decline means that it has been higher than the baseline community risk, and it will not be possible to assume that there is no excess risk until no further decline is observed.

A large portion of the current and recent risk to health care workers of tuberculous infection is the result of exposure to unsuspected cases of infectious tuberculosis or to exposure in circumstances of poor ventilation. In some outbreaks from unsuspected sources, exposed employee infection rates have been as high as 50 percent. When effective infection control procedures are in place, unsuspected contagious cases of tuberculosis may provide nearly all of the occupational tuberculosis risk.

The risk to health care workers of tuberculous infection varies with job category. In general, health care workers in contact with patients are at higher risk than those with no patient contact. Noncontact employees often have a higher incidence of infection than contact employees, but this is due to community exposure risk. Job situations of exceptionally high risk are those involving the generation of respiratory aerosols from patients, including bronchoscopy, endotracheal suctioning and intubation, cough and sputum induction, and the administration of irritation medications (e.g., pentamidine) by aerosol.

The risk to health care workers of tuberculous infection varies in the United States with geographic locale. The incidence of tuberculosis varies greatly with location in the United States. Coastal urban cities bear the greatest tuberculosis burden and rural Midwest and mountain state regions the least. Health care facilities in these various regions care for numbers of patients with tuberculosis that vary substantially in parallel with variations in incidence.

The risk to health care workers of tuberculous infection varies in the United States with demography and ethnicity. In general, individuals of African-American, Hispanic, and Asian heritage have a higher incidence of tuberculous infection than do persons of European extraction. Foreign-born Americans bring with them much of the tuberculous infection risk of the countries of their origins. The risk of tuberculous infection varies greatly with socioeconomic status, most of the infection risk being incurred by those who are less affluent. For health care workers, these variations in population tuberculosis incidence have two important consequences. First of all, the tuberculous infection risk in the community in which health care workers reside and in which they usually spend more time than they do in their job setting is correlated with these ethnic and demographic variables. Second, the population served by the health care facility will influence the amount of potential tuberculosis exposure of the employees.

The occupational tuberculosis risk to American health care workers can be quantified only in approximate terms. The magnitude of the tuberculosis risk to American health care workers at the current time in those



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