Dynamics of cholera outbreaks in Great Lakes region of Africa, 1978-2008

Cholera Outbreak in Grande Comore: 1998-1999

In 1998, a cholera epidemic in east Africa reached the Comoros Islands, an archipelago in the Mozambique Channel that had not reported a cholera case for more than 20 years. In just a little over 1 year (between January 1998 and March 1999), Grande Comore, the largest island in the Union of the Comoros, reported 7,851 cases of cholera, about 3% of the population. Using case reports and field observations during the medical response, we describe the epidemiology of the 1998-1999 cholera epidemic in Grande Comore. Outbreaks of infectious diseases on islands provide a unique opportunity to study transmission dynamics in a nearly closed population, and they may serve as stepping-stones for human pathogens to cross unpopulated expanses of ocean.

Childhood Diarrhea Exhibits Spatiotemporal Variation in Northwest Ethiopia: A SaTScan Spatial Statistical Analysis

BACKGROUND

Childhood diarrhea continues to be a public health problem in developing countries, including Ethiopia. Detecting clusters and trends of childhood diarrhea is important to designing effective interventions. Therefore, this study aimed to investigate spatiotemporal clustering and seasonal variability of childhood diarrhea in northwest Ethiopia.

METHODS

Retrospective record review of childhood diarrhea was conducted using quarterly reported data to the district health office for the seven years period beginning July 1, 2007. Thirty three districts were included and geo-coded in this study. Spatial, temporal and space-time scan spatial statistics were employed to identify clusters of childhood diarrhea. Smoothing using a moving average was applied to visualize the trends and seasonal pattern of childhood diarrhea. Statistical analyses were performed using Excel® and SaTScan programs. The maps were plotted using ArcGIS 10.0.

RESULTS

Childhood diarrhea in northwest Ethiopia exhibits statistical evidence of spatial, temporal, and spatiotemporal clustering, with seasonal patterns and decreasing temporal trends observed in the study area. A most likely purely spatial cluster was found in the East Gojjam administrative zone of Gozamin district (LLR = 7123.89, p <0.001). The most likely spatiotemporal cluster was detected in all districts of East Gojjam zone and a few districts of the West Gojjam zone (LLR = 24929.90, p<0.001), appearing from July 1, 2009 to June 30, 2011. One high risk period from July 1, 2008 to June 30, 2010 (LLR = 9655.86, p = 0.001) was observed in all districts. Peak childhood diarrhea cases showed a seasonal trend, occurring more frequently from January to March and April to June.

CONCLUSION

Childhood diarrhea did not occur at random. It has spatiotemporal variation and seasonal patterns with a decreasing temporal trend. Accounting for the spatiotemporal variation identified in the study areas is advised for the prevention and control of diarrhea.

Nosocomial Cholera Outbreak in a Mental Hospital: Challenges and Lessons Learnt from Butabika National Referral Mental Hospital, Uganda

During the last four decades, Uganda has experienced repeated cholera outbreaks in communities; no cholera outbreaks have been reported in Ugandan health facilities. In October 2008, a unique cholera outbreak was confirmed in Butabika National Mental Referral Hospital (BNMRH), Uganda. This article describes actions taken to control the outbreak, challenges, and lessons learnt. We reviewed patient and hospital reports for clinical symptoms and signs, treatment and outcome, patient mental diagnosis, and challenges noted during management of patients and contacts. Out of 114 BNMRH patients on two affected wards, 18 cholera cases and five deaths were documented for an attack rate of 15.8% and a case fatality rate of 28%. Wards and surroundings were intensively disinfected and 96 contacts (psychiatric patients) in the affected wards received chemoprophylaxis with oral ciprofloxacin 500 mg twice daily until November 5, 2008. We documented a nosocomial cholera outbreak in BNMRH with a high case fatality of 28% compared with the national average of 2.4% for cholera outbreaks in communities. To avoid cholera outbreaks and potentially high mortality among patients in mental institutions, procedures for prompt diagnosis, treatment, disinfection, and prophylaxis are needed and preemptive use of oral cholera vaccines should be considered.

Relationship between Distinct African Cholera Epidemics Revealed via MLVA Haplotyping of 337 Vibrio cholerae Isolates

BACKGROUND

Since cholera appeared in Africa during the 1970s, cases have been reported on the continent every year. In Sub-Saharan Africa, cholera outbreaks primarily cluster at certain hotspots including the African Great Lakes Region and West Africa.

METHODOLOGY/PRINCIPAL FINDINGS

In this study, we applied MLVA (Multi-Locus Variable Number Tandem Repeat Analysis) typing of 337 Vibrio cholerae isolates from recent cholera epidemics in the Democratic Republic of the Congo (DRC), Zambia, Guinea and Togo. We aimed to assess the relationship between outbreaks. Applying this method, we identified 89 unique MLVA haplotypes across our isolate collection. MLVA typing revealed the short-term divergence and microevolution of these Vibrio cholerae populations to provide insight into the dynamics of cholera outbreaks in each country. Our analyses also revealed strong geographical clustering. Isolates from the African Great Lakes Region (DRC and Zambia) formed a closely related group, while West African isolates (Togo and Guinea) constituted a separate cluster. At a country-level scale our analyses revealed several distinct MLVA groups, most notably DRC 2011/2012, DRC 2009, Zambia 2012 and Guinea 2012. We also found that certain MLVA types collected in the DRC persisted in the country for several years, occasionally giving rise to expansive epidemics. Finally, we found that the six environmental isolates in our panel were unrelated to the epidemic isolates.

CONCLUSIONS/SIGNIFICANCE

To effectively combat the disease, it is critical to understand the mechanisms of cholera emergence and diffusion in a region-specific manner. Overall, these findings demonstrate the relationship between distinct epidemics in West Africa and the African Great Lakes Region. This study also highlights the importance of monitoring and analyzing Vibrio cholerae isolates.

Global climate anomalies and potential infectious disease risks: 2014-2015

Background: The El Niño/Southern Oscillation (ENSO) is a global climate phenomenon that impacts human infectious disease risk worldwide through droughts, floods, and other climate extremes. Throughout summer and fall 2014 and winter 2015, El Niño Watch, issued by the US National Oceanic and Atmospheric Administration, assessed likely El Niño development during the Northern Hemisphere fall and winter, persisting into spring 2015. Methods: We identified geographic regions where environmental conditions may increase infectious disease transmission if the predicted El Niño occurs using El Niño indicators (Sea Surface Temperature [SST], Outgoing Longwave Radiation [OLR], and rainfall anomalies) and literature review of El Niño-infectious disease associations. Results: SSTs in the equatorial Pacific and western Indian Oceans were anomalously elevated during August-October 2014, consistent with a developing weak El Niño event. Teleconnections with local climate is evident in global precipitation patterns, with positive OLR anomalies (drier than average conditions) across Indonesia and coastal southeast Asia, and negative anomalies across northern China, the western Indian Ocean, central Asia, north-central and northeast Africa, Mexico/Central America, the southwestern United States, and the northeastern and southwestern tropical Pacific. Persistence of these conditions could produce environmental settings conducive to increased transmission of cholera, dengue, malaria, Rift Valley fever, and other infectious diseases in regional hotspots as during previous El Niño events. Discussion and Conclusions: The current development of weak El Niño conditions may have significant potential implications for global public health in winter 2014-spring 2015. Enhanced surveillance and other preparedness measures in predicted infectious disease hotspots could mitigate health impacts.

Interaction between climatic, environmental, and demographic factors on cholera outbreaks in Kenya

BACKGROUND

Cholera remains an important public health concern in developing countries including Kenya where 11,769 cases and 274 deaths were reported in 2009 according to the World Health Organization (WHO). This ecological study investigates the impact of various climatic, environmental, and demographic variables on the spatial distribution of cholera cases in Kenya.

METHODS

District-level data was gathered from Kenya's Division of Disease Surveillance and Response, the Meteorological Department, and the National Bureau of Statistics. The data included the entire population of Kenya from 1999 to 2009.

RESULTS

Multivariate analyses showed that districts had an increased risk of cholera outbreaks when a greater proportion of the population lived more than five kilometers from a health facility (RR: 1.025 per 1% increase; 95% CI: 1.010, 1.039), bordered a body of water (RR: 5.5; 95% CI: 2.472, 12.404), experienced increased rainfall from October to December (RR: 1.003 per 1 mm increase; 95% CI: 1.001, 1.005), and experienced decreased rainfall from April to June (RR: 0.996 per 1 mm increase; 95% CI: 0.992, 0.999). There was no detectable association between cholera and population density, poverty, availability of piped water, waste disposal methods, rainfall from January to March, or rainfall from July to September.

CONCLUSION

Bordering a large body of water, lack of health facilities nearby, and changes in rainfall were significantly associated with an increased risk of cholera in Kenya.

Development of pVCR94ΔX from Vibrio cholerae, a prototype for studying multidrug resistant IncA/C conjugative plasmids

Antibiotic resistance has grown steadily in Vibrio cholerae over the last few decades to become a major threat in countries affected by cholera. Multi-drug resistance (MDR) spreads among clinical and environmental V. cholerae strains by lateral gene transfer often mediated by integrative and conjugative elements (ICEs) of the SXT/R391 family. However, in a few reported but seemingly isolated cases, MDR in V. cholerae was shown to be associated with other self-transmissible genetic elements such as conjugative plasmids. IncA/C conjugative plasmids are often found associated with MDR in isolates of Enterobacteriaceae. To date, IncA/C plasmids have not been commonly found in V. cholerae or other species of Vibrio. Here we present a detailed analysis of pVCR94ΔX derived from pVCR94, a novel IncA/C conjugative plasmid identified in a V. cholerae clinical strain isolated during the 1994 Rwandan cholera outbreak. pVCR94 was found to confer resistance to sulfamethoxazole, trimethoprim, ampicillin, streptomycin, tetracycline, and chloramphenicol and to transfer at very high frequency. Sequence analysis revealed its mosaic nature as well as high similarity of the core genes responsible for transfer and maintenance with other IncA/C plasmids and ICEs of the SXT/R391 family. Although IncA/C plasmids are considered a major threat in antibiotics resistance, their basic biology has received little attention, mostly because of the difficulty to genetically manipulate these MDR conferring elements. Therefore, we developed a convenient derivative from pVCR94, pVCR94Δ X, a 120.5-kb conjugative plasmid which only codes for sulfamethoxazole resistance. Using pVCR94Δ X, we identified the origin of transfer (oriT) and discovered an essential gene for transfer, both located within the shared backbone, allowing for an annotation update of all IncA/C plasmids. pVCR94Δ X may be a useful model that will provide new insights on the basic biology of IncA/C conjugative plasmids.

National surveillance data on the epidemiology of cholera in Kenya, 1997-2010

BACKGROUND

Kenya has experienced multiple cholera outbreaks since 1971. Cholera remains an issue of major public health importance and one of the 35 priority diseases under Kenya's updated Integrated Disease Surveillance and Response strategy.

METHODS

We reviewed the cholera surveillance data reported to the World Health Organization and the Kenya Ministry of Public Health and Sanitation from 1997 through 2010 to determine trends in cholera disease for the 14-year period.

RESULTS

A total of 68 522 clinically suspected cases of cholera and 2641 deaths were reported (overall case-fatality rate [CFR], 3.9%), affecting all regions of the country. Kenya's largest outbreak occurred during 1997-1999, resulting in 26 901 cases and 1362 deaths (CFR, 5.1%). Following a decline in disease occurrence, the country experienced a resurgence of epidemic cholera during 2007-2009 (16 616 cases and 454 deaths; CFR, 2.7%), which declined rapidly to 0 cases. Cases were reported through July 2010, with no cases reported during the second half of the year. About 42% of cases occurred in children aged <15 years. Vibrio cholerae O1, serotype Inaba, was the predominant strain recorded from 2007 through 2010, although serotype Ogawa was also isolated. Recurrent outbreaks have most frequently affected Nairobi, Nyanza, and Coast provinces, as well as remote arid and semiarid regions and refugee camps.

DISCUSSION

Kenya has experienced substantial amounts of reported cases of cholera during the past 14 years. Recent decreases in cholera case counts may reflect cholera control measures put in place by the National Ministry of Health; confirmation of this theory will require ongoing surveillance.

The burden of cholera in Uganda

INTRODUCTION

In 2010, the World Health Organization released a new cholera vaccine position paper, which recommended the use of cholera vaccines in high-risk endemic areas. However, there is a paucity of data on the burden of cholera in endemic countries. This article reviewed available cholera surveillance data from Uganda and assessed the sufficiency of these data to inform country-specific strategies for cholera vaccination.

METHODS

The Uganda Ministry of Health conducts cholera surveillance to guide cholera outbreak control activities. This includes reporting the number of cases based on a standardized clinical definition plus systematic laboratory testing of stool samples from suspected cases at the outset and conclusion of outbreaks. This retrospective study analyzes available data by district and by age to estimate incidence rates. Since surveillance activities focus on more severe hospitalized cases and deaths, a sensitivity analysis was conducted to estimate the number of non-severe cases and unrecognized deaths that may not have been captured.

RESULTS

Cholera affected all ages, but the geographic distribution of the disease was very heterogeneous in Uganda. We estimated that an average of about 11,000 cholera cases occurred in Uganda each year, which led to approximately 61-182 deaths. The majority of these cases (81%) occurred in a relatively small number of districts comprising just 24% of Uganda's total population. These districts included rural areas bordering the Democratic Republic of Congo, South Sudan, and Kenya as well as the slums of Kampala city. When outbreaks occurred, the average duration was about 15 weeks with a range of 4-44 weeks.

DISCUSSION

There is a clear subdivision between high-risk and low-risk districts in Uganda. Vaccination efforts should be focused on the high-risk population. However, enhanced or sentinel surveillance activities should be undertaken to better quantify the endemic disease burden and high-risk populations prior to introducing the vaccine.

Population and genetic study of Vibrio cholerae from the amazon environment confirms that the WASA-1 prophage is the main marker of the epidemic strain that circulated in the region

Vibrio cholerae is a natural inhabitant of many aquatic environments in the world. Biotypes harboring similar virulence-related gene clusters are the causative agents of epidemic cholera, but the majority of strains are harmless to humans. Since 1971, environmental surveillance for potentially pathogenic V. cholerae has resulted in the isolation of many strains from the Brazilian Amazon aquatic ecosystem. Most of these strains are from the non-O1/non-O139 serogroups (NAGs), but toxigenic O1 strains were isolated during the Latin America cholera epidemic in the region (1991-1996). A collection of environmental V. cholerae strains from the Brazilian Amazon belonging to pre-epidemic (1977-1990), epidemic (1991-1996), and post-epidemic (1996-2007) periods in the region, was analyzed. The presence of genes related to virulence within the species and the genetic relationship among the strains were studied. These variables and the information available concerning the strains were used to build a Bayesian multivariate dependency model to distinguish the importance of each variable in determining the others. Some genes related to the epidemic strains were found in environmental NAGs during and after the epidemic. Significant diversity among the virulence-related gene content was observed among O1 strains isolated from the environment during the epidemic period, but not from clinical isolates, which were analyzed as controls. Despite this diversity, these strains exhibited similar PFGE profiles. PFGE profiles were significant while separating potentially epidemic clones from indigenous strains. No significant correlation with isolation source, place or period was observed. The presence of the WASA-1 prophage significantly correlated with serogroups, PFGE profiles, and the presence of virulence-related genes. This study provides a broad characterization of the environmental V. cholerae population from the Amazon, and also highlights the importance of identifying precisely defined genetic markers such as the WASA-1 prophage for the surveillance of cholera.

Comparing sociocultural features of cholera in three endemic African settings

BACKGROUND

Cholera mainly affects developing countries where safe water supply and sanitation infrastructure are often rudimentary. Sub-Saharan Africa is a cholera hotspot. Effective cholera control requires not only a professional assessment, but also consideration of community-based priorities. The present work compares local sociocultural features of endemic cholera in urban and rural sites from three field studies in southeastern Democratic Republic of Congo (SE-DRC), western Kenya and Zanzibar.

METHODS

A vignette-based semistructured interview was used in 2008 in Zanzibar to study sociocultural features of cholera-related illness among 356 men and women from urban and rural communities. Similar cross-sectional surveys were performed in western Kenya (n = 379) and in SE-DRC (n = 360) in 2010. Systematic comparison across all settings considered the following domains: illness identification; perceived seriousness, potential fatality and past household episodes; illness-related experience; meaning; knowledge of prevention; help-seeking behavior; and perceived vulnerability.

RESULTS

Cholera is well known in all three settings and is understood to have a significant impact on people's lives. Its social impact was mainly characterized by financial concerns. Problems with unsafe water, sanitation and dirty environments were the most common perceived causes across settings; nonetheless, non-biomedical explanations were widespread in rural areas of SE-DRC and Zanzibar. Safe food and water and vaccines were prioritized for prevention in SE-DRC. Safe water was prioritized in western Kenya along with sanitation and health education. The latter two were also prioritized in Zanzibar. Use of oral rehydration solutions and rehydration was a top priority everywhere; healthcare facilities were universally reported as a primary source of help. Respondents in SE-DRC and Zanzibar reported cholera as affecting almost everybody without differentiating much for gender, age and class. In contrast, in western Kenya, gender differentiation was pronounced, and children and the poor were regarded as most vulnerable to cholera.

CONCLUSIONS

This comprehensive review identified common and distinctive features of local understandings of cholera. Classical treatment (that is, rehydration) was highlighted as a priority for control in the three African study settings and is likely to be identified in the region beyond. Findings indicate the value of insight from community studies to guide local program planning for cholera control and elimination.

Environmental factors influencing epidemic cholera

Cholera outbreak following the earthquake of 2010 in Haiti has reaffirmed that the disease is a major public health threat. Vibrio cholerae is autochthonous to aquatic environment, hence, it cannot be eradicated but hydroclimatology-based prediction and prevention is an achievable goal. Using data from the 1800s, we describe uniqueness in seasonality and mechanism of occurrence of cholera in the epidemic regions of Asia and Latin America. Epidemic regions are located near regional rivers and are characterized by sporadic outbreaks, which are likely to be initiated during episodes of prevailing warm air temperature with low river flows, creating favorable environmental conditions for growth of cholera bacteria. Heavy rainfall, through inundation or breakdown of sanitary infrastructure, accelerates interaction between contaminated water and human activities, resulting in an epidemic. This causal mechanism is markedly different from endemic cholera where tidal intrusion of seawater carrying bacteria from estuary to inland regions, results in outbreaks.

Molecular characterization of the circulating strains of Vibrio cholerae during 2010 cholera outbreak in Nigeria

This study aimed at characterizing the phenotypic and toxigenic status of circulating strains of cholera during outbreaks in Nigeria, employing molecular typing techniques. Two hundred and one samples of rectal swabs, stool, vomitus, water (from the well, borehole, sachet, stream, and tap) and disinfectants (sodium hypochlorite) were collected from three states in the country. The samples were inoculated on thiosulphate-citrate bile salt-sucrose (TCBS), Cary-Blair transport medium and smeared on glass slides for direct examination. The Vibrio cholerae isolates were serotyped, biotyped, and characterized using PCR of the cytotoxin gene A (ctxA), wbeO1, and wbfO139 gene primer. Of the 201 samples screened, 96 were positive for V cholerae O1 (48%), with 69 (72%) positive for ctxA gene. The results from this study showed that the circulating strains of cholera in Nigeria were of Ogawa serotype, also observed in other outbreaks in Nigeria (1991, 1992, and 1996). However, the strains were of the Classical biotype and were mainly (72%) ctxA gene-positive. This current investigation has confirmed the production of cholera toxin by the circulating strains, and this could be harnessed for possible cholera vaccine production in Nigeria.

Spatio-temporal dynamics of cholera during the first year of the epidemic in Haiti

BACKGROUND

In October 2010, cholera importation in Haiti triggered an epidemic that rapidly proved to be the world's largest epidemic of the seventh cholera pandemic. To establish effective control and elimination policies, strategies rely on the analysis of cholera dynamics. In this report, we describe the spatio-temporal dynamics of cholera and the associated environmental factors.

METHODOLOGY/PRINCIPAL FINDINGS

Cholera-associated morbidity and mortality data were prospectively collected at the commune level according to the World Health Organization standard definition. Attack and mortality rates were estimated and mapped to assess epidemic clusters and trends. The relationships between environmental factors were assessed at the commune level using multivariate analysis. The global attack and mortality rates were 488.9 cases/10,000 inhabitants and 6.24 deaths/10,000 inhabitants, respectively. Attack rates displayed a significantly high level of spatial heterogeneity (varying from 64.7 to 3070.9 per 10,000 inhabitants), thereby suggesting disparate outbreak processes. The epidemic course exhibited two principal outbreaks. The first outbreak (October 16, 2010-January 30, 2011) displayed a centrifugal spread of a damping wave that suddenly emerged from Mirebalais. The second outbreak began at the end of May 2011, concomitant with the onset of the rainy season, and displayed a highly fragmented epidemic pattern. Environmental factors (river and rice fields: p<0.003) played a role in disease dynamics exclusively during the early phases of the epidemic.

CONCLUSION

Our findings demonstrate that the epidemic is still evolving, with a changing transmission pattern as time passes. Such an evolution could have hardly been anticipated, especially in a country struck by cholera for the first time. These results argue for the need for control measures involving intense efforts in rapid and exhaustive case tracking.

Circulation and transmission of clones of Vibrio cholerae during cholera outbreaks

Cholera is still a major public health problem. The underlying bacterial pathogen Vibrio cholerae (V. cholerae) is evolving and some of its mutations have set the stage for outbreaks. After V. cholerae acquired the mobile elements VSP I & II, the El Tor pandemic began and spread across the tropics. The replacement of the O1 serotype encoding genes with the O139 encoding genes triggered an outbreak that swept across the Indian subcontinent. The sxt element generated a third selective sweep and most recently a fourth sweep was associated with the exchange of the El Tor ctx allele for a classical ctx allele in the El Tor background. In Kenya, variants of this fourth selective sweep have differentiated and become endemic residing in and emerging from environmental reservoirs. On a local level, studies in Bangladesh have revealed that outbreaks may arise from a nonrandom subset of the genetic lineages in the environment and as the population of the pathogen expands, many novel mutations may be found increasing the amount of genetic variation, a phenomenon known as a founder flush. In Haiti, after the initial invasion and expansion of V. cholerae in 2010, a second outbreak occurred in the winter of 2011-2012 driven by natural selection of specific mutations.

Molecular epidemiology of geographically dispersed Vibrio cholerae, Kenya, January 2009-May 2010

Isolates represent multiple genetic lineages, a finding consistent with multiple emergences from endemic reservoirs.

Numerous outbreaks of cholera have occurred in Kenya since 1971. To more fully understand the epidemiology of cholera in Kenya, we analyzed the genetic relationships among 170 Vibrio cholerae O1 isolates at 5 loci containing variable tandem repeats. The isolates were collected during January 2009–May 2010 from various geographic areas throughout the country. The isolates grouped genetically into 5 clonal complexes, each comprising a series of genotypes that differed by an allelic change at a single locus. No obvious correlation between the geographic locations of the isolates and their genotypes was observed. Nevertheless, geographic differentiation of the clonal complexes occurred. Our analyses showed that multiple genetic lineages of V. cholerae were simultaneously infecting persons in Kenya. This finding is consistent with the simultaneous emergence of multiple distinct genetic lineages of V. cholerae from endemic environmental reservoirs rather than recent introduction and spread by travelers.

Cholera ante portas - The re-emergence of cholera in Kinshasa after a ten-year hiatus

Background: Cholera is an endemic disease in certain well-defined areas in the east of the Democratic Republic of Congo (DRC). The west of the country, including the mega-city Kinshasa, has been free of cases since mid 2001 when the last outbreak ended. Methods and Findings: We used routinely collected passive surveillance data to construct epidemic curves of the cholera cases and map the spatio-temporal progress of the disease during the first 47 weeks of 2011. We compared the spatial distribution of disease spread to that which occurred in the last cholera epidemic in Kinshasa between 1996 and 2001. To better understand previous determinants of cholera spread in this region, we conducted a correlation analysis to assess the impact of rainfall on weekly health zone cholera case counts between December 1998 and March 2001 and a Generalized Linear Model (GLM) regression analysis to identify factors that have been associated with the most vulnerable health zones within Kinshasa between October 1998 and June 1999. In February 2011, cholera reemerged in a region surrounding Kisangani and gradually spread westwards following the course of the Congo River to Kinshasa, home to 10 million people. Ten sampled isolates were confirmed to be Vibrio cholerae O1, biotype El Tor, serotype Inaba, resistant to trimethoprim-sulfa, furazolidone, nalidixic acid, sulfisoxaole, and streptomycin, and intermediate resistant to Chloramphenicol. An analysis of a previous outbreak in Kinshasa shows that rainfall was correlated with case counts and that health zone population densities as well as fishing and trade activities were predictors of case counts. Conclusion: Cholera is particularly difficult to tackle in the DRC. Given the duration of the rainy season and increased riverine traffic from the eastern provinces in late 2011, we expect further increases in cholera in the coming months and especially within the mega-city Kinshasa. We urge all partners involved in the response to remain alert.

Didier Bompangue and Silvan Vesenbeckh contributed equally to this work. *corresponding author: Silvan Vesenbeckh, Harvard School of Public Health (vesenbeckh@gmail.com)

Didier Bompangue is Associate Professor in the Department of Microbiology (University of Kinshasa) and

Epidemiologist in the DRC Ministry of Health. He was involved in the investigations of the described outbreak since February 2011.