Cholera Incidence and Mortality in Sub-Saharan African Sites during Multi-country Surveillance

Abstract

BackgroundCholera burden in Africa remains unknown, often because of weak national surveillance systems. We analyzed data from the African Cholera Surveillance Network (www.africhol.org).Methods/ Principal findingsDuring June 2011–December 2013, we conducted enhanced surveillance in seven zones and four outbreak sites in Togo, the Democratic Republic of Congo (DRC), Guinea, Uganda, Mozambique and Cote d’Ivoire. All health facilities treating cholera cases were included. Cholera incidences were calculated using culture-confirmed cholera cases and culture-confirmed cholera cases corrected for lack of culture testing usually due to overwhelmed health systems and imperfect test sensitivity. Of 13,377 reported suspected cases, 34% occurred in Conakry, Guinea, 47% in Goma, DRC, and 19% in the remaining sites. From 0–40% of suspected cases were aged under five years and from 0.3–86% had rice water stools. Within surveillance zones, 0–37% of suspected cases had confirmed cholera compared to 27–38% during outbreaks. Annual confirmed incidence per 10,000 population was <0.5 in surveillance zones, except Goma where it was 4.6. Goma and Conakry had corrected incidences of 20.2 and 5.8 respectively, while the other zones a median of 0.3. During outbreaks, corrected incidence varied from 2.6 to 13.0. Case fatality ratios ranged from 0–10% (median, 1%) by country.Conclusions/SignificanceAcross different African epidemiological contexts, substantial variation occurred in cholera incidence, age distribution, clinical presentation, culture confirmation, and testing frequency. These results can help guide preventive activities, including vaccine use.

Epidemiology of cholera outbreaks and socio-economic characteristics of the communities in the fishing villages of Uganda: 2011-2015

“…The CFRs were higher than those recommended by WHO but similar to those documented at country-wide levels (2.4% vs 1.6–2.2%) [11] and to what was seen through the AFRICHOL enhanced surveillance in specific zones of Uganda (2.5%, mainly Kasese and Mbale districts) [20]. The CFR was 2.5-fold higher among males than females possibly because males fell ill while on the lakes fishing and in places distant from treatment facilities.…”

“…In addition to the routine MOH disease surveillance system, Uganda with other eight (8) sub-Saharan African countries participated in the African Cholera Surveillance Network ( AFRICHOL ) project which carried out cholera case-based surveillance in selected surveillance areas [20]. In Uganda, these areas included Kasese district in Western Uganda plus Mbale, Busia, Manafwa, Butaleja and Tororo districts in Eastern Uganda.…”

Multi-site cholera surveillance within the African Cholera Surveillance Network shows endemicity in Mozambique, 2011–2015

“…Incidence of suspected cases varied widely between sites and between years within the same site. The incidence based on suspected cases only may be overestimated, given the low culture confirmation rate, as was shown previously in other Africhol countries [ 9 ].…”

“…Only 52.2% of suspected cases were tested and 23.5% were microbiologically confirmed. This limited capacity to confirm cases by culture combined with limited sensitivity of culture lowered the overall sensitivity of our surveillance [ 9 ]. Our diagnostic procedures relied exclusively upon culture results, which can be influenced by various factors including collection, transport and storage conditions, training of human resources or previous antibiotic exposure.…”

“…Cholera in Mozambique is an endemic disease with seasonal epidemic peaks. The usual cholera season is between January and March with annual incidences ranging from 0 to 211 per 100,000 population with periodically high case-fatality ratios (CFRs) [ 5 – 9 ].…”