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

Abstract

Background: Cholera 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 findings: During 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/significance: Across 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.

Fig 1. Suspect cases with culture done and Suspect cases with positive culture for Vibrio cholera (first part).

Surveillance zone, Beira city, Mozambique (A); surveillance zone, Koumassi-Vridi-Port Boët district, Abidjan, Cote d’Ivoire (B); surveillance zone, Lake district, Togo (C); surveillance zone, Mbale-Manafwa-Butaleja districts, Uganda (D); surveillance zone, Lome-Golfe districts, Togo (E); surveillance zone, Conakry, Guinea (F); Dark blue bars show cases with culture test done, light blue bars show cases with culture test not done, green bars show cases with Vibrio cholera identified by culture, and yellow bars show cases having a culture negative for Vibrio cholera. The dashed line shows the first month of the enhanced Africhol surveillance. The dotted line shows the last month of the enhanced Africhol surveillance.

Fig 2. Suspect cases with culture done and Suspect cases with positive culture for Vibrio cholera (second part).

Surveillance zone, Goma-Karisimbi districts, DRC (G); outbreak site, Pemba city, Mozambique (H); outbreak site, Adiake prefecture, Cote d’Ivoire (I); outbreak site, Kasese district, Uganda (J); outbreak site, Maluku-Kingabwa-Massina districts, Kinshasa, DRC (K). Dark blue bars show cases with culture test done, light blue bars show cases with culture test not done, green bars show cases with Vibrio cholera identified by culture, and yellow bars show cases having a culture negative for Vibrio cholera. The dashed line shows the first month of the enhanced Africhol surveillance. The dotted line shows the last month of the enhanced Africhol surveillance.