Updated estimates of typhoid fever burden in sub-Saharan Africa
Authors: Jong-Hoon Kim, Vittal Mogasale, Justin Im, Enusa Ramani, Florian Marks
Journal: The Lancet Global Health (2017)

The Typhoid Fever Surveillance in Africa Program (TSAP), which was conducted over a 2-year period between 2010 and 2013, provided new incidence figures for typhoid fever in sub-Saharan Africa.1Marks F von Kalckreuth V Aaby P et al.Incidence of invasive salmonella disease in sub-Saharan Africa: a multicentre population-based surveillance study.Lancet Glob Health. 2017; 5: e310-e323Summary Full Text Full Text PDF PubMed Scopus (161) Google Scholar We used these novel data to update estimates of typhoid fever disease burden in Africa according to a model that was previously developed to estimate typhoid fever disease burden in low-income and middle-income countries.2Mogasale V Maskery B Ochiai RL et al.Burden of typhoid fever in low-income and middle-income countries: a systematic, literature-based update with risk-factor adjustment.Lancet Glob Health. 2014; 2: e570-e580Summary Full Text Full Text PDF PubMed Scopus (341) Google Scholar We performed probabilistic multivariate sensitivity analysis to evaluate the uncertainty associated with the updated estimates, with and without correction for water-related risk (table, appendix). These findings were then compared with results from previous studies.2Mogasale V Maskery B Ochiai RL et al.Burden of typhoid fever in low-income and middle-income countries: a systematic, literature-based update with risk-factor adjustment.Lancet Glob Health. 2014; 2: e570-e580Summary Full Text Full Text PDF PubMed Scopus (341) Google Scholar Blood culture sensitivity was assumed to be 61·0% (95% CI 52·0–70·0) based on a systematic literature review.3Mogasale V Ramani E Mogasale VV Park J What proportion of Salmonella Typhi cases are detected by blood culture? a systematic literature review.Ann Clin Microbiol Antimicrob. 2016; 15: 32Crossref PubMed Scopus (66) Google ScholarTableTyphoid fever burden in Africa estimated from 2010 population data2Mogasale V Maskery B Ochiai RL et al.Burden of typhoid fever in low-income and middle-income countries: a systematic, literature-based update with risk-factor adjustment.Lancet Glob Health. 2014; 2: e570-e580Summary Full Text Full Text PDF PubMed Scopus (341) Google ScholarPublished disease burden2Mogasale V Maskery B Ochiai RL et al.Burden of typhoid fever in low-income and middle-income countries: a systematic, literature-based update with risk-factor adjustment.Lancet Glob Health. 2014; 2: e570-e580Summary Full Text Full Text PDF PubMed Scopus (341) Google ScholarUpdated disease burdenAdjusted*Adjusted for water-related risk. LMICs=low-income and middle-income countries.Adjusted*Adjusted for water-related risk. LMICs=low-income and middle-income countries.UnadjustedNorth Africa33 807 (25 809–44 185)33 807 (26 213–44 165)61 971 (50 089–75 713)East Africa1 749 861 (1 386 537–2 203 996)1 136 475 (923 293–1 408 893)1 537 745 (1 260 751–1 859 727)West Africa489 669 (309 531–729 282)1 290 109 (1 033 714–1 609 697)1 720 936 (1 380 325–2 113 584)Middle Africa713 517 (568 060–887 805)713 517 (569 039–889 638)881 368 (704 662–1 091 018)Southern Africa103 542 (76 359–140 868)103 542 (75 835–140 861)188 529 (143 043–244 423)Total for Africa3 090 396 (2 504 427–3 829 277)3 277 450 (2 763 807–3 922 186)4 390 549 (3 741 502–5 141 476)Total for LMICs11 883 047 (9 925 551–14 751 214)12 070 102 (10 013 525–14 827 728)20 811 469 (17 762 215–24 270 115)Data are mean cases (95% CI).* Adjusted for water-related risk. LMICs=low-income and middle-income countries. Open table in a new tab Data are mean cases (95% CI). Of the 13 TSAP sentinel sites, incidence data were available from nine sites representing six countries: Burkina Faso (two sites), Guinea-Bissau, Ghana, Tanzania (two sites), Kenya, and Madagascar (two sites).1Marks F von Kalckreuth V Aaby P et al.Incidence of invasive salmonella disease in sub-Saharan Africa: a multicentre population-based surveillance study.Lancet Glob Health. 2017; 5: e310-e323Summary Full Text Full Text PDF PubMed Scopus (161) Google Scholar The updated mean annual typhoid fever incidence per 100 000 people decreased from 537 to 348 in east Africa and increased from 160 to 422 in west Africa following our analysis (data not shown). These figures correspond to an average annual incidence of 318 per 100 000 people in Africa, which is an increase of 18 per 100 000 from the previous estimates.2Mogasale V Maskery B Ochiai RL et al.Burden of typhoid fever in low-income and middle-income countries: a systematic, literature-based update with risk-factor adjustment.Lancet Glob Health. 2014; 2: e570-e580Summary Full Text Full Text PDF PubMed Scopus (341) Google Scholar Compared with these previously published figures,2Mogasale V Maskery B Ochiai RL et al.Burden of typhoid fever in low-income and middle-income countries: a systematic, literature-based update with risk-factor adjustment.Lancet Glob Health. 2014; 2: e570-e580Summary Full Text Full Text PDF PubMed Scopus (341) Google Scholar the resulting overall burden increased by 6·1% in Africa and 1·6% among all low-income and middle-income countries; however, these differences remain within the 95% CI of the previous estimates.2Mogasale V Maskery B Ochiai RL et al.Burden of typhoid fever in low-income and middle-income countries: a systematic, literature-based update with risk-factor adjustment.Lancet Glob Health. 2014; 2: e570-e580Summary Full Text Full Text PDF PubMed Scopus (341) Google Scholar These changes can be mostly attributed to the increased incidence in Ghana and Burkina Faso, and decreased incidence in Kenya and Madagascar observed through TSAP compared with previous projections. Updated data on the burden of typhoid fever are subject to the same limitations as previous studies.2Mogasale V Maskery B Ochiai RL et al.Burden of typhoid fever in low-income and middle-income countries: a systematic, literature-based update with risk-factor adjustment.Lancet Glob Health. 2014; 2: e570-e580Summary Full Text Full Text PDF PubMed Scopus (341) Google Scholar, 4Crump JA Luby SP Mintz ED The global burden of typhoid fever.Bull World Health Organ. 2004; 82: 346-353PubMed Google Scholar, 5Mogasale V Mogasale VV Ramani E et al.Revisiting typhoid fever surveillance in low and middle income countries: lessons from systematic literature review of population-based longitudinal studies.BMC Infect Dis. 2016; 16: 35Crossref PubMed Scopus (34) Google Scholar Nevertheless, these estimates show that the burden of typhoid fever in Africa continues to be high, and highlight the need for control measures, including typhoid vaccination for high-risk populations and areas, and improvements in water, sanitation, and hygiene. J-HK, VM, JI, ER, and FM are supported by research grants from the Bill & Melinda Gates Foundation (OPPGH5321 and OPP1127988), outside this work. The International Vaccine Institute also received core funding support from the Government of South Korea and the Government of Sweden, outside this work. We declare no other competing interests. Incidence of invasive salmonella disease in sub-Saharan Africa: a multicentre population-based surveillance studyTyphoid fever and iNTS disease are major causes of invasive bacterial febrile illness in the sampled locations, most commonly affecting children in both low and high population density settings. The development of iNTS vaccines and the introduction of S Typhi conjugate vaccines should be considered for high-incidence settings, such as those identified in this study. Full-Text PDF Open Access