BackgroundThe eastern provinces of the Democratic Republic of the Congo have been identified as endemic areas for cholera transmission, and despite continuous control efforts, they continue to experience regular cholera outbreaks that occasionally spread to the rest of the country. In a region where access to improved water sources is particularly poor, the question of which improvements in water access should be prioritized to address cholera transmission remains unresolved. This study aimed at investigating the temporal association between water supply interruptions and Cholera Treatment Centre (CTC) admissions in a medium-sized town.Methods and FindingsTime-series patterns of daily incidence of suspected cholera cases admitted to the Cholera Treatment Centre in Uvira in South Kivu Province between 2009 and 2014 were examined in relation to the daily variations in volume of water supplied by the town water treatment plant. Quasi-poisson regression and distributed lag nonlinear models up to 12 d were used, adjusting for daily precipitation rates, day of the week, and seasonal variations. A total of 5,745 patients over 5 y of age with acute watery diarrhoea symptoms were admitted to the CTC over the study period of 1,946 d. Following a day without tap water supply, the suspected cholera incidence rate increased on average by 155% over the next 12 d, corresponding to a rate ratio of 2.55 (95% CI: 1.54–4.24), compared to the incidence experienced after a day with optimal production (defined as the 95th percentile—4,794 m3). Suspected cholera cases attributable to a suboptimal tap water supply reached 23.2% of total admissions (95% CI 11.4%–33.2%). Although generally reporting less admissions to the CTC, neighbourhoods with a higher consumption of tap water were more affected by water supply interruptions, with a rate ratio of 3.71 (95% CI: 1.91–7.20) and an attributable fraction of cases of 31.4% (95% CI: 17.3%–42.5%). The analysis did not suggest any association between levels of residual chlorine in the water fed to the distribution network and suspected cholera incidence. Laboratory confirmation of cholera was not available for this analysis.ConclusionsA clear association is observed between reduced availability of tap water and increased incidence of suspected cholera in the entire town of Uvira in Eastern Democratic Republic of the Congo. Even though access to piped water supplies is low in Uvira, improving the reliability of tap water supply may substantially reduce the incidence of suspected cholera, in particular in neighbourhoods having a higher access to tap water. These results argue in favour of water supply investments that focus on the delivery of a reliable and sustainable water supply, and not only on point-of-use water quality improvements, as is often seen during cholera outbreaks.

We evaluated published and unpublished data on cholera cases and deaths reported from clinical care facilities in the 56 health districts of the Democratic Republic of Congo to the National Ministry of Health during 2000-2011. Cholera incidence was highest in the eastern provinces bordering lakes and epidemics primarily originated in this region. Along with a strong seasonal component, our data suggest a potential Vibrio cholerae reservoir in the Rift Valley lakes and the possible contribution of the lakes' fishing industry to the spread of cholera. The National Ministry of Health has committed to the elimination-rather than control-of cholera in DRC and has adopted a new national policy built on improved alert, response, case management, and prevention. To achieve this goal and implement all these measures it will require strong partners in the international community with a similar vision.

IntroductionCholera is endemic in the Eastern provinces of the Democratic Republic of the Congo since 1978, and Uvira in South-Kivu has been reporting suspected cholera cases nearly every week for over a decade. The clinical case definition for suspected cholera is relatively non-specific, and cases are rarely confirmed by laboratory methods, especially in endemic settings. This may lead to over-estimation of cholera cases and limit effective public health responses.Methods and resultsBetween April 2016 and November 2017, 69% of the 2,059 patients admitted to the Uvira Cholera Treatment Centre (CTC) were tested for cholera with rapid diagnostic tests (RDTs). Of those admitted as suspected cholera cases, only 40% tested positive for cholera, equivalent to an estimated annual incidence of suspected/confirmed cholera in Uvira of 43.8 and 16.3 cases per 10,000 inhabitants respectively. A multivariable logistic regression indicates that boys aged 2 to 4 years, girls aged 5 to 15 years and adult men are respectively 1.9, 2.1 and 1.8 times more likely to test positive than adult women. On the contrary, boys under 2 are 10 times less likely to test positive. The odds of testing positive also increase as weekly admissions to the CTC rise, with up to a 5-fold increase observed during the weeks with the highest numbers of admissions compared to the lowest ones. Other predictors of cholera confirmation include duration of stay at the CTC, clinical outcome of admission, lower weekly rainfall and area of residence in Uvira, with the northern part of town having the highest confirmation rate.ConclusionCholera is an on-going public health problem in Uvira but the majority of suspected cases admitted to the CTC were found to be negative for cholera after RDT testing. These findings may have important implications for cholera control strategies in favour of interventions that address cholera and other diarrhoeal diseases alike.

Background Cholera remains a major global health challenge. Uvira, in the Democratic Republic of the Congo (DRC), has had endemic cholera since the 1970’s and has been implicated as a possible point of origin for national outbreaks. A previous study among this population, reported a case confirmation rate of 40% by rapid diagnostic test (RDT) among patients at the Uvira Cholera Treatment Centre (CTC). This study considers the prevalence and diversity of 15 enteric pathogens in suspected cholera cases seeking treatment at the Uvira CTC. Methods We used the Luminex xTAG® multiplex PCR to test for 15 enteric pathogens, including toxigenic strains of V. cholerae in rectal swabs preserved on Whatman FTA Elute cards. Results were interpreted on MAGPIX® and analyzed on the xTAG® Data Analysis Software. Prevalence of enteric pathogens were calculated and pathogen diversity was modelled with a Poisson regression. Results Among 269 enrolled CTC patients, PCR detected the presence of toxigenic Vibrio cholerae in 38% (103/269) of the patients, which were considered to be cholera cases. These strains were detected as the sole pathogen in 36% (37/103) of these cases. Almost half (45%) of all study participants carried multiple enteric pathogens (two or more). Enterotoxigenic Escherichia coli (36%) and Cryptosporidium (28%) were the other most common pathogens identified amongst all participants. No pathogen was detected in 16.4% of study participants. Mean number of pathogens was highest amongst boys and girls aged 1–15 years and lowest in women aged 16–81 years. Ninety-three percent of toxigenic V. cholerae strains detected by PCR were found in patients having tested positive for V. cholerae O1 by RDT. Conclusions Our study supports previous results from DRC and other cholera endemic areas in sub-Sahara Africa with less than half of CTC admissions positive for cholera by PCR. More research is required to determine the causes of severe acute diarrhea in these low-resource, endemic areas to optimize treatment measures. Trial registration This study is part of the impact evaluation study entitled: “Impact Evaluation of Urban Water Supply Improvements on Cholera and Other Diarrheal Diseases in Uvira, Democratic Republic of Congo” registered on 10 October 2016 at clinicaltrials.gov Identification number: NCT02928341.

C holera is an acute life-threatening diarrheal disease responsible for ≈4.3 million cases and 142,000 deaths annually worldwide (1). Excluding epidemic peaks in Haiti and Yemen (2,3), most cases of cholera originate from sub-Saharan Africa, predominantly the African Great Lakes Region (AGLR); specifically, the countries of the Lake Tanganyika basin (4). Many recurrent cholera outbreaks in the Democratic Republic of the Congo (DRC), Tanzania, Burundi, and Zambia have been linked to a common hotspot area around the Lake Tanganyika basin (5-8).By the end of 2018, the World Health Organization had noted a steady decline in cholera cases throughout the world, including the AGLR (9). Continuous genomic surveillance of circulating Vibrio cholerae bacteria strains is required to understand the transmission dynamics and genetic evolution of V. cholerae and potentially to guide prevention and response interventions to continue the trend toward decreasing case numbers, in line with the global cholera roadmap to 2030 (10). One lineage, seventh pandemic V. cholerae O1 El Tor (7PET), is responsible for the current pandemic, which began in 1961 (11); Africa was hit by 7PET in 1970 (11). During 1970-2014, >11 different 7PET sublineages were introduced from South Asia into Africa, and sublineage AFR10 (previously T10) replaced AFR5 (previously T5) in the AGLR in the late 1990s (11). Sublineage AFR13 (previously T13) was identified in East Africa (Tanzania, Uganda, Kenya) and Zimbabwe (12). We tracked the 7PET populations circulating in the Lake Tanganyika basin by studying recent V. cholerae O1 isolates collected in the region by conventional bacteriology and genomics and placing these genomes in a broader phylogenetic context to elucidate their evolutionary history. The StudyWe analyzed 96 V. cholerae O1 isolates collected during 2015-2020 in DRC (86 clinical isolates, including 39 collected in 2018-2020) and Tanzania (10 environmental isolates from fish and lake water) (Appendix 1, https://wwwnc.cdc.gov/EID/article/29/1/22-0641-App1.pdf; Appendix 2 Table 1, https://wwwnc. cdc.gov/EID/article/29/1/22-0641-App2.xlsx). We subjected the isolates to antimicrobial susceptibility testing, whole-genome sequencing, genomic characterization, and phylogenetic analyses, as previously Genomic Microevolution ofVibrio cholerae O1,