Annual Tuberculosis Incidence Research Articles

Effects of smoking and solid-fuel use on COPD, lung cancer, and tuberculosis in China: a time-based, multiple risk factor, modelling study

SummaryBackgroundChronic obstructive pulmonary disease (COPD), lung cancer, and tuberculosis are three leading causes of death in China, where prevalences of smoking and solid-fuel use are also high. We aimed to predict the effects of risk-factor trends on COPD, lung cancer, and tuberculosis.MethodsWe used representative data sources to estimate past trends in smoking and household solid-fuel use and to construct a range of future scenarios. We obtained the aetiological effects of risk factors on diseases from meta-analyses of epidemiological studies and from large studies in China. We modelled future COPD and lung cancer mortality and tuberculosis incidence, taking into account the accumulation of hazardous effects of risk factors on COPD and lung cancer over time, and dependency of the risk of tuberculosis infection on the prevalence of disease. We quantified the sensitivity of our results to methods and data choices.FindingsIf smoking and solid-fuel use remain at current levels between 2003 and 2033, 65 million deaths from COPD and 18 million deaths from lung cancer are predicted in China; 82% of COPD deaths and 75% of lung cancer deaths will be attributable to the combined effects of smoking and solid-fuel use. Complete gradual cessation of smoking and solid-fuel use by 2033 could avoid 26 million deaths from COPD and 6·3 million deaths from lung cancer; interventions of intermediate magnitude would reduce deaths by 6–31% (COPD) and 8–26% (lung cancer). Complete cessation of smoking and solid-fuel use by 2033 would reduce the projected annual tuberculosis incidence in 2033 by 14–52% if 80% DOTS coverage is sustained, 27–62% if 50% coverage is sustained, or 33–71% if 20% coverage is sustained.InterpretationReducing smoking and solid-fuel use can substantially lower predictions of COPD and lung cancer burden and would contribute to effective tuberculosis control in China.FundingInternational Union Against Tuberculosis and Lung Disease.

Cambios del patrón de enfermedad en la postransición epidemiológica en salud en Chile, 1950-2003

During the twentieth century there was a change in the pattern of diseases in Europe, with an increase in the incidence of allergies and autoimmune disorders, that paralleled a decrease of infectious conditions. The Hygiene hypothesis proposes that these phenomena are causally related. To evaluate the epidemiological changes of allergic, autoimmune, and infectious diseases in Chile between 1950 and 2003. Search for the incidence and prevalence of these diseases in the national records published by the Ministry of Health, as well as through a systematic search of national literature using PubMed and Scielo as search engines. The annual incidence of tuberculosis, rheumatic fever, measles, and typhoid fever has progressively diminished in Chile since 1970. Figures for the national prevalence for asthma, rheumatoid arthritis, and type I diabetes are scarce and difficult to compare, but clearly show an increasing epidemiological trend in the last 20 years. The national figures suggest that, although the country has only recently gone through an epidemiological transition in health problems, there are detectable changes that show the same trends described in Europe.

High risk of tuberculosis in systemic lupus erythematosus?

The incidence and severity of tuberculosis (TB) in patients with systemic lupus erythematosus (SLE) varies greatly among different series. In addition, prospective data are scarce. The aim of this study is to analyse the frequency and severity of TB in our cohort of lupus patients. We analysed data from a prospective database of a single center cohort of 232 patients with SLE (ACR criteria). Prophylaxis with isoniazid was not regularly administered. We identified all cases of TB diagnosed during 10 years (January 1994 to December 2003). The following variables were analysed: annual incidence of TB, location of infection and response to therapy. Data from published series reporting on the incidence of TB among SLE patients were extracted. Three patients (1.3%) suffered clinically manifest TB in 1603 patient-years of follow-up, resulting in an incidence of 187 cases/100,000 patient-years (95% CI 39-547). The pooled annual incidence of TB infection in our area during this period was 30/100,000 individuals. We recorded two cases of pulmonary TB and one case of tuberculous pleurisy. All patients had good response to therapy. The annual incidence of TB among SLE patients in other series, most of them from developing countries, varied between 150/100,000 patients in Turkey and 2450/100,000 patients in India. Of note, high prevalence of extrapulmonary forms as well as elevated TB-associated mortality was reported in most series. TB was more frequent in SLE patients than expected in the general population. We did not see any cases of disseminated infection and all patients had good response to treatment. Our data compare favourably in terms of incidence, severity and outcome with those from highly endemic areas.

The potential impact of enhanced diagnostic techniques for tuberculosis driven by HIV: a mathematical model

To explore the potential impact of enhanced tuberculosis (TB) diagnostic techniques as a TB control strategy in an adult population with high HIV prevalence. A compartmental difference-equation model of TB/HIV was developed using parameter estimates from the literature. The impact of five TB control interventions (rapid molecular testing, mycobacterial culture, community-wide and HIV-targeted active case finding, and highly active antiretroviral therapy) on TB incidence, prevalence, and mortality was modeled in a steady-state population with an HIV prevalence of 17% and annual TB incidence of 409 per 100 000. Sensitivity analyses assessed the influence of each model parameter on the interventions' mortality impact. Enhanced diagnostic techniques (rapid molecular testing or culture) are each projected to reduce TB prevalence and mortality by 20% or more, an impact similar to that of active case-finding in 33% of the general community and greater than the effect achievable by case-finding or antiretroviral treatment efforts in HIV-positive patients alone. The projected impact of enhanced diagnostics on TB incidence (< 10% reduction) is smaller. The impact of TB diagnostics is sensitive to the quality of existing diagnostic standards and the level of access to diagnostic services, but is robust across a wide range of population parameters including HIV and TB incidence. Enhanced TB diagnostic techniques may have substantial impact on TB morbidity and mortality in HIV-endemic regions. As TB rates continue to increase in these areas, enhanced diagnostic techniques merit further consideration as TB control strategies.

BCG in Finland: changing from a universal to a selected programme

In Finland, all newborns are currently offered BCG vaccination, and the national coverage is over 98%. The annual incidence of tuberculosis is low, at 6.6/100,000 in 2004 and has been steadily declining in recent years. Finland differs from the other Nordic countries in that the majority of cases are detected in people aged 65 and over in the indigenous population, and only a smaller proportion (12%) detected in immigrants. The high incidence of TB and MDR TB in neighbouring countries has raised concern, but no increase in TB detected in Finnish-born citizens has been seen. A decision has been made to change from mass BCG vaccination to targeting risk groups.

Risk of Active Tuberculosis Among Schoolchildren in Hong Kong

To estimate the risk of active tuberculosis (TB) and its implication on preventive treatment among BCG-vaccinated schoolchildren. Cohort and case-control designs. Community settings in a high-prevalence area. Children in primary school. The main exposure was their tuberculin response. Of 94,928 primary schoolchildren tuberculin tested during a routine school revaccination program in 1999, 656 with a tuberculin response at 20 mm or more were followed up prospectively through the territory-wide TB registry up to December 31, 2003, for the development of TB. In a separate case-control analysis, the tuberculin responses of children who subsequently had active TB (at the age of 10-15 years) were compared with those of their sex- and age-matched classmates to ascertain the relative risks of TB for different tuberculin reaction categories. The absolute and relative risks were applied to the 1999 cohort for estimating the incidence of TB among different tuberculin reactors. The annual incidence (95% confidence interval) of active TB was estimated to be 13.4 (5.6-40.6) per 100,000 for the entire cohort and 7.5 (2.4-24.5), 7.5 (1.7-32.0), 16.0 (4.4-57.2), 92.6 (26.6-320.2), and 340.6 (163.3-626.4) per 100,000 for children with a tuberculin reaction at 0 to 4, 5 to 9, 10 to 14, 15 to 19, and 20 mm or more, respectively. By using 10 mm as the cutoff, 482 (95% confidence interval, 163-1391) children have to be treated to prevent a single case of active TB within 5 years. Treatment will cover 17.5% of the cohort, but prevent only 54.1% of all active TB cases. It is desirable to reexamine the existing screening method for BCG-vaccinated children from high-prevalence countries.

The Development and Impact of Tuberculosis Vaccines

Vaccination is expected to make a major contribution to the goal of eliminating tuberculosis worldwide by 2050. But developing a new effective vaccine will require innovation in scientific research, a proactive approach to clinical trials of new vaccine candidates, and application of vaccines as part of an integrated approach to disease control.

Official Japanese guidelines for the use of infliximab for rheumatoid arthritis

Differences in ethnic backgrounds as well as in medical and socioeconomic status often affect both the efficacy and adverse effects of medications. Recent data suggest an increased risk of opportunistic infections, especially tuberculosis (TB), among rheumatoid arthritis (RA) patients receiving infliximab, a chimeric monoclonal anti-tumor necrosis factor alpha (TNF-alpha) antibody. In this regard, the annual incidence of TB is approximately five times higher in Japan than in the United States. Furthermore, since Bacillus Calmette-Guérin vaccination is mandatory in childhood when the skin test for purified protein derivative (PPD) is negative, a high incidence of false-positive PPD skin tests is observed among the Japanese population. In addition, the upper limit of methotrexate dosage to be used for RA is lower in Japan. We have therefore established official guidelines for the proper use of infliximab in Japanese RA patients. In this review, an algorithm for the diagnosis and management of TB in RA is presented in an evidenced-based form.

Tubercular Posterior Uveitis

International Ophthalmology Clinics: Spring 2005 - Volume 45 - Issue 2 - p 71-88 doi: 10.1097/01.iio.0000155934.52589.e3

The challenge of diagnosing tuberculosis in children: a perspective from a high incidence area.

Tuberculosis (TB) is a common disease in children living in the developing world. It is estimated that 95% of the 1.4 million childhood TB cases and 450.000 deaths occur in the developing world. It is in these resource-poor countries that the diagnosis is extremely challenging. This article will review some of the difficulties in diagnosing intrathoracic TB in children living in these parts of the world. Children live in communities where the reported annual incidence of TB can be as high as 1297 cases/100.000 population/annum with certain areas in such a community having a reported incidence of greater than 3000 cases/100.000 population/annum. 1 It is not surprising that children living in these communities have an annual risk of TB infection of 3.5%. 2 In low incidence areas children make up a small portion (2 to 5%) of the caseload. In high incidence areas children can contribute up to 39% of the annual caseload 3 and have a notification rate of 3.5-fold greater than that of adults. 3 In these communities it is mostly young children who are infected and develop disease with 79% of the children in this community that develop disease being younger than 5 years. 3 It is generally accepted that most transmission takes place within a household. When a child is infected the index case is usually a household member or close family friend. In communities with a low incidence of TB the presence of a newly diagnosed adult case of TB is an important clue to the diagnosis of TB in a child. In a community with a high TB incidence this seems to be more complex. In a provisional report evaluating the transmission of TB to children using

Local problems, local solutions: improving tuberculosis control at the district level in Malawi.

To examine the causes of a low cure rate at the district level of a tuberculosis (TB) control programme and to formulate, implement, and evaluate an intervention to improve the situation. The study setting was Mzuzu (population 60,000), where the annual smear-positive pulmonary TB incidence was 160 per 100,000 and the human immunodeficiency virus (HIV) seroprevalence was 67% among TB patients. There is one TB treatment unit, but several other organizations are involved with TB control. An examination of case-holding activities was carried out, potential areas for improvement were identified, and interventions performed. In 1990-91, the cure rate was 24% among smear-positive cases (29% among survivors to end of treatment). Problems identified included a fragmented TB control programme; inadequate training and supervision; suboptimal recording of patients' addresses; and nonadherence to national TB control programme protocols. These problems were addressed, and in 1992-93 the cure rate rose to 68% (relative risk (RR) = 2.85 (95% confidence interval (CI) = 1.63, 4.96)) and to 92% among survivors to the end of treatment (RR = 3.12 (95% CI = 1.84, 5.29)). High cure rates are therefore achievable despite high HIV prevalence. Simple, inexpensive, local programmatic interventions can dramatically improve TB case holding. This study demonstrates the need for evaluation, training, and supervision at all levels of the programme.

The Mumbai experience in building field level partnerships for DOTS implementation

In February 1999, the Revised National Tuberculosis (TB) Control Programme (RNTCP) was implemented in the city of Mumbai after a pilot phase of 5 years. The city has a population of more than 12 million people and an estimated annual TB incidence of 21,000 cases, 8000 of these being infectious. This paper describes a partnership between the TB programme and a Non Governmental Organization (NGO), which began with a methodological analysis of the problems faced by the programme to help identify other key organizations, who might usefully be involved. The work focussed on ‘networking’ to ensure the optimum use of existing resources. The problems encountered affected all levels of TB control from access to drug supply and treatment. The major issues related to an inadequate public health infrastructure resulting in poor technical and administrative support to field staff. There was confusion over roles of the health personnel in the TB programme and the public health facility, as well as poor technical performance. Partnerships were found to be useful in addressing the following areas: (1) the implementation of an external quality assurance scheme for sputum microscopy through involvement of microbiologists from large hospitals and research organizations; (2) training and capacity strengthening of programme and public health facility staff through innovative training and team building exercises organized by the programme, NGOs and the private sector; (3) development of Information, Education and Communication (IEC) material through partnerships with NGOs, and (4) the involvement of local NGOs and private doctors to increase case finding and to improve access to direct observation of treatment (DOT). The paper discusses the lessons learnt in this process and identifies some of the key issues in urban TB control, for consideration by policy makers.

Persistent high incidence of tuberculosis in immigrants in a low-incidence country.

Immigration from areas of high incidence is thought to have fueled the resurgence of tuberculosis (TB) in areas of low incidence. To reduce the risk of disease in low-incidence areas, the main countermeasure has been the screening of immigrants on arrival. This measure is based on the assumption of a prompt decline in the incidence of TB in immigrants during their first few years of residence in a country with low overall incidence. We have documented that this assumption is not true for 619 Somali immigrants reported in Denmark as having TB. The annual incidence of TB declined only gradually during the first 7 years of residence, from an initial 2,000 per 100,000 to 700 per 100,000. The decline was described by an exponential function with a half-time of 5.7 (95% confidence interval 4.0 to 9.7) years. This finding seriously challenges the adequacy of the customary practice of screening solely on arrival.

Spatial patterns of tuberculosis incidence in Cologne (Germany)

In many European countries, the decline of tuberculosis notification rates levelled off in the mid 1980s. Germany has been facing only a very modest resurgence of tuberculosis (TB) in the early 1990s, but until now, the notification rate does not yet fulfil the WHO definition of a low incidence country. Mainly immigration from high incidence countries is held responsible for the delayed decline and temporary increase of TB. This paper seeks to investigate the inner-urban strength of association between tuberculosis and several potential risk factors in the city of Cologne using geographical and statistical methods within a small-area division based, GIS-supported ecological study, which never before has been conducted for a German city. Standardised annual TB incidence rates for 78 urban subdistricts between 1986 and 1997, disaggregated by age, have been analysed. Twelve independent variables representing contemporary ethnic and socio-economic conditions are used to calculate Poisson regression models. For the entire population and for the <60 age group, a strong positive association was found between tuberculosis incidence and share of immigrants. Interestingly enough the share of German-origin immigrants from eastern Europe was seen not to be instrumental in increasing TB rates. Reflecting strong ecological correlations between variables depicting economic conditions and TB as well as immigration variables, the deprivation of certain ethnicities rather than high prevalence immigration background is inferred to be significant to TB level. As for the 60+ age group regression analysis fails to model the TB incidence patterns sufficiently it seems reasonable to assume an autonomous, spatially disaggregated TB epidemic of the elderly, echoing a severe post-war epidemic by reactivation, only marginally associated with contemporary living conditions, but contributing substantially to the current TB incidence level. This assumption is reinforced by further results of the statistical analysis (deviance of regression null models, testing for Normal distribution, time trends). It could be shown that in Cologne the HIV/AIDS epidemic is not significantly influencing the TB incidence rate of men aged 30–49 being the most AIDS-afflicted population subgroup.

Evolución de la incidencia de la tuberculosis en el Área Sur de Sevilla en la década de los noventa

To describe the incidence of tuberculosis (TB) in the hospital area of Seville-South between 1990 and 1999. Study of the incidence of TB in the area's population between 1990 and 1999 by way of periodic survey of informants who were likely to see cases. The annual incidence of TB rose from 1990 (26.64/105) to its peak in 1992 (38.3/105), stabilized between 1992 and 1995, and later fell to 15.7/105 in 1999. Bacillary cases followed a similar pattern, with a peak of 13.76/105 in 1992 and a low of 6.06/105 in 1998. The annual incidence of TB-AIDS rose between 1990 (2.63/105) and 1995 (9.08/105), and then fell to 4.13/105 by 1999. The highest incidences were in the 25-to-34-year-old range in the periods from 1990 to 1993 (50.74/105) and 1994 to 1996 (61.49/105), whereas the incidence decreased among 55-to-64-year-olds (28.55/105) from 1997 to 1999. The age distribution was affected by rates in the TB-AIDS group, which contributed 48%, 50% and 55% in each period, respectively, for individuals in the 25-to-34-year-old range. The annual incidence of TB was 41,1% lower in 1999 than in 1990, as a result of the marked decrease beginning in the middle of the decade. The impact of TB-AIDS patients on the evolution of annual incidence and on age distribution was considerable throughout the decade.

The Epidemic Impact of Therapy for Early Latent Tuberculosis Infection

PURPOSE: Contact investigation programs that identify and offer therapy to persons in the early stage of latent tuberculosis (TB) infection may have a substantial impact on the epidemic, since these programs identify individuals who are at high risk of developing active TB. We quantify the impact that treatment of persons with early latent TB infection has on TB incidence and identify the combination of rates of treatment for active TB and treatment for early latent TB infection which will eliminate a TB epidemic. METHODS: A mathematical model of a TB epidemic is formulated which divides infected persons into 3 subgroups: early latent TB infection (early LTBI), long-term latent TB infection (long-term LTBI), and active TB. Infected persons are initially considered to be in the early LTBI phase, from which they can either progress to long-term LTBI, or to active TB. Persons with long-term LTBI also progress to active TB, but at a lower rate. The basic reproductive rate is derived for the model and used to calculate the combinations of therapy for active TB and early LTBI which will eliminate the epidemic. (The basic reproductive rate is defined as the number of secondary cases caused by one infectious case in a population of susceptible persons. When the basic reproductive rate is less than 1, the epidemic will eventually be eliminated.) Computer simulations of the model are used to demonstrate the impact over time of increasing treatment for early LTBI. RESULTS: The model demonstrates that the addition of a program which treats persons with early LTBI will substantially reduce incidence of active TB, and in some cases, may eliminate the epidemic. For example, if the initial annual incidence of active TB in a population is constant at 110 per 100,000 persons, and the current treatment rate for active TB is 80%, then adding a program which treats 20% of persons with early LTBI will reduce the annual incidence of active TB to 42 per 100,000 persons. Under the same initial conditions, the addition of a control program which treats over 33% of persons with early LTBI will lead to eventual elimination of TB. CONCLUSION: Treatment of early latent TB infection is an effective adjunct to treatment of active TB in controlling TB epidemics. Extending programs such as contact investigation which identify persons with recent infection will substantially impact TB epidemics.

Predicting the Impact of Pre-Exposure and Post-Exposure Tuberculosis Vaccines in India

PURPOSE: Although the Bacille Calmette-Guerin (BCG) vaccine is widely used in many developing countries, it has limited efficacy in preventing tuberculosis (TB). Of the newer TB vaccines which are currently being developed, some are intended to prevent disease in uninfected persons (pre-exposure vaccines) and others are intended to prevent the development of disease in latently infected persons (post-exposure vaccines.) We predict the impact that mass vaccination campaigns with moderate to high efficacy pre-exposure and post-exposure vaccines would have on the TB epidemic in India. We calculate the effect that these vaccines would have on the the incidence of active TB and the death rate from TB in India over twenty years. METHODS: We use mathematical models to make our predictions. Two models of TB epidemics are developed to represent the population effects of pre-exposure and post-exposure vaccines. Each model includes the various ways in which a vaccine may be fail: immunity may be conferred to only some of those vaccinated; immunity may only be partially protective to those who acquire it; immunity may wane over time. Time-dependent uncertainty and sensitivity analysis is performed using latin hypercube sampling, a stratified form of Monte Carlo sampling. This analysis enables us to include uncertainty in multiple parameters and transform this into prediction uncertainty. The sensitivity analysis is carried out over time to determine the vaccine characteristics and population parameters most important in determining the vaccines'impact at different time intervals. RESULTS: The model reveals that in general a post-exposure vaccine will have greater impact than a pre-exposure vaccine on the incidence of active TB and death from TB. For example, if the initial annual incidence of active TB is 187 cases per 100,000 persons then a post-exposure vaccine which is applied to 60-90% of the population and which has 50–80% efficacy and an average waning time of 10–30 years will reduce the annual incidence by a median of 33.6% (2.5th percentile 18.3% - 97.5th 62.8%) over 20 years. In contrast a pre-exposure vaccine applied to a population with the same initial incidence and the same efficacy, coverage rate, and waning rate will reduce the incidence by a median of 16.5% (2.5th percentile 11.6% - 97.5th 24.3%) over 20 years. A post-exposure vaccine will also be more effective in reducing the death rate from TB over 20 years. CONCLUSION: A post-exposure vaccine is likely to make the greatest impact on reducing the rate of active TB and death from TB in India.

Effects of sustained control of brushtail possums on levels of Mycobacterium bovis infection in cattle and brushtail possum populations from Hohotaka, New Zealand

Aims. To examine the effect of reducing the abundance of brushtail possums (Eichosurus vulpecula) on the distribution and prevalence of bovine tuberculosis (Mycobacterium bovis,Tb) in possums and the incidence of Tb in domestic cattle on a group of farms in the central North Island, New Zealand. Methods. The cumulative yearly incidence of Tb infection from 12 cattle herds was estimated from annual tuberculin testing and abattoir inspection data over the period 1983-98. Intensive control of possum populations began for six of the herds in 1988, five herds in 1994 and the remaining herd in 1996. The prevalence and distribution of macroscopic M. bovis infection in possums and an index of possum abundance was estimated during yearly cross-sectional surveys from 1988 to 1998. This enabled formal testing of the link between the abundance of tuberculous possums and the incidence of Tb in cattle. Results. Before possum control, infected possums were clustered in foci on or adjacent to the farms with the highest annual incidence of tuberculosis in cattle, and had an overall prevalence of macroscopic M. bovis infection of 2.3%. The prevalence of disease declined to zero with ongoing possum control, although infected possums continued to be found during the first 5 years of control. Maintaining the possum population at an average of 22.1% of its pre-control density significantly reduced the odds of the cumulative yearly incidence of Tb in cattle by 77% during the first 5 years of possum control and a further 65% in the second 5year period. Nine of 11 tuberculous possums identified since the start of possum control were found within the areas where infected possums were clustered during the pre-control survey, suggesting that the persistence of infection within these clusters rather than infected immigrants was the source of ongoing disease. Annual estimates of the prevalence of tuberculous possums broadly followed the predictions of Barlow's possum-Tb model for a controlled possum population. Conclusion. The results support the hypothesis that tuberculous possums transmit bovine tuberculosis to domestic cattle, and therefore that reducing the abundance of tuberculous possums reduces the incidence of Tb in cattle. If the level of possum culling is sufficient, it appears that M. bovis infection may be eradicated from possum populations. Better information on population density, rate of increase and annual culling rates would have been needed for a truly independent examination of the Barlow possum-Tb model.

Differences in tuberculosis incidence rates in township and in rural populations in Ntcheu district, Malawi

There has been a large upsurge of tuberculosis (TB) in many countries in sub-Saharan Africa, mainly as a result of the co-existing human immunodeficiency virus (HIV) epidemic. Malawi has had a well-run National TB Control Programme (NTP) with good registration and recording of cases. For some years the NTP has had the impression that TB in the country is concentrated around townships and is less prevalent in the rural areas. This impression was investigated in a rural district (Ntcheu District) in Malawi. Data on new TB cases were collected from the district TB register for the years 1992–1996 and average annual TB incidence rates per 100 000 for semi-urban and rural populations were calculated for this period. There was a significantly higher incidence of TB, particularly amongst cases with smear-negative pulmonary TB and extrapulmonary TB, in the semi-urban population compared with the rural population. Possible explanations could be higher HIV seroprevalence rates in semi-urban areas compared with rural areas, under-diagnosis at health centres or poor access to medical facilities for rural people.

The epidemiology of tuberculosis in gold miners with silicosis.

The elevated risk of tuberculosis in subjects with silicosis is widely accepted but has not been quantified in a population with a high prevalence of tuberculosis. In this study, a cohort of 1,153 older gold miners with and without silicosis who had not had tuberculosis have been followed for 7 yr by a routine mine surveillance program for detection of tuberculosis. One hundred seventy-eight of the men developed tuberculosis. The annual incidence of tuberculosis was 981/100,000 in the 335 men without silicosis and 2,707/100,000 in the 818 men with silicosis. The relative risk for tuberculosis was 2.8 (95% CI, 1.9 to 4.1) for men with silicosis compared with that in the men without silicosis. The incidence of tuberculosis increased from 1% per annum (pa) for the men without silicosis to 2.2% pa for the men with silicosis with Category 1 nodule profusion, 2.9% pa for those with Category 2, and 6.3% pa for those with Category 3 silicosis. This study has confirmed and quantified the high risk of pulmonary and of extrapulmonary tuberculosis in men with silicosis. The incidence of tuberculosis during this 7-yr study suggests that one quarter of these men with silicosis will have developed tuberculosis by 60 yr of age.