title: Incongruent HIV and tuberculosis co-dynamics in Kenya: interacting epidemics monitor each other.
abstract: OBJECTIVE
  Kenya is heralded as an example of declining HIV in Africa, while its tuberculosis (TB) numbers continue rising. We conducted a comparative investigation of TB-HIV co-dynamics in Africa to determine the likelihood of reported trends.
  
  
  RESULTS
  Our mathematical modeling analysis exposes the notable incongruence of reported trends in Kenya because TB-HIV co-dynamics, tightly knit worldwide and most dramatically in sub-Saharan Africa, suggest that declining HIV trends should trigger reductions in TB trends. Moreover, a continental-scale analysis of TB-HIV trends places Kenya as an outlier in eastern and southern Africa, and shows TB outpacing HIV in western central Africa. We further investigate which TB processes across HIV stages have greater potential to reduce TB incidence via a sensitivity analysis.
  
  
  CONCLUSIONS
  There are two parsimonious explanations: an unaccounted improvement in TB case detection has occurred, or HIV is not declining as reported. The TB-HIV mismatch could be compounded by surveillance biases due to spatial heterogeneity in disease dynamics. Results highlight the need to re-evaluate trends of both diseases in Kenya, and identify the most critical epidemiological factors at play. Substantial demographic changes have occurred in Kenya, including rapid urbanization accompanied by poor living conditions, which could disproportionately increase TB incidence. Other possible contributors include immune reconstitution due to the recent delivery of antiretrovirals, and an increased presence of the virulent Beijing/W TB genotype. Results support the importance of integrating information from closely interacting epidemics, because this approach provides critical insights unobtainable when components of generalized epidemics are considered individually.
authors.affiliation: Department of Environmental Science, Policy and Management, University of California, 137 Mulford Hall, Berkeley, CA 94720-3112, USA. msanchez@nature.berkeley.edu
authors.forename: María S
authors.initials: MS
authors.lastname: Sánchez
authors.forename: James O
authors.initials: JO
authors.lastname: Lloyd-Smith
authors.forename: Brian G
authors.initials: BG
authors.lastname: Williams
authors.forename: Travis C
authors.initials: TC
authors.lastname: Porco
authors.forename: Sadie J
authors.initials: SJ
authors.lastname: Ryan
authors.forename: Martien W
authors.initials: MW
authors.lastname: Borgdorff
authors.forename: John
authors.initials: J
authors.lastname: Mansoer
authors.forename: Christopher
authors.initials: C
authors.lastname: Dye
authors.forename: Wayne M
authors.initials: WM
authors.lastname: Getz
mesh_terms: D044966:Anti-Retroviral Agents / Q000627:therapeutic use; D015658:HIV Infections / Q000188:drug therapy / Q000453:epidemiology*; D006801:Humans; D007630:Kenya / Q000453:epidemiology; D008954:Models, Biological; D015995:Prevalence; D018571:Sentinel Surveillance; D014376:Tuberculosis / Q000175:diagnosis / Q000453:epidemiology* / Q000517:prevention & control
chemical_list: D044966:Anti-Retroviral Agents