
Full text loading...
Category: Clinical Microbiology; Bacterial Pathogenesis
Epidemiology and Host Factors, Page 1 of 2
< Previous page | Next page > /docserver/preview/fulltext/10.1128/9781555817138/9781555815134_Chap02-1.gif /docserver/preview/fulltext/10.1128/9781555817138/9781555815134_Chap02-2.gifAbstract:
The history of tuberculosis in Europe and North America is better known for the past 150 years; however, there is a paucity of historic information on the epidemiology of tuberculosis in other parts of the world. The waveform of the tuberculosis epidemic occurs by natural selection of susceptible persons and runs its course in about 300 years. Industrialization and overcrowding of the cities can produce an epidemic of tuberculosis by bringing together large numbers of susceptible people and promoting transmission of Mycobacterium tuberculosis to new hosts. Although tuberculosis can affect any organ of the body, the lungs are virtually always the portal of entry. Infection with tubercle bacilli evokes cell mediated immunity (CMI) 2 to 8 weeks after infection. Activated T lymphocytes and macrophages form granulomas. Granulomas inhibit replication and spread of organisms. The chapter discusses various factors that may influence the risk of developing tuberculosis in an individual or a population. Utilizing a new molecular epidemiology technique of restriction fragment length polymorphism (RFLP) showed that 40% of cases were due to recent transmission rather than reactivation of previously acquired infection. With advancement in immunology and genomics, T- cell-based in vitro assays of interferon released by T cells after stimulation with M. tuberculosis antigens have been developed to identify tuberculosis infection. Tuberculin testing is most effective in detecting infection among the close contacts of newly diagnosed patients. Further, the chapter talks about special-high risk factors.
Full text loading...
Theoretical concept of the development of tuberculosis (TB) in a community. Tuberculosis is assumed to appear for the first time at zero. The death rate, rate of morbidity, and rate of contacts are shown in reference to a living population. All these curves show a steep ascending limb and a prolonged exponentially decelerated descending limb. (Adapted from reference 57 with permission of the American Thoracic Society.)
Rate of tuberculosis (TB) mortality, morbidity, and contacts at two extreme theoretical urban and rural settings. These two imaginary communities are assumed to remain isolated from the rest of the world. The variation in death rates between countries or communities can be explained by the difference in urbanization, both in time and in space. (From reference 57 with permission of the American Thoracic Society.)
Tuberculosis (TB) mortality rates per 100,000 persons in the United States. SM, streptomycin. (Adapted from reference 93 with permission.)
Major factors that determine transmission of infection from a source case to contacts and natural history of tuberculosis in infected contacts.
Tuberculosis mortality by age and sex—a theoretical presentation. A, period at height of epidemic; B, period at intermediate state; C, period at end of wave. (Adapted from reference 57 with permission of the American Thoracic Society.)
Tuberculosis (TB) case rates by age group and sex, United States, 2008. Rates tended to increase with age. The rates in men 45 years or older were approximately twice those in women of the same age. (Reprinted from reference 35 with permission of the CDC.)
Tuberculosis cases, United States, 1982 to 2008, reported by the National Tuberculosis Surveillance System ( 35 ) (prepared by the Division of Tuberculosis Elimination, CDC). The resurgence of tuberculosis in the mid-1980s peaked in 1992. Cases started declining from 1993 to 2008 (12,904 cases), approximately 50% from 1992.
Estimated HIV coinfections in person reported with tuberculosis, 1993 to 2008. For all ages the estimated rate of coinfection of HIV and TB decreased from 15 to 6% overall; the rate decreased from 29 to 10% in persons aged 25 to 44 years during this period. (Reprinted from reference 35 with permission of the CDC.)
Tuberculosis cases by race/ethnicity in the United States, 2008. A total of 83% of reported cases occurred in racial ethnic minorities, whereas 17% of cases occurred in non-Hispanic whites. Hispanics are the largest group. (Reprinted from reference 35 with permission of the CDC.)
Number of tuberculosis cases in U.S.-born versus foreign-born people, United States, 1993 to 2008. The percentage of cases increased from 29% in 1993 to 59% in 2008. Overall, the number of cases in foreign-born persons remained virtually level (7,000 to 8,000) each year, whereas the number in U.S.-born persons decreased from 17,000 in 1993 to less than 5,300 in 2008. (Reprinted from reference 35 with permission of the CDC.)
Reported cases of tuberculosis by anatomic site. (Reprinted from reference 92a with permission of McGraw-Hill.)
Countries of birth for foreign-born persons reported with tuberculosis in the United States, 2008. (Reprinted from reference 35 with permission of the CDC.)
Trends in tuberculosis cases in foreign-born persons, 1988 to 2008. The number of cases among foreign-born persons increased from nearly 5,000 in 1998 to 7,000 to 8,000 each year since 1991. The percentage of tuberculosis cases accounted for by foreign-born persons increased from 22% in 1988 to 59% in 2008. (Reprinted from reference 35 with permission of the CDC.)
Trends in advanced pulmonary tuberculosis (APT) adjusted for selected risk factors, 1993 to 2006. Bars, APT; squares, age adjusted; triangles, foreign-born adjusted; circles, HIV adjusted; line, unadjusted. (Reprinted from reference 110 with permission.)
Incidence of active tuberculosis in persons with a positive tuberculin test by selected risk factors a
Relative risk for developing active tuberculosis by selected clinical conditions a
Risk factors for TST conversion in Canadian hospitals a