Cattle-to-cattle transmission of Mycobacterium bovis.

This review, illustrated with data on the characteristics of herds infected with Mycobacterium bovis (TB) in Great Britain (GB), attempts to identify the role of cattle-to-cattle transmission (CCT) of TB. CCT plays a part in the entry of infection into herds, through purchased infected animals or contiguous spread, although CCT can have a relatively small role in comparison with an established wildlife source. Experimental studies have shown that it is possible for CCT to occur within herds. In 1999, more than one reactor was found in over two-thirds of confirmed TB incidents in Great Britain. The details of transmission from an infectious animal to a susceptible animal are described: proximate, which depends on factors such as closeness of contact and ventilation, or indirect, which also depends on survival outside the host. Herd size is a risk factor for the incidence of TB, both in herds and in individual cattle. Control of TB is considered in relation to the skin test: failure of the test to remove all infected animals from incidents is possible, but probably of less significance than failure to prevent reinfection from sources external to the herd. It is concluded that CCT may have significance in determining the total number of reactors. Safeguarding herds from other sources of TB is likely to reduce CCT as a side effect.     

Mycobacterium bovis in rural Tanzania: risk factors for infection in human and cattle populations

Although bovine tuberculosis is widespread throughout Africa, very little is known about risk factors for Mycobacterium bovis infection in either human or cattle populations. A human case-control study was conducted in northern Tanzania, comparing risk factors and prevalence of cattle interdermal test positives of cases (cervical adenitis cases from which M. bovis was isolated) with age- and sex-matched controls (selected at random from potential hospital attendees within the community). A cattle cross-sectional study was also set-up involving 27 villages selected at random in four districts, with 10,549 cattle and 622 herds tested, and questionnaire surveys conducted in 239 households. M. bovis was confirmed in seven of 65 (10.8%) human cervical adenitis cases, of which only one came from a household owning infected cattle. M. bovis in human patients was associated with families in which a confirmed diagnosis of tuberculosis had previously been made (p<0.001) and with households far (>100m) from neighbours (p=0.003). In cattle, overall prevalence of intradermal test positives was low at 0.9% (0.70-1.06%), but widespread, with 11.8% (8.44-13.17%) herds containing at least one reactor. Prevalence of intradermal test positives increased significantly with cattle age (p<0.001). Herds with the following risk factors had a significantly greater prevalence of intradermal test positives: >50 cattle in the herd (p=0.024); herds housed inside at night (p=0.021) and herds in contact with wildlife (p=0.041). Furthermore, villages that experienced annual flooding had a higher prevalence of infection (p=0.043).     

HIV testing practices of TB patients after introduction of a new testing policy in Kiev City, Ukraine.

SETTING: The Kiev City Health Administration published a new policy for human immunodeficiency virus (HIV) testing of tuberculosis (TB) patients. According to this policy, all TB patients should be offered voluntary HIV testing after counselling. OBJECTIVE: To evaluate the implementation of the new HIV testing policy and to determine the HIV prevalence in TB patients in Kiev City. DESIGN: TB patient medical records were retrieved from eight TB facilities in Kiev City. They were reviewed for information about offering an HIV test, accepting to be HIV tested and outcome of the HIV test. Information was collected about patient characteristics and TB risk groups. RESULTS: Of 914 patients, 75% were offered HIV testing. Females were less frequently and alcohol abusers more frequently offered HIV testing. Of the patients who were offered HIV testing, 84% accepted. Of the 574 who were HIV tested, 36 (6.3%) had a positive test result. CONCLUSION: Not all TB facilities adhere strictly to the new policy. HIV testing seemed to be targeted to individuals with a high risk for HIV infection. To improve adherence to the new policy we recommend training of TB physicians in voluntary counselling and testing. The HIV prevalence among TB patients in Kiev City was 6.3%.     

Tuberculosis infection in drug users: interferon-gamma release assay performance.

SETTING: An inner city neighborhood in Houston, Texas, known for a high rate of drug use. OBJECTIVE: To determine the prevalence of latent tuberculosis infection (LTBI) using the QuantiFERON-TB Gold (QFT-G) test, the TSPOT.TB test and the tuberculin skin test (TST) in drug users and to evaluate the performance of the QFT-G and TSPOT.TB tests vs. the TST. DESIGN: Cross-sectional study. Bivariate and multivariate logistic regression analyses were used to determine risks associated with each test outcome. RESULTS: The prevalence of LTBI in 119 drug users studied was 28% by TST and 34% by QFT-G and T-SPOT.TB. Kappa statistics indicated fair to moderate concordance between QFT-G and TSPOT.TB vs. TST. About one-fifth of the population that tested negative with TST was positive with either QFT-G or T-SPOT.TB. On multivariate analysis, the likelihood of testing QFT-positive or T-SPOT.TB-positive increased by 8% and 6%, respectively, for every year of age; TST positivity was associated with smoking crack at home; being Caucasian or having a history of alcohol use was positively associated with a positive T-SPOT.TB test. CONCLUSION: Interferon-gamma release assays (IGRAs) are superior to the TST in drug users with a higher prevalence of LTBI. Future studies need to assess the predictive value of IGRAs on the progression from LTBI to active TB in high-risk populations.     

Prevalence and risk factors for latent tuberculosis infection among health care workers in Georgia.

BACKGROUND: Tuberculosis (TB) is a major public health problem in Georgia, but few TB infection control measures have been implemented in health care facilities. OBJECTIVE: To assess the prevalence and risk factors for latent TB infection (LTBI) among Georgian health care workers (HCWs) using two diagnostic tests, the tuberculin skin test (TST) and the QuantiFERON-TB Gold In Tube test (QFT-3G), an interferon-gamma release assay. METHODS: A cross-sectional study was conducted between June and August 2006 among HCWs at the Georgian National TB Program. RESULTS: Of 265 HCWs enrolled, 177 (67%) had a positive TST and 159 (60%) had a positive QFT-3G; 203 (77%) had a positive result for at least one of the tests and 50% tested positive for both tests. There was moderately good agreement between the tests (74%, kappa = 0.43, 95%CI 0.33-0.55). In multivariate analysis, employment for >5 years was associated with increased risk of a positive TST (OR 5.09, 95%CI 2.77-9.33) and QFT-3G (OR 2.26, 95%CI 1.27-4.01); age >30 years was associated with an increased risk of a positive QFT-3G (OR 2.91, 95%CI 1.32-6.43). DISCUSSION: A high prevalence of LTBI was found among Georgian HCWs and longer duration of employment was associated with increased risk. These data highlight the need for effective TB infection control measures and provide important baseline information as TB infection control measures are implemented.     

Mycobacterium caprae in cattle and humans in Croatia.

SETTING: This paper describes an outbreak of human and related bovine tuberculosis (TB) caused by Mycobacterium caprae in Croatia. A 13-year-old boy clinically presented enlargement of cervical lymph node with consecutive isolation of M. caprae. His 7-year-old sister, who had no clinical signs of disease, hyper-reacted to the purified protein derivative (PPD) test (>25 mm) and peribronchial infiltration was found by radiology. The children came from a family that ran a small-sized cattle dairy farm. DESIGN: All cattle on the farm were subjected to cutaneous TB testing: six of the 14 reacted positive, while three were suspicious. The entire herd was slaughtered, their carcasses examined and collected material subjected to pertinent diagnostic procedures. RESULTS: Gross examination findings consistent with TB were observed in the PPD-positive cows. Mycobacteria isolated from the boy and cattle were identified by classical and molecular methods, confirming M. caprae as the causative agent. CONCLUSION: Although not bacteriologically proven, consumption of raw milk or non-pasteurised milk products from infected dairy cattle was suspected as the source of infection in humans. Our findings confirm the domination of M. caprae among cattle in Croatia and represent the first evidence of M. caprae infection in humans in Croatia.     

The relationship between the parasitological prevalence of trypanosomal infections in cattle and herd average packed cell volume

The relationship between prevalence of trypanosomal infections (Trypanosoma congolense) and average packed cell volume (PCV) in herds of communally managed adult Angoni breed cattle was investigated in four districts of eastern Zambia. In all areas, regression analyses showed that the herd average PCV decreased with increasing prevalence of trypanosomal infections. The slope of the equation between average PCV and trypanosome prevalence decreased with increasing prevalence of trypanosomal infections. For the same increase in prevalence of trypanosomal infection, the decrease in herd PCV was higher in the areas with low to medium prevalence. Season of sampling also determined the slope of the regression equation. For the same increase in prevalence of trypanosomal infection, the decrease in herd PCV was higher during the dry compared to the rainy season suggesting that trypanosomosis is less well tolerated during the dry season. Results from the study suggest that the relationship between the prevalence of trypanosomal infections and herd average PCV could be a useful tool in the management of trypanosomosis and planning of its control. Reasons for the spatial and temporal variations in the relationship are discussed.     

Detection of relapsing fever spirochetes (Borrelia hermsii and Borrelia coriaceae) in free-ranging mule deer (Odocoileus hemionus) from Nevada, United States

Surveillance of mule deer (Odocoileus hemionus, Rafinesque, 1917) populations for tick-borne diseases has helped define the distribution of these pathogens and their subsequent risk of transmission to humans and domestic animals. We surveyed three mule deer herds across the state of Nevada for infection with relapsing fever Borrelia spp. spirochetes. Bacterial prevalence varied by the county where deer were sampled but Borrelia spirochetes were detected in 7.7% of all deer sampled. Infected deer were identified in every location from which mule deer samples were obtained. Sequencing of the Borrelia intergenic spacer gene (IGS) revealed that one individual was infected with Borrelia coriaceae and all others were infected with Borrelia hermsii. The vector of B. hermsii, Ornithodoros hermsi (Acari: Argasidae, Wheeler, Herms, and Meyer, 1935), feeds primarily on wild rodents and has not been identified infesting deer. Additionally, Ornithodoros coriaceus (Acari: Argasidae, Koch, 1844), which readily feeds on deer and is frequently infected with B. coriaceae, has not been shown to be a competent vector for B. hermsii. Our data represent the first sylvatic evidence of B. hermsii infection in mule deer. Additionally, our data provide evidence that infection with relapsing fever spirochetes in Nevada is wide ranging in the state's deer populations.     

Use of a T-cell-based test for detection of tuberculosis infection among immunocompromised patients.

The aim of this study was to compare the performance of the T-SPOT.TB test, a T-cell-based test, with the tuberculin skin test (TST) in the diagnosis of latent tuberculosis (TB) infection. The study was carried out in 138 immunosuppressed haematology patients who had been nosocomially exposed to a case of smear-positive TB. Overall, 44.2% of the contacts were positive by T-SPOT.TB test, and 17.4% by TST (concordance 67.8%). The apparent prevalence of infection fell from 25.9 to 14.5% with the TST with increasing immunosuppression, although this difference was not significant. In contrast, the apparent prevalence of infection with the T-SPOT.TB test was unaffected at 44.6 and 44.3%, respectively. The T-SPOT.TB test had an overall indeterminate rate of 4.3%, and this was also unaffected by the level of immunosuppression. This study suggests that the T-SPOT.TB test maintains its sensitivity and performance in immunocompromised patients, identifying a large number of truly infected patients anergic to the tuberculin skin test.     

BCG coverage and the annual risk of tuberculosis infection over a 14-year period in the Philippines assessed from the Nationwide Prevalence Surveys.

SETTING: A prevalence survey of tuberculosis (TB) infection was undertaken in the Philippines, a developing country in the Western Pacific region. OBJECTIVE: To determine the bacille Calmette Guerin (BCG) vaccination rate, the prevalence of TB infection and the annual risk of TB infection (ARTI). METHODS: A nationwide stratified multi-stage cluster survey of 21,960 individuals. BCG scar verification and tuberculin test were performed on those aged > or =2 months. The ARTI was calculated using the prevalence rates of TB infection in children aged 5-9 years. RESULTS: BCG scars were noted in 66% of the study population. The prevalence of TB infection was 63.4% among unvaccinated individuals. The prevalence rate was higher in males in both urban and rural areas. With both sexes combined, urban and rural communities had similar prevalence rates. In children aged 5-9 years, the prevalence rate was 16.1% (males 17.4%, females 14.9%), corresponding to an ARTI of 2.3% (males 2.5%, females 2.1%). CONCLUSION: BCG coverage increased substantially between 1981-1983 and 1997. The ARTI, however, was virtually unchanged, indicating that morbidity due to TB continued to be high.     

Preliminary observations on Mycobacterium spp. in dairy cattle in Ecuador

This study evaluated bovine tuberculosis in Mejia canton, a major dairy cattle production region in Ecuador. Randomly selected cattle (1,012 from 59 farms) classified according to herd size were tested by the single tuberculin test (STT). Sixty days later, positive reactors were tested again by the comparative tuberculin test (CTT). In addition, tissue samples from two STT-CTT-positive reactors detected on a farm were obtained in a local slaughterhouse and analyzed bacteriologically. A total of 4.24% of the cattle were positive in the STT and 3.85% were positive in the CTT, with the highest number (7.95%) in large herds versus 3.4% in medium herds and 0.3% in small herds. Mycobacterium bovis was isolated from mesenteric lymph nodes and lungs of one animal. A 16S ribosomal RNA-based polymerase chain reaction confirmed culture results and differentiated mycobacteria other than M. tuberculosis. This study confirms the zoonotic importance of tuberculosis in Ecuadorian dairy cattle with herd size likely to be a crucial parameter in the prevalence of the disease. The implementation of a national control program is necessary and should be based on the detection of positive cattle by STT in combination with CTT.     

Tuberculin survey among school-aged children in Ahvaz, Iran, 2006.

BACKGROUND AND OBJECTIVE: The tuberculin test is widely used for the diagnosis of tuberculosis (TB) in children, as it is the only one to provide evidence of infection with Mycobacterium tuberculosis. Our objective was to estimate the prevalence of TB infection, the annual risk of infection (ARI), and the incidence of active TB in school children. METHODS: A cross-sectional study was carried out in Ahvaz, a city of southern Iran, in 2006. A questionnaire was used to collect information, including demographic characteristics, bacillus Calmette-Guérin (BCG) vaccination history, and household contact with active TB. Tuberculin testing was performed. Reactivity that measured < 5 mm was considered negative, between 5 and 9 mm was considered doubtful, and > or = 10mm was considered positive. Chest radiographs were obtained as part of the evaluation for children with a positive result. RESULTS: A total of 3906 children with a mean+/-standard deviation (SD) age of 10.59+/-2.63 years (51% female, 49% male) were entered into our study. Of these, 3338 children (85.5%) did not develop a reaction (0mm), 243 (6.2%) had reactivity of 1-4mm, 238 (6.1%) had reactivity of 5-9 mm, and 87 (2.2%) had reactivity of > or = 10 mm. More than 90% of the children had received the BCG vaccine in the first week of life. The ARI rate was 0.5% and the estimated case of smear-positive TB was approximately 25 per 100000 population. Only three children were diagnosed with active TB, a prevalence of 75 per 100000 population. CONCLUSIONS: Tuberculin testing using 5TU-PPD (5 tuberculin units of purified protein derivative) is a valuable diagnostic test for latent TB and active TB in childhood. BCG vaccination has no remarkable effect on the interpretation of tuberculin reactivity. The incidence rate of active pulmonary TB in children in the region of study is of concern.     

Outbreak of tuberculosis in a homeless population involving multiple sites of transmission.

SETTING: During 2002-2003, a large outbreak of tuberculosis (TB) occurred among persons using multiple homeless facilities in King County, Washington. OBJECTIVE: To control the transmission of TB in multiple settings. DESIGN: In 2002, contacts exposed to patients in homeless facilities were screened using tuberculin skin tests (TSTs) and symptom review. Based on these screening results, sites of transmission were identified and prioritised, and exposed cohorts at these sites were offered intensive screening tests in 2003 (e.g., symptom review, TST, chest radiograph [CXR], sputum examination and culture). Mycobacterium tuberculosis isolates from patients were genotyped using PCR-based methods to identify outbreak-associated patients quickly. RESULTS: During 2002-2003, 48 (15%) of 313 patients diagnosed in King County were outbreak-associated; 47 culture-positive patients had isolates that matched the outbreak strain by genotyping. Three facilities visited by >12 patients in 2002 had a higher prevalence of TST positive results (approximately 30%) among clients compared with the background rate (7%) in the homeless community. Screening contacts with one sputum culture was as sensitive as CXR in detecting TB disease (77% vs. 62%, respectively). CONCLUSIONS: A comprehensive, resource-intensive approach likely helped to control transmission. This outbreak highlights the vulnerability of homeless populations and the need to maintain robust TB programs in urban settings.     

Screening for acute HIV infection in South Africa: finding acute and chronic disease*

Background

The yield of screening for acute HIV infection among general medical patients in resource‐scarce settings remains unclear. Our objective was to evaluate the strategy of using pooled HIV plasma RNA to diagnose acute HIV infection in patients with negative or discordant rapid HIV antibody tests in Durban, South Africa.

Methods

We prospectively enrolled patients with negative or discordant rapid HIV antibody tests from a routine HIV screening programme in an out‐patient department in Durban with an HIV prevalence of 48%. Study participants underwent venipuncture for pooled qualitative HIV RNA, and, if this was positive, quantitative RNA, enzyme immunoassay and Western blot (WB). Patients with negative or indeterminate WB and positive quantitative HIV RNA were considered acutely infected. Those with chronic infection (positive RNA and WB) despite negative or discordant rapid HIV tests were considered to have had false negative rapid antibody tests.

Results

Nine hundred and ninety‐four participants were enrolled with either negative (n=976) or discordant (n=18) rapid test results. Eleven [1.1%; 95% confidence interval (CI) 0.6–2.0%] had acute HIV infection, and an additional 20 (2.0%; 95% CI 1.3–3.1%) had chronic HIV infection (false negative rapid test).

Conclusions

One per cent of out‐patients with negative or discordant rapid HIV tests in Durban, South Africa had acute HIV infection readily detectable through pooled serum HIV RNA screening. Pooled RNA testing also identified an additional 2% of patients with chronic HIV infection. HIV RNA screening has the potential to identify both acute and chronic HIV infections that are otherwise missed by standard HIV testing algorithms.     

Risk of tuberculosis infection and disease associated with work in health care settings.

BACKGROUND: Tuberculosis (TB) in health care workers (HCWs) was not considered a serious problem following the advent of effective antibiotic therapy. Interest was re-stimulated by the occurrence of several major nosocomial outbreaks. METHODS: We have reviewed the available published literature regarding prevalence and incidence of TB infection and disease among HCWs in countries categorised by mean income. We included studies published in English since 1960 from low- and middle-income countries (LMICs) and since 1990 from high-income countries (HICs). We excluded outbreak reports and studies based only on questionnaires. RESULTS: The median prevalence of latent TB infection (LTBI) in HCWs was 63% (range 33-79%) in LMICs and 24% in HICs (4-46%). Among HCWs from LMICs, LTBI was consistently associated with markers of occupational exposure, but in HICs it was more often associated with non-occupational factors. The median annual incidence of TB infection attributable to health care work was 5.8% (range 0-11%) in LMICs and 1.1% (0.2-12%) in HICs. Rates of active TB in HCWs were consistently higher than in the general population in all countries, although findings were variable in HICs. Administrative infection control measures had a modest impact in LMICs, yet seemed the most effective in HICs. CONCLUSIONS: TB remains a very important occupational risk for HCWs in LMICs and for workers in some institutions in HICs. Risk appears particularly high when there is increased exposure combined with inadequate infection control measures.     

Airway hyperresponsiveness by methacholine challenge testing following negative exercise challenge.

BACKGROUND: Exercise challenge testing (ECT) to diagnose exercise-induced bronchospasm has been demonstrated to be an insensitive screening test to demonstrate the presence or absence of airway hyperreactivity. Previous studies have not compared this procedure to methacholine challenge testing (MCT) in a clinical setting. OBJECTIVE: To determine the frequency of positive MCT in subjects with exertional dyspnea, normal baseline spirometry, and negative ECT. METHODS: Observational study of 215 military patients at an Army Community Hospital referred for evaluation of exertional dyspnea with normal baseline spirometry. Subjects were further evaluated with ECT on a graded treadmill with pre- and postexercise spirometry. Those without evidence of bronchial hyperreactivity as defined by a 15% decrease in FEV1 postexercise were evaluated with methacholine challenge testing (MCT). RESULTS: Two hundred ten military subjects were evaluated. Eighty-two patients underwent ECT as the only method of bronchoprovocation testing with 25 positive tests (57 were negative but not referred for further testing). The remaining 128 patients with a negative ECT underwent MCT. Seventy-six (59%) had a negative MCT and 52 (41%) had a positive MCT. Of the positive MCT studies, 74% were positive at a methacholine concentration of 2.5 mg/mL or less. CONCLUSIONS: Our study demonstrates that a significant number of patients being evaluated for exertional dyspnea will have a positive MCT after a negative ECT. Our findings lead us to question the utility of ECT as an initial diagnostic test for the exercise-induced bronchospasm.     

Tuberculosis in patients with human immunodeficiency virus infection

Tuberculosis (TB) is the major opportunistic infection of human immunodeficiency virus (HIV)-infected persons worldwide. Human immunodeficiency virus infection is the most potent known risk factor for reactivation of latent Mycobacterium tuberculosis infection, and TB disease appears to increase the rate of HIV progression. Pulmonary disease is seen in most patients, including a large proportion of those with extrapulmonary disease. Failure to suspect TB and to order the appropriate diagnostic tests is the most common reason for diagnostic delays. With advancing HIV infection, tuberculin skin test reactivity decreases along with reactivity to nonspecific antigens such as mumps, tetanus toxoid, and Candida; anergy testing need not be a routine component of tuberculosis screening of HIV-infected persons. The diagnosis depends on identifying the organism on smears or cultures; direct amplification tests may facilitate rapid identification of M. tuberculosis, but the relatively low sensitivity in smear-negative specimens limits their use. Also, these tests must be used in conjunction with the clinical assessment, and they must always be performed in conjunction with microscopy and standard culture. Shorter courses of combination preventive therapy of patients with latent tuberculous infection are effective, but the potential advantages of improved adherence and reduced costs of shorter courses should be balanced with an increased risk secondary to ongoing TB exposure in areas with a high TB prevalence. Six months of treatment for active tuberculosis is recommended, unless the response of a particular patient is slow or otherwise suboptimal. The use of highly active antiretroviral therapy (HAART) made a remarkable impact on the course or HIV disease, but raises several issues with respect to HIV-related TB. Drug interactions necessitate either a non-rifamycin-based regimen or a rifabutin-based regimen in patients on HAART treated for TB.     

The cost-effectiveness of diagnostic testing strategies for Helicobacter pylori

OBJECTIVE: Several noninvasive methods are now available for diagnosing Helicobacter pylori infection. Because the prevalence of H. pylori infection is variable in patients requiring testing, the optimal testing strategies may vary under different conditions. The aim of this study was to evaluate the cost-effectiveness of competing diagnostic strategies for H. pylori in patients with varying H. pylori prevalence. METHODS: A decision analysis was performed comparing the costs per number of correct diagnoses achieved by alternative sequential testing strategies. Estimates of H. pylori prevalence and test characteristics were derived from a systematic review of the MEDLINE bibliographic database. Cost estimates were derived from the 2000 Medicare Fee Schedule. RESULTS: The enzyme-linked immunosorbent assay (ELISA) test had the lowest cost per correct diagnosis at low (30%), intermediate (60%), and high (90%) prevalence ($90-$95/correct diagnosis), but its diagnostic accuracy was low (80-84%). At low and intermediate prevalence the stool test was more accurate (93%), with an average cost of $126-$127 per correct diagnosis. Additional confirmatory testing of positive or negative tests increased the diagnostic accuracy of the stool test, but had high incremental costs. ELISA testing was preferable when prevalence rates were very high (90%), and using a confirmatory urea breath test for negative ELISA tests increased the diagnostic accuracy to 96%, with modest incremental costs. If the cost of the breath test was <$50 or if the cost of the stool test is >$82, breath testing became preferable to stool testing. If the cost of the stool test fell to <$20, it became preferable to ELISA. Similarly, if the cost of the ELISA serology was >$39 then stool testing became preferable at all prevalence rates. Fingerstick whole blood tests were not cost-effective. CONCLUSIONS: The choice of an initial test for H. pylori detection depends on the prevalence of H. pylori infection and the value placed on increased diagnostic accuracy. Although ELISA results in the lowest cost-effectiveness ratios, in patients at low-intermediate pretest probability of infection, the stool test provides increased accuracy, with modest incremental costs.     

Tuberculosis in homeless, residential care facilities, prisons, nursing homes, and other close communities

Tuberculosis (TB) is a problem in some institutions, but not in others. Six factors may be used to assess the risk of TB in an institution: the entrance-point prevalence of infection among institutional residents and staff, the potential for reactivation, the role of transmission within the institution, the potential for detection of infection and disease, the potential for prevention and treatment of disease, and the potential of the building environment to favor transmission. The aging of the population, the crowding of prisons and the high prevalence of human immunodeficiency virus (HIV) infection are factors currently increasing the likelihood of TB in nursing homes, prisons, drug detoxification centers, and acute hospitals. Entrance-point skin testing, contact testing, periodic retesting, supervised preventive therapy, effective treatment of disease, and the selective application of ultraviolet air disinfection for certain high-risk areas are the suggested control strategies for hospitals, nursing homes, prisons, and chronic care facilities. However, for inner-city shelters and jails skin testing and preventive treatment are usually not possible, and the control strategy shifts to disease detection, isolation, effective long-term treatment, reduced crowding, ultraviolet air disinfection, and periodic testing and treatment of staff.