title: HIV infection and silicosis: the impact of two potent risk factors on the incidence of mycobacterial disease in South African miners.
abstract: OBJECTIVE
  To investigate the combined effects of HIV infection and silicosis on mycobacterial disease.
  
  
  METHODS
  A retrospective cohort of 1374 HIV-positive and 2648 HIV-negative miners who attended a South African gold mining hospital and primary health clinics.
  
  
  METHODS
  Miners who had been tested for HIV, with consent, at primary health clinics during 1991-1996, predominantly because of a symptomatic sexually transmitted disease.
  
  
  RESULTS
  Tuberculosis (TB) incidence was 4.9 and 1.1 per 100 person-years in HIV-positive and HIV-negative miners respectively. The incidence of Mycobacterium kansasii disease was also high (0.32 and 0.10 per 100 person-years, respectively). Silicosis was highly prevalent, implying inadequate dust control, and was a significant TB risk factor among both HIV-positive and HIV-negative men (adjusted incidence rate ratios 1.4-2.5 according to radiological severity). The data were consistent with the risks of silicosis and HIV combining multiplicatively, but did not fit an additive model. The incidence of HIV-associated TB increased significantly during the study, with no corresponding change in HIV-negative rates, to reach 16.1 per 100 person-years among HIV-positive silicotics.
  
  
  CONCLUSIONS
  The risks of silicosis and HIV infection combine multiplicatively, so that TB remains as much a silica-related occupational disease in HIV-positive as in HIV-negative miners, and HIV-positive silicotics have considerably higher TB incidence rates than those reported from other HIV-positive Africans. The increasing impact of HIV over time may indicate epidemic TB transmission with rapid disease development in HIV-infected miners. Similar but currently unrecognized interactions may be contributing to TB control problems in other industrializing countries affected by the HIV epidemic.
authors: Department of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, UK. elizabeth.corbett@lshtm.ac.uk
authors: E L
authors: EL
authors: Corbett
authors: G J
authors: GJ
authors: Churchyard
authors: T C
authors: TC
authors: Clayton
authors: B G
authors: BG
authors: Williams
authors: D
authors: D
authors: Mulder
authors: R J
authors: RJ
authors: Hayes
authors: K M
authors: KM
authors: De Cock
mesh_terms: D017088:AIDS-Related Opportunistic Infections / Q000150:complications / Q000453:epidemiology; D000293:Adolescent; D000328:Adult; D015331:Cohort Studies; D006046:Gold; D015658:HIV Infections / Q000150:complications*; D006679:HIV Seropositivity / Q000150:complications; D006801:Humans; D015994:Incidence; D008297:Male; D008875:Middle Aged; D008906:Mining; D009164:Mycobacterium Infections / Q000150:complications* / Q000453:epidemiology*; D009165:Mycobacterium Infections, Nontuberculous / Q000150:complications / Q000453:epidemiology; D015995:Prevalence; D012189:Retrospective Studies; D012307:Risk Factors; D012829:Silicosis / Q000150:complications* / Q000453:epidemiology; D013019:South Africa / Q000453:epidemiology; D013997:Time Factors; D014376:Tuberculosis / Q000150:complications / Q000453:epidemiology
chemical_list: D006046:Gold