimens on October 22. Following confirmation of cholera, hospital staff members and public health authorities advised community members, including patients and their families, to boil or chlorinate their water before drinking.

During October 21--23, the investigative team used a standardized questionnaire to interview a convenience sample of 27 patients in the five hospitals in Artibonite Department. Most of these patients resided or worked in rice fields in communities located alongside a stretch of the Artibonite River approximately 20 miles (32 kilometers) long (Figure 1). Eighteen (67%) of the 27 hospitalized patients reported consuming untreated water from the river or canals before illness onset; 18 (67%) did not routinely use chlorine for treating water, and 21 (78%) practiced open defecation.

Cholera Surveillance and Laboratory Findings

A suspected case of cholera is defined as profuse, acute watery diarrhea in a patient. A confirmed case of cholera requires laboratory confirmation by culture of V. cholerae. When a department reports a case of laboratory-confirmed cholera, the department is declared "cholera affected." Only reports from cholera-affected departments are tallied and included in the MSPP daily surveillance summaries.

Since the initial identification of cholera in Artibonite and Centre departments, the outbreak has expanded to include cases in five additional departments and the capital city; cases have been reported in seven of 10 departments (Artibonite, Centre, Nord, Nord' Ouest, Nord' Est, Ouest, and Sud) and Port-au-Prince. As of November 13, MSPP had reported 16,111 persons hospitalized with acute watery diarrhea and 992 cholera deaths, 620 of which occurred among hospitalized patients (case-fatality rate among hospitalized patients: 3.8%) (Figure 2). Cases and deaths have been reported primarily from Artibonite department (63% of cases and 62% of deaths).

At LNSP, the outbreak isolates were identified as V. cholerae serotype O1, serogroup Ogawa, and selected specimens were sent to CDC for confirmation and additional analyses. As of November 13, CDC had isolated V. cholerae from 14 specimens received from LNSP. All isolates were identified phenotypically and characterized by serotyping, biotyping, antimicrobial susceptibility testing, and by pulsed-field gel electrophoresis (PFGE), performed using a protocol developed by PulseNet International, the international molecular subtyping network for foodborne and waterborne disease surveillance. Additionally, the isolates were characterized genetically for the presence and subtype of certain virulence factors (e.g., the cholera toxin, genes specific for strains associated with the ongoing cholera pandemic, and antimicrobial resistance genes). The 14 isolates associated with the outbreak in Haiti were indistinguishable by all laboratory methods, revealing that the outbreak strain was V. cholerae serogroup O1, serotype Ogawa, biotype El Tor, and PulseNet PFGE pattern combination KZGN11.0092/KZGS12.0088. The strain possessed a cholera toxin variant that was first seen in cholera strains of the classical biotype. As of November 13, data indicated that a single strain caused illness among the 14 persons from Artibonite Department. If these isolates are representative of those currently circulating in Haiti, the findings suggest that V. cholerae was likely introduced into Haiti in one event. V. cholerae strains that are indistinguishable from the outbreak strain by all methods used have previously been found in countries in South Asia and elsewhere. PFGE analysis on isolates obtained from cholera patients who became ill in other departments in Haiti is ongoing.

Whole genome sequence (WGS) analysis of three isolates from the current outbreak, and other V. cholerae strains is under way. Comparative WGS analysis is the ultimate discriminatory subtyping tool because it detects any and all genetic difference among isolates. Limited WGS data are available currently for V. cholerae. Comprehensive libraries of V. cholerae genomes from epidemiologically or geographically related and unrelated isolates are needed before the sequence data of the Haiti outbreak strain can be interpreted in the proper epidemiologic context.

A representative outbreak isolate has been deposited into the American Type Culture Collection (ATCC) under the strain number BAA- 2163, and the draft genome sequences of the three isolates have been deposited into the GenBank database under the accession numbers AELH00000000, AELI00000000, and AELJ00000000.* Genome sequences will be updated in this database as they become available. Availability of an isolate and WGS of the Haiti outbreak strain as a public resource should facilitate rapid additional characterization by the global scientific community.

Initial antimicrobial susceptibility testing performed at LNSP indicated that all isolates were susceptible to tetracycline (a proxy for doxycycline) but resistant to sulfisoxazole and nalidixic acid. Additional antimicrobial susceptibility testing at CDC on 14 isolates determined that these isolates demonstrated susceptibility to azithromycin, reduced susceptibility to ciprofloxacin, and resistance to furazolidone. Antimicrobial treatment is recommended for severe cholera cases only. Recommended regimens include single-dose doxycycline (for nonpregnant adults and children), azithromycin (for pregnant women and all others), and other antimicrobial agents.†

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Update: Cholera Outbreak --- Haiti, 2010

Update: Cholera Outbreak --- Haiti, 2010

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