Spread of Mycobacterium tuberculosis in a community implementing recommended elements of tuberculosis control

Comorbidity and drug resistance of smear-positive pulmonary tuberculosis patients in the yi autonomous prefecture of China: a cross-sectional study

BACKGROUND

Tuberculosis (TB) has a high morbidity and mortality rate, and its prevention and treatment focus is on impoverished areas. The Liangshan Yi Autonomous Prefecture is a typical impoverished area in western China with insufficient medical resources and high HIV positivity. However, there have been few reports of TB and drug resistance in this area.

METHODS

We collected the demographic and clinical data of inpatients with sputum smear positive TB between 2015 and 2021 in an infectious disease hospital in the Liangshan Yi Autonomous Prefecture. Descriptive analyses were used for the epidemiological data. The chi-square test was used to compare categorical variables between the drug-resistant and drug-susceptible groups, and binary logistic regression was used to analyse meaningful variables.

RESULTS

We included 2263 patients, 79.9% of whom were Yi patients. The proportions of HIV (14.4%) and smoking (37.3%) were higher than previously reported. The incidence of extrapulmonary TB (28.5%) was high, and the infection site was different from that reported previously. When drug resistance gene detection was introduced, the proportion of drug-resistant patients became 10.9%. Patients aged 15-44 years (OR 1.817; 95% CI 1.162-2.840; P < 0.01) and 45-59 years (OR 2.175; 95% CI 1.335-3.543; P < 0.01) had significantly higher incidences of drug resistance than children and the elderly. Patients with a cough of ≥ 2 weeks had a significantly higher chance of drug resistance than those with < 2 weeks or no cough symptoms (OR 2.069; 95% CI 1.234-3.469; P < 0.01). Alcoholism (OR 1.741; 95% CI 1.107-2.736; P < 0.05) and high bacterial counts on sputum acid-fast smears (OR 1.846; 95% CI 1.115-3.058; P < 0.05) were significant in the univariate analysis.

CONCLUSIONS

Sputum smear-positive TB predominated in Yi men (15-44 years) with high smoking, alcoholism, and HIV rates. Extrapulmonary TB, especially abdominal TB, prevailed. Recent drug resistance testing revealed higher rates in 15-59 age group and ≥ 2 weeks cough duration. Alcohol abuse and high sputum AFB counts correlated with drug resistance. Strengthen screening and supervision to curb TB transmission and drug-resistant cases in the region.

Pathways of TB Transmission in Children-A Systematic Review of Molecular Epidemiological Studies

The widespread paradigm that younger children usually do not transmit M. tuberculosis complex (Mtbc) to their contacts has not yet been proven by genotypically confirmed transmissions. Therefore, we undertook a systematic review of molecular-epidemiological studies to investigate documented source and secondary TB (tuberculosis) cases among children. We searched the literature published before August 2022 using PubMed, Cochrane, and Google Scholar databases. PRISMA statement was used for systematic review. Of 312 records retrieved, 39 studies including children aged below 15 years offered epidemiological links between cluster members. In the 39 studies from 16 countries, 225 children were reported as cluster members of whom the overwhelming majority were infected by adults. Only 3 children-of those were 2 children aged below 10-were reported to be the definite source cases of 11 other children and 1 adult with genotypically matched Mtbc isolates. To date, molecular-epidemiological studies involving children with verified transmission links are scarce. As far as the heterogeneity of the studies we identified allows, we could conclude that the results confirm the paradigm that children aged below 10 hardly ever transmit Mtbc to others. The true extent of TB transmission through children may, however, be underestimated by those selected studies.

Alarming Tuberculosis Rate Among People Who Inject Drugs in Vietnam

BACKGROUND

The tuberculosis (TB) epidemic is not homogeneous in the general population but presents high-risk groups. People who inject drugs (PWID) are such a group. However, TB among PWID remains largely undocumented. Our goal was to assess the prevalence of TB and the risk factors associated with TB among PWID in Vietnam.

METHODS

We implemented a cross-sectional survey among 2 community-based cohorts of human immunodeficiency virus (HIV)-positive and HIV-negative PWID in Hai Phong. Participants were screened for TB using questions on TB symptoms. Those who reported any symptom were accompanied by peers to the TB clinic for chest x-ray. If the latter was abnormal, a sputum was collected to perform an Xpert MTB/RIF test.

RESULTS

A total of 885 PWID were screened for TB. For both cohorts, most PWID were male (>90.0%), with a median age of 42 years. Beside heroin injection, 52.5% of participants reported smoking methamphetamine, and 63.2% were on methadone. Among HIV-positive PWID (N = 451), 90.4% were on antiretroviral therapy and 81.6% had a viral load <1000 copies/mL. Using a complete-case analysis, the estimated TB prevalence was 2.3% (95% confidence interval [CI], 1.0-4.5) and 2.1% (95% CI, 0.8-4.2) among HIV-positive and HIV-negative people, respectively. Living as a couple, arrest over the past 6 months, homelessness, and smoking methamphetamine were independently associated with TB but not HIV infection.

CONCLUSIONS

In the context of very large antiretroviral therapy coverage, this extremely high rate of TB among PWID requires urgent actions.

The association between proton pump inhibitor use and the risk of tuberculosis: A case-control study

PURPOSE

Few studies have reported an association between proton pump inhibitor (PPI) use and tuberculosis. Tuberculosis incidence is relatively high in Asian people, and an increase in PPI prescriptions has been reported in South Korea. Thus, we investigated the association between PPI use and tuberculosis development.

METHODS

We conducted a case-control study on 25 672 newly diagnosed tuberculosis patients using the National Health Insurance Service-National Sample Cohort (NHIS-NSC) database (2002-2013). We selected a control group without tuberculosis using 1:1 exact matching based on age, sex, index year, insurance type, and income level. We investigated PPI exposure 2 years prior to the index date and classified the subjects into nonuser, continuous user, recent user, and former user groups. Odds ratios (ORs) and 95% confidence intervals (CIs) for tuberculosis development were calculated using conditional logistic regression.

RESULTS

A total of 51 344 cases and controls were analyzed. Recent PPI use (adjusted odds ratio [aOR], 1.28; 95% CI, 1.18-1.39) and continuous PPI use (aOR, 1.13; 95% CI 1.10-1.28) were significantly associated with tuberculosis development, compared with nonuse of PPIs. An increased tuberculosis incidence was not observed in the former use group compared with the nonuse group (aOR 1.05, 95% CI 0.95-1.17).

CONCLUSIONS

In this case-control study, we found that recent PPI use and continuous PPI use were associated with increased tuberculosis development. Although further investigation is needed, the tuberculosis risk accompanying PPI treatment should be considered.

Risk factors for transmission of tuberculosis among United States-born African Americans and Whites

SETTING

Tuberculosis (TB) patients and their contacts enrolled in nine states and the District of Columbia from 16 December 2009 to 31 March 2011.

OBJECTIVE

To evaluate characteristics of TB patients that are predictive of tuberculous infection in their close contacts.

DESIGN

The study population was enrolled from a list of eligible African-American and White TB patients from the TB registry at each site. Information about close contacts was abstracted from the standard reports of each site.

RESULTS

Close contacts of African-American TB patients had twice the risk of infection of contacts of White patients (adjusted risk ratio [aRR] 2.1, 95%CI 1.3-3.4). Close contacts of patients whose sputum was positive for acid-fast bacilli on sputum smear microscopy had 1.6 times the risk of tuberculous infection compared to contacts of smear-negative patients (95%CI 1.1-2.3). TB patients with longer (>3 months) estimated times to diagnosis did not have higher proportions of infected contacts (aRR 1.2, 95%CI 0.9-1.6).

CONCLUSION

African-American race and sputum smear positivity were predictive of tuberculous infection in close contacts. This study did not support previous findings that longer estimated time to diagnosis predicted tuberculous infection in contacts.

Tuberculosis Knowledge, Awareness, and Stigma Among African-Americans in Three Southeastern Counties in the USA: a Qualitative Study of Community Perspectives

To inform strategies to address the tuberculosis (TB) excess among US-born African-Americans, we sought to understand the TB experience in the most highly affected southeastern communities. We conducted semi-structured interviews and focus groups in three communities with a TB excess-urban (Georgia and Tennessee) and rural (North Carolina). Participants from five groups provided diverse perspectives-African-Americans: patients with TB disease or latent TB infection (LTBI), or at high risk of contracting TB; and local community leaders and TB program staff. Few differences emerged between sites. Many participants demonstrated low levels of knowledge and awareness and held many misconceptions about TB. Patients expressed a preference for verbal communication of medical information. Patients reported fear of stigmatization and shunning, but few experienced discrimination. Patient trust for TB program staff was high, though community leaders often assumed the opposite. The findings will help guide interventions to improve knowledge and awareness regarding TB, including specific attention to the role of public and private health care providers in dispelling persistent misinformation about TB. The insight from these communities will help build the scientific foundation required to effectively eliminate health inequities.

Tuberculosis-related stigma leading to an incomplete contact investigation in a low-incidence country

A contact investigation following a case of infectious tuberculosis (TB) reported in a call centre in Milan (Italy) led to the identification of three additional cases that had occurred in employees of the same workplace during the previous 5 years, one of whom was the probable source case. Thirty-three latent infections were also identified. At the time of diagnosis, the source case, because of fear of stigma related to TB, claimed to be unemployed and a contact investigation was not performed in the workplace. Cases were linked through genotyping of Mycobacterium tuberculosis. TB stigma has been described frequently, mainly in high-incidence settings, and is known to influence health-seeking behaviours and treatment adherence. The findings in this report highlight that TB-associated stigma may also lead to incomplete contact investigations. Little is known about the causes and impact of TB-related stigma in low-incidence countries and this warrants further exploration. Research is also needed to evaluate the effectiveness of specific interviewing techniques and training interventions for staff in reducing feelings of stigma in TB patients. Finally, the outbreak emphasizes the importance of integrating routine contact investigations with genotyping.

Acid suppressive agents and risk of Mycobacterium tuberculosis: case-control study

Background

The acid-suppressive agents have been linked with an increased risk of infectious disease. The relationship between these drugs and Mycobacterium Tuberculosis (TB) was not been reported.

Methods

We conducted a case–control study using data from National Health Insurance research database of Taiwan. From 1996 till 2008, and 6541 cases were defined as TB infection/activation (ICD-9 coding plus prescription two of four first-line anti-TB regimen for at least one month). Control subjects who were matched to the TB cases by age and sex were selected with 10:1 ratio. Medical records including acid-suppressive agent prescription and comorbidity, and socioeconomic status were analyzed.

Results

TB infection/activation was more frequent to comorbidity with chronic diseases, alcohol abuse, malignancy, immune deficient/suppression status and acid-related disease (peptic ulcer, reflux esophagitis). Among the TB cases, there was higher exposure record to acid-suppressive agents within 3 months before TB index date (OR 2.43(2.06-2.88) and 1.90 (1.68-2.14) for proton pump inhibitor (PPI) and histamine 2 receptor antagonist (H₂RA) respectively). After adjusting confounding factors, PPIs prescription 3 months before TB index date had an association of TB infection/activation (adjusted OR 1.63(1.61-1.63)). Similar result was found in H₂RA user (adjusted OR 1.51(1.50-1.52)). The association of acid-suppressive agents in TB infection/activation was fade gradually when the drug prescription period extended.

Conclusions

Recent prescription of acid-suppressive agent seems to associate the TB infection/activation. In the society where TB was prevalent, evaluation of pulmonary TB before prescription of PPI or H₂RA is warranted.

Tuberculosis: which patients do not identify their contacts?

SETTING

It is not known what the magnitude of non-identified TB contacts is in our country, or the reasons why contacts at risk are not identified.

OBJECTIVE

The purpose of this study was to analyze the determinants associated with non-identification of contacts.

DESIGN

This cross-sectional study included all cases of pulmonary tuberculosis diagnosed and treated in the Chest Disease Centre of Vila Nova de Gaia and their contacts, from 1st January to 31st December 2010. It included information collected from patients related to the identification of contacts in risk, and the information collected by the Public Health Unit during home, work and social places visits.

RESULTS

During the period of study, 61 cases of pulmonary TB were diagnosed: 41 cases (67.2%) identified all their contacts and 20 cases (32.8%) did not. 646 contacts were identified: 154 (23.8%) were identified only by the Public Health Unit (mean age of 40.67), and 492 (76.2%) were identified by the index cases (mean age of 33.25), (p=0.001). A mean of 10.59 contacts were identified per index case, of which, 83 (19.3%) screened positive. From those identified by the Public Health Unit, 10 (9.8%) had LTBI and 5 (4.9%) had active TB, and by the index case 61 (18.6%) had LTBI and 7 (2.1%) had active TB (crude OR=1.52; CI=0.83-2.79). The multivariate analysis showed that employment (adjusted OR=4.82; 95%CI=1.71-13.54) was associated to non-identification of contacts and patients preferably tended to identify relatives and co-habitants (adjusted OR=0.22; 95%CI=0.10-0.47).

CONCLUSION

TB patients tend to identify relatives and co-habitant contacts; contact at place of employment was found to be an independent risk factor for not being identified.

Delayed diagnosis and associated factors among new pulmonary tuberculosis patients diagnosed at the emergency department of a tertiary care hospital in Porto Alegre, South Brazil: a prospective patient recruitment study

Background

Control of tuberculosis (TB) depends on early diagnosis and treatment at the primary health care level. However, many patients are still diagnosed late with TB at hospitals. The present study aimed to investigate the delay in diagnosis of TB patients at the emergency department.

Methods

This was a prospective study in a general, tertiary care, university-affiliated hospital of a city with a high prevalence of TB in Brazil. New TB patients ≥ 14 years diagnosed with pulmonary TB at the emergency department of Hospital de Clínicas de Porto Alegre were prospectively recruited between February 2010 and January 2012. The consenting patients meeting our inclusion criteria were interviewed using a pre-tested questionnaire. We evaluated the delay in time until diagnosis and identified factors associated with delayed diagnosis (patient and health care system delays).

Results

We included 153 patients. The median total time of delay, patient delay, and health care system delay were 60 (interquartile range [IQR]: 30–90.5 days), 30 (lQR: 7–60 days), and 18 (IQR: 9–39.5 days) days, respectively. The factors that were independently associated with patient delay (time ≥ 30 days) were crack (odds ratio [OR] = 4.88, p = 0.043) and cocaine (OR = 6.68, p = 0.011) use. The factors that were independently associated with health care system delay (time ≥ 18 days) were weight loss (OR = 2.76, p = 0.025), miliary pattern (OR = 5.33, p = 0.032), and fibrotic changes (OR = 0.12, p = 0.013) on chest X-ray.

Conclusions

Patient delay appears to be the main problem in this city with a high prevalence of TB in Brazil. The main factor associated with patient delay is drug abuse (crack and cocaine). Our study shows substance abuse programs need to be aware of control of TB, with health interventions focusing on TB education programs.

Risk factors for tuberculosis

The risk of progression from exposure to the tuberculosis bacilli to the development of active disease is a two-stage process governed by both exogenous and endogenous risk factors. Exogenous factors play a key role in accentuating the progression from exposure to infection among which the bacillary load in the sputum and the proximity of an individual to an infectious TB case are key factors. Similarly endogenous factors lead in progression from infection to active TB disease. Along with well-established risk factors (such as human immunodeficiency virus (HIV), malnutrition, and young age), emerging variables such as diabetes, indoor air pollution, alcohol, use of immunosuppressive drugs, and tobacco smoke play a significant role at both the individual and population level. Socioeconomic and behavioral factors are also shown to increase the susceptibility to infection. Specific groups such as health care workers and indigenous population are also at an increased risk of TB infection and disease. This paper summarizes these factors along with health system issues such as the effects of delay in diagnosis of TB in the transmission of the bacilli.

"Shotgunning" in a population of patients with severe mental illness and comorbid substance use disorders

"Shotgunning" refers to the practice of one individual forcibly exhaling smoke into the mouth of another, and may increase the risk of transmission of respiratory pathogens. The extent of shotgunning among individuals with co-occurring serious mental illness and substance use is unknown. We included questions about shotgunning in an interview of 236 participants of a study testing a model to prevent and treat HIV and hepatitis. Shotgunning was common (61% [145/236]) and correlated with increased substance use severity and several high-risk behaviors. Only 8% (11/145) understood that shotgunning could transmit disease. Further research and patient education on shotgunning is warranted.

Tuberculosis outbreak investigations in the United States, 2002-2008

To understand circumstances of tuberculosis transmission that strain public health resources, we systematically reviewed Centers for Disease Control and Prevention (CDC) staff reports of US outbreaks in which CDC participated during 2002–2008 that involved >3 culture-confirmed tuberculosis cases linked by genotype and epidemiology. Twenty-seven outbreaks, representing 398 patients, were reviewed. Twenty-four of the 27 outbreaks involved primarily US-born patients; substance abuse was another predominant feature of outbreaks. Prolonged infectiousness because of provider- and patient-related factors was common. In 17 outbreaks, a drug house was a notable contributing factor. The most frequently documented intervention to control the outbreak was prioritizing contacts according to risk for infection and disease progression to ensure that the highest risk contacts were completely evaluated. US-born persons with reported substance abuse most strongly characterized the tuberculosis outbreaks in this review. Substance abuse remains one of the greatest challenges to controlling tuberculosis transmission in the United States.

Genotyping of Mycobacterium tuberculosis: application in epidemiologic studies

Genotyping is used to track specific isolates of Mycobacterium tuberculosis in a community. It has been successfully used in epidemiologic research (termed 'molecular epidemiology') to study the transmission dynamics of TB. In this article, we review the genetic markers used in molecular epidemiologic studies including the use of whole-genome sequencing technology. We also review the public health application of molecular epidemiologic tools.

Modelling the performance of isoniazid preventive therapy for reducing tuberculosis in HIV endemic settings: the effects of network structure

Individuals living with HIV experience a much higher risk of progression from latent M. tuberculosis infection to active tuberculosis (TB) disease relative to individuals with intact immune systems. A several-month daily course of a single drug during latent infection (i.e. isoniazid preventive therapy (IPT)) has proved in clinical trials to substantially reduce an HIV-infected individual's risk of TB disease. As a result of these findings and ongoing studies, the World Health Organization has produced strong guidelines for implementing IPT on a community-wide scale for individuals with HIV at risk of TB disease. To date, there has been limited use of IPT at a community-wide level. In this paper, we present a new co-network model for HIV and TB co-epidemics to address questions about how the population-level impact of community-wide IPT may differ from the individual-level impact of IPT offered to selected individuals. In particular, we examine how the effect of clustering of contacts within high-TB incidence communities may affect the rates of re-infection with TB and how this clustering modifies the expected population-level effects of IPT. We find that populations with clustering of respiratory contacts experience aggregation of TB cases and high numbers of re-infection events. While, encouragingly, the overall population-level effects of community-wide IPT appear to be sustained regardless of network structure, we find that in populations where these contacts are highly clustered, there is dramatic heterogeneity in the impact of IPT: in some sub-regions of these populations, TB is nearly eliminated, while in others, repeated re-infection almost completely undermines the effect of IPT. Our findings imply that as IPT programmes are brought to scale, we should expect local heterogeneity of effectiveness as a result of the complex patterns of disease transmission within communities.

Clustering of Mycobacterium tuberculosis cases in Acapulco: Spoligotyping and risk factors

Recurrence and reinfection of tuberculosis have quite different implications for prevention. We identified 267 spoligotypes of Mycobacterium tuberculosis from consecutive tuberculosis patients in Acapulco, Mexico, to assess the level of clustering and risk factors for clustered strains. Point cluster analysis examined spatial clustering. Risk analysis relied on the Mantel Haenszel procedure to examine bivariate associations, then to develop risk profiles of combinations of risk factors. Supplementary analysis of the spoligotyping data used SpolTools. Spoligotyping identified 85 types, 50 of them previously unreported. The five most common spoligotypes accounted for 55% of tuberculosis cases. One cluster of 70 patients (26% of the series) produced a single spoligotype from the Manila Family (Clade EAI2). The high proportion (78%) of patients infected with cluster strains is compatible with recent transmission of TB in Acapulco. Geomatic analysis showed no spatial clustering; clustering was associated with a risk profile of uneducated cases who lived in single-room dwellings. The Manila emerging strain accounted for one in every four cases, confirming that one strain can predominate in a hyperendemic area.

Why is in-hospital diagnosis of pulmonary tuberculosis delayed in southern Taiwan?

BACKGROUND/PURPOSE

In-hospital diagnosis delay (IHDD) of pulmonary tuberculosis (TB) has a significant impact on nosocomial TB transmission. We investigated the risk factors associated with prolonged IHDD in Taiwan, a high-resource, mid-incidence area.

METHODS

Between January 2005 and August 2006, we retrospectively enrolled 193 consecutive hospitalized patients. All of them had culture-proven pulmonary TB and did not receive antitubercular treatment at admission. IHDD was defined as the interval between admission and initiation of antitubercular treatment. Patients were grouped according to the median value of IHDD.

RESULTS

The median IHDD was 7 days. Patients with IHDD > 7 days were considered the prolonged-delay group, and those with IHDD <or= 7 days, the short-delay group. Independent risk factors [with adjusted odd ratios (95% confidence intervals)] for prolonged IHDD were: negative sputum smear [47.53 (13.20-171.18), p < 0.001]; non-cavitary lesions on chest radiographs [14.90 (3.46-64.14), p < 0.001]; admission to hospital departments other than chest medicine/infectious diseases [6.60 (1.95-22.41), p = 0.002]; exposure to fluoroquinolones before antitubercular treatment [5.29 (1.13-24.75), p = 0.034]; underlying malignancy [4.59 (1.13-18.67), p = 0.033); and age > 65 years [3.19 (1.01-10.05), p = 0.048]. Death attributed to tuberculosis was associated with positive sputum smear (hazard ratio = 21.85; 95% CI = 2.74-174.44; p = 0.004) but not prolonged IHDD (p = 0.325).

CONCLUSION

To minimize IHDD, clinicians should carefully manage hospitalized patients with risk factors for prolonged delay, such as those with negative sputum smears, non-cavitary lesions on chest radiographs, admission to departments other than chest medicine/infectious diseases, exposure to fluoroquinolones before antitubercular treatment, underlying malignancy, and age > 65 years.

Tuberculosis transmission and use of methamphetamines in Snohomish County, WA, 1991-2006

OBJECTIVES

We investigated a cluster of tuberculosis (TB) cases among persons using methamphetamines in Snohomish County, Washington, to determine the extent of the outbreak, examine whether methamphetamine use contributed to TB transmission, and implement strategies to prevent further infections.

METHODS

We screened contacts to find and treat persons with TB disease or infection. We then formed a multidisciplinary team to engage substance abuse services partners and implement outreach strategies including novel methods for finding contacts and a system of incentives and enablers to promote finding, screening, and treating patients with TB and their infected contacts.

RESULTS

We diagnosed and completed treatment with 10 persons with TB disease. Eight of 9 adult patients and 67% of their adult contacts reported using methamphetamines. Of the 372 contacts, 319 (85.8%) were screened, 80 (25.1%) were infected, 71 (88.8%) started treatment for latent infection, and 57 (80.3%) completed treatment for latent infection.

CONCLUSIONS

Collaborative approaches integrating TB control, outreach, incentives, and enablers resulted in high rates of treatment adherence and completion among patients and infected contacts. TB control programs should collaborate with substance abuse programs to address addiction, overcome substance abuse-related barriers to treatment, treat TB, and prevent ongoing transmission.

A Mycobacterium tuberculosis cluster demonstrating the use of genotyping in urban tuberculosis control

Background

DNA fingerprinting of Mycobacterium tuberculosis isolates offers better opportunities to study links between tuberculosis (TB) cases and can highlight relevant issues in urban TB control in low-endemic countries.

Methods

A medium-sized molecular cluster of TB cases with identical DNA fingerprints was used for the development of a visual presentation of epidemiologic links between cases.

Results

Of 32 cases, 17 (53%) were linked to the index case, and 11 (34%) to a secondary case. The remaining four (13%) could not be linked and were classified as possibly caused by the index patient. Of the 21 cases related to the index case, TB developed within one year of the index diagnosis in 11 patients (52%), within one to two years in four patients (19%), and within two to five years in six patients (29%).

Conclusion

Cluster analysis underscored several issues for TB control in an urban setting, such as the recognition of the outbreak, the importance of reinfections, the impact of delayed diagnosis, the contribution of pub-related transmissions and its value for decision-making to extend contact investigations. Visualising cases in a cluster diagram was particularly useful in finding transmission locations and the similarities and links between patients.

Delayed tuberculosis treatment in urban and suburban Ontario

BACKGROUND

Delay in the treatment of patients with tuberculosis (TB) increases the risk of poor clinical outcomes--including death and transmission of disease--and may be reducible.

OBJECTIVE

To estimate delays in TB treatment in a Canadian, multicultural population and to examine factors associated with longer time to treatment.

METHODS

Adult cases of active TB from January 1998 to December 2001 from the Ontario Reportable Disease Information System were included. Time to treatment was defined as the number of days between symptom onset and treatment.

RESULTS

Data from 1753 TB patients (76% of eligible patients) were analyzed. Median time to treatment was 62 days (interquartile range 31 to 114 days). Time periods longer than the median time to treatment were independently associated with middle-aged patients (OR 1.54, 95% CI 1.21 to 1.98), foreign-born patients who had lived in Canada for more than 10 years (OR 1.47, 95% CI 1.02 to 2.12), patients with nonpulmonary disease (OR 1.57, 95% CI 1.28 to 1.92) and patients managed within certain health districts.

CONCLUSION

A time to TB treatment of two months or more is common in Ontario, and associated with several factors. Future studies are needed to build on these findings to decrease delay and improve individual and public health outcomes.

Transmission classification model to determine place and time of infection of tuberculosis cases in an urban area

We conducted a population-based study in the Rotterdam region of The Netherlands to determine the place and time of infection of tuberculosis (TB) cases using conventional epidemiological and genotyping information. In particular, we focused on the extent of misclassification if genotyping was not combined with epidemiological information. Cases were divided into those with a unique mycobacterial DNA fingerprint, a clustering fingerprint, and an unknown fingerprint. We developed transmission classification trees for each category to determine whether patients were infected in a foreign country or recently (<or=2 years) or remotely (>2 years) infected in The Netherlands. Of all TB cases during the 12-year study period, 38% were infected in a foreign country, 36% resulted from recent transmission in The Netherlands, and 18% resulted from remote infection in The Netherlands, while in the remaining cases (9%) either the time or place of infection could not be determined. The conventional epidemiological data suggested that at least 29% of clustered cases were not part of recent chains of transmission. Cases with unknown fingerprints, almost all culture negative, relatively frequently had confirmed epidemiological links with a recent pulmonary TB case in The Netherlands and were more often identified by contact tracing. Our findings highlight the idea that genotyping should be combined with conventional epidemiological investigation to establish the place and time of infection of TB cases as accurately as possible. A standardized way of classifying TB into recently, remotely, and foreign-acquired disease provides indicators for surveillance and TB control program performance that can be used to decide on interventions and allocation of resources.

Diagnosing latent tuberculosis infection in the HIV era

Tuberculin skin testing (TST) and Interferon-gamma (IFNγ)release assays (IGRAs) are presently the only available assays for the detection of Mycobacterium tuberculosis infected individuals. IGRAs might progressively replace TST, as numerous published reports establish their higher specificity and similar sensitivity when tested in BCG vaccinated, immunocompetent individuals or in populations who may have been in contact with atypical mycobacteria. However, few published reports have commented on their role in TB diagnosis in immunocompromised individuals (HIV, immunosuppressive therapy, cancer…). It is the purpose of this report to review IGRAs published studies in HIV individuals in endemic and non endemic area for tuberculosis (TB). IGRAs were tested in the presence or absence of active TB but correlated to duration of exposure. In newly diagnosed active TB, IGRAs demonstrated a similar sensitivity to TST. In TB non infected individuals, TST and IGRAs also gave similar values when categorization of individuals was correlated to the risk of infection. A higher number of positive IGRAs was observed in individuals from TB endemic areas, in similar proportions to immunocompetent individuals. Comparison between the two IGRAs: QuantiFERON-TB Gold^® (QF-TB, Cellestis, Australia) and T-SPOT-TB^® (Oxford Immunotec, UK), and against TST, in the same HIV population demonstrates a higher sensitivity of T-SPOT-TB and TST than QF-TB. Indeterminate results, which correspond to the absence of a positive T-cell IFNγ response towards phytohemaglutinin (PHA), is a key point when comparing both IGRAs. This PHA control is indicative of the level of immunosuppression observed in the tested individual. QF-TB seems to present, in HIV populations, more indeterminate results than T-SPOT-TB. The calibration and/or concentration of PBMC on nitrocellulose membrane for the T-SPOT-TB, as compared to a whole blood assay, might explain this difference, with less indeterminate results with the T-SPOT-TB assay. Neither assay is able to differentiate active TB from latent TB infection (LTBI). Several laboratories have tried new antigenic epitopes to solve this issue. It is of importance that these studies need to be repeated on a larger scale by others to validate their results. Two blood assays might add information characterising the evolution from LTBI to active TB: either by losing protective immunity, as demonstrated by the whole blood killing assay, or by evaluating the kinetics of the antibodies synthesized against M. tuberculosis specific antigens. In conclusion, longitudinal studies are still needed to validate IGRAs and other assays and to define their respective predictive values.

Knowledge of tuberculosis transmission among recently infected patients in Glasgow

OBJECTIVES

To examine perceptions and understanding of disease causation in tuberculosis patients with few epidemiological links detected by contact tracing.

STUDY DESIGN

An exploratory qualitative study using semi-structured interviews was undertaken. Patients' beliefs were explored against a background of medical thinking about tuberculosis transmission and the current approach to contact tracing.

METHODS

Interviews were undertaken with patients (n=23) or suitable next of kin (n=3). Study patients were diagnosed with tuberculosis in Glasgow, an urban area of Scotland, between 1997 and 2004. All had a genetically indistinguishable 15-banded IS6110 restriction fragment length polymorphism pattern of the Beijing family of Mycobacterium tuberculosis, suggestive of recently transmitted infection, yet few had epidemiological links detectable as a result of contact tracing (30.8%).

RESULTS

Interviewees had varying levels of knowledge, but most believed that tuberculosis was caused by a pathogen, spread by person-to-person contact. Modes of transmission were thought to include airborne transmission, sharing utensils with an infected individual, consumption of contaminated foods/liquids, and exchange of bodily fluids. Prolonged contact was not thought to be required for transmission to occur. Impaired immunity, social factors and environmental factors were believed to enhance the potential for transmission.

CONCLUSIONS

Patients have complex beliefs about tuberculosis transmission and causation, which do not always mirror those of health professionals. Adopting and implementing an approach to contact identification that is aligned with lay beliefs may result in improved contact tracing outcomes.

An ecological study of tuberculosis transmission in California

OBJECTIVES

We evaluated the association between ecological factors and rates of tuberculosis within California, using pediatric tuberculosis as an indicator of new transmission.

METHODS

Ecological variables such as racial/ethnic distribution, immigration level, education, employment, poverty, and crowding were obtained from the United States Census for each census tract in California. These data were incorporated into a negative binomial regression model with the rate of pediatric tuberculosis disease in each census tract as an outcome variable. Disease rates were obtained by geocoding reported cases. Subsections of the state (San Francisco and Los Angeles) were examined independently.

RESULTS

Census tracts with lower median incomes, more racial/ethnic minorities, and more immigrants had higher rates of pediatric tuberculosis. Other frequently cited risk factors such as overcrowding and unemployment were not associated with increased disease after adjusting for other measures. Risks were comparable across regions, but subtle differences were noted.

CONCLUSIONS

The techniques used in this work provide a way to examine a disease within its social context. The results confirmed that tuberculosis in California continues to be a disease of poverty and racial/ethnic minorities.

Increased reported cases of tuberculosis among children younger than 5 years of age, Maricopa County, Arizona, 2002-2003

OBJECTIVES

Although tuberculosis (TB) rates in the United States among children younger than 5 years old (2.8/100,000 in 2003) have been declining, Maricopa County, Arizona, reported an increase from 4.1/100,000 in 2002 to 9.0/100,000 in 2003. We investigated factors associated with this increase.

METHODS

We reviewed county TB clinic records of pediatric patients (younger than 5 years old) and their probable adult sources, interviewed parents or guardians of pediatric TB patients and examined changes in clinic procedures.

RESULTS

We verified 11 pediatric TB cases in 2002 and 25 in 2003 (n = 36). A total of 31 (86%) patients were born in the United States, and 28 (78%) had at least 1 foreign-born parent. There were 19 children (53%) identified from an adult TB contact investigation. Of children with identified sources (n = 24, 67%), 23 (96%) had probable household transmission; 20 (83%) had a foreign-born relative from a TB-endemic country as the probable source. Seven (50%) of 14 adult sources investigated had a delayed TB diagnosis. In 2003, increased TB clinic staffing, more frequent pediatric TB clinics and on-site gastric aspirates for TB diagnosis contributed to 55% more children being evaluated for TB.

CONCLUSIONS

Close interaction with family members and delayed diagnoses were the primary means of TB transmission to children. The increase in pediatric TB likely reflects improved clinic diagnostic capacity and may indicate a more accurate baseline rate for Maricopa County. Programmatic improvements in TB control and targeted outreach to high-risk immigrant populations may increase pediatric and adult source case detection and reduce Mycobacterium tuberculosis transmission.

Occupational Medicine Forum

The Occupational Medicine Forum is prepared by the ACOEM Occupational and Environmental Medical Practice Committee and does not necessarily represent an official ACOEM position. The Forum is intended for health professionals and is not intended to provide medical or legal advice, including illness prevention, diagnosis or treatment, or regulatory compliance. Such advice should be obtained directly from a physician and/or attorney.

American Thoracic Society/Centers for Disease Control and Prevention/Infectious Diseases Society of America: Controlling Tuberculosis in the United States

During 1993-2003, incidence of tuberculosis (TB) in the United States decreased 44% and is now occurring at a historic low level (14,874 cases in 2003). The Advisory Council for the Elimination of Tuberculosis has called for a renewed commitment to eliminating TB in the United States, and the Institute of Medicine has published a detailed plan for achieving that goal. In this statement, the American Thoracic Society (ATS), Centers for Disease Control and Prevention (CDC), and the Infectious Diseases Society of America (IDSA) propose recommendations to improve the control and prevention of TB in the United States and to progress toward its elimination. This statement is one in a series issued periodically by the sponsoring organizations to guide the diagnosis, treatment, control, and prevention of TB. This statement supersedes the previous statement by ATS and CDC, which was also supported by IDSA and the American Academy of Pediatrics (AAP). This statement was drafted, after an evidence-based review of the subject, by a panel of representatives of the three sponsoring organizations. AAP, the National Tuberculosis Controllers Association, and the Canadian Thoracic Society were also represented on the panel. This statement integrates recent scientific advances with current epidemiologic data, other recent guidelines from this series, and other sources into a coherent and practical approach to the control of TB in the United States. Although drafted to apply to TB-control activities in the United States, this statement might be of use in other countries in which persons with TB generally have access to medical and public health services and resources necessary to make a precise diagnosis of the disease; achieve curative medical treatment; and otherwise provide substantial science-based protection of the population against TB. This statement is aimed at all persons who advocate, plan, and work at controlling and preventing TB in the United States, including persons who formulate public health policy and make decisions about allocation of resources for disease control and health maintenance and directors and staff members of state, county, and local public health agencies throughout the United States charged with control of TB. The audience also includes the full range of medical practitioners, organizations, and institutions involved in the health care of persons in the United States who are at risk for TB.

[Epidemiological survey of a suspected nosocomial case of tuberculosis by spoligotyping]

Transmission of tuberculosis within hospitals has been increasingly recognized as a hazard for patients and health care workers. A case of pulmonary tuberculosis was detected in September 2003 in a nursing auxiliary working at Avicenne's Hospital. This 49 year-old woman was considered infected since April 2003. During this 6 months period, she worked in 23 distinct hospital units and could have contaminated patients and hospital staffs. The epidemiological survey was comprised for 1735 individuals (701 hospital staffs and 1034 patients). It encompassed clinical, para-clinical investigations and bacteriological investigations. Furthermore, between January 2003 and September 2004, a systematic comparison of 62 Mycobacterium tuberculosis strains isolated in the hospital was conducted by spoligotyping, a molecular typing method in order to access an eventual transmission. The nursing auxiliary's strain clearly showed a distinct spoligotype from the other investigated strains. This spoligotype was unique in the international spoligotype database. In this large epidemiological survey of a case of suspected nosocomial of tuberculosis, spoligotyping appeared as an interesting, easy and rapid method of molecular typing. It allowed to demonstrate that the nursing auxiliary tuberculosis case was unrelated to the others cases of tuberculosis diagnosed in the hospital during this period.

Molecular Epidemiology: A Tool for Understanding Control of Tuberculosis Transmission

One of the primary goals of tuberculosis control programs is to interrupt the transmission of Mycobacterium tuberculosis. The development of several genotyping tools has allowed tracking of strains of M. tuberculosis as they spread through communities. Studies that have combined the use of genotyping with conventional epidemiologic investigation have increased the understanding of the transmission and pathogenesis of tuberculosis. This article reviews some of the lessons learned using these new epidemiologic tools.

Unsuspected Recent Transmission of Tuberculosis among High-Risk Groups: Implications of Universal Tuberculosis Genotyping in Its Detection

BACKGROUND

The initiation of universal genotyping revealed 3 clusters of 19 patients with tuberculosis (TB) in Wisconsin, with no apparent epidemiologic links among most of them. An epidemiologic investigation was conducted to determine whether genotype clustering resulted from recent transmission.

METHODS

We conducted additional interviews with patients and reviewed medical records. Places frequented by the patients while they were infectious were visited to identify contacts.

RESULTS

Our investigation revealed several previously unrecognized possible sites of TB transmission: a single-room occupancy hotel, 2 homeless shelters, 1 bar, and 2 crack houses. Seven patients with previously diagnosed TB were added to the clusters. Of 26 patients, we identified epidemiologic links for all but 1. Common risk factors among patients included alcohol abuse, crack cocaine use, homelessness, and unemployment. Additionally, 98 contacts missed during routine contact investigation were identified.

CONCLUSIONS

Transmission of TB, particularly among high-risk groups, may go undetected for years. Our investigation demonstrated the value of universal genotyping in revealing unsuspected recent TB transmission and previously unrecognized sites of transmission, which can be targeted for specific TB interventions.

Using GIS technology to identify areas of tuberculosis transmission and incidence

Background

Currently in the U.S. it is recommended that tuberculosis screening and treatment programs be targeted at high-risk populations. While a strategy of targeted testing and treatment of persons most likely to develop tuberculosis is attractive, it is uncertain how best to accomplish this goal. In this study we seek to identify geographical areas where on-going tuberculosis transmission is occurring by linking Geographic Information Systems (GIS) technology with molecular surveillance.

Methods

This cross-sectional analysis was performed on data collected on persons newly diagnosed with culture positive tuberculosis at the Tarrant County Health Department (TCHD) between January 1, 1993 and December 31, 2000. Clinical isolates were molecularly characterized using IS6110-based RFLP analysis and spoligotyping methods to identify patients infected with the same strain. Residential addresses at the time of diagnosis of tuberculosis were geocoded and mapped according to strain characterization. Generalized estimating equations (GEE) analysis models were used to identify risk factors involved in clustering.

Results

Evaluation of the spatial distribution of cases within zip-code boundaries identified distinct areas of geographical distribution of same strain disease. We identified these geographical areas as having increased likelihood of on-going transmission. Based on this evidence we plan to perform geographically based screening and treatment programs.

Conclusion

Using GIS analysis combined with molecular epidemiological surveillance may be an effective method for identifying instances of local transmission. These methods can be used to enhance targeted screening and control efforts, with the goal of interruption of disease transmission and ultimately incidence reduction.

Relating the size of molecularly defined clusters of tuberculosis to the duration of symptoms

Molecular profiling of Mycobacterium tuberculosis isolates has improved recognition of tuberculosis case clusters, but the determinants of cluster size are unknown. We hypothesized that longer duration of symptoms prior to initiation of tuberculosis therapy would be associated with increased cluster size. All patients with tuberculosis in Harris County, Texas, identified between 10/1/95 and 12/31/97 through a prospective population-based project were interviewed, had their medical records reviewed, and had M. tuberculosis isolates molecularly characterized. There were 506 symptomatic, evaluable patients in 74 clusters, ranging in size from 2 patients (32 clusters) to 61 patients (1 cluster). The median duration of symptoms was 46 days (range, 1-471 days). There was no association between the log-transformed duration of symptoms and cluster size in univariate or multivariate analysis. In multivariate analysis, age and HIV coinfection were inversely related to cluster size, but only weakly. The size of molecularly defined clusters of tuberculosis was not related to the duration of symptoms of most patients who belonged to clusters.

Molecular epidemiology of tuberculosis in a low- to moderate-incidence state: are contact investigations enough?

To assess the circumstances of recent transmission of tuberculosis (TB) (progression to active disease <2 years after infection), we obtained DNA fingerprints for 1172 (99%) of 1179 Mycobacterium tuberculosis isolates collected from Maryland TB patients from 1996 to 2000. We also reviewed medical records and interviewed patients with genetically matching M. tuberculosis strains to identify epidemiologic links (cluster investigation). Traditional settings for transmission were defined as households or close relatives and friends; all other settings were considered nontraditional. Of 436 clustered patients, 115 had recently acquired TB. Cluster investigations were significantly more likely than contact investigations to identify patients who recently acquired TB in nontraditional settings (33/42 vs. 23/72, respectively; p<0.001). Transmission from a foreign-born person to a U.S.-born person was rare and occurred mainly in public settings. The time from symptom onset to diagnosis was twice as long for transmitters as for nontransmitters (16.8 vs. 8.5 weeks, respectively; p<0.01). Molecular epidemiologic studies showed that reducing diagnostic delays can prevent TB transmission in nontraditional settings, which elude contact investigations.

Identifying the sources of tuberculosis in young children: a multistate investigation

To better understand the molecular epidemiology of tuberculosis (TB) transmission for culture-confirmed patients <5 years of age, data were analyzed from a population-based study conducted in seven U.S. sites from 1996 to 2000. Mycobacterium tuberculosis isolates were genotyped with IS6110-based restriction fragment length polymorphism analysis and spoligotyping. Case-patient data were obtained from the Centers for Disease Control and Prevention s national tuberculosis registry and health department records. Routine public health investigations conducted by local health departments identified suspected source patients for 57 (51%) of 111 culture-confirmed patients <5 years of age. For 8 (15%) of 52 culture-confirmed patients <5 years of age and their suspected source patients with complete genotyping results, genotypes suggested infection with different TB strains. Potential differences between sources for patients <5 years of age and source patients that transmitted TB to adolescent and adult patients were identified.

Tuberculosis contact investigation policies, practices, and challenges in 11 U.S. communities

To describe the policies and procedures used by 11 urban tuberculosis control programs to conduct contact investigations, written policies were reviewed and semistructured interviews were conducted with program managers and staff. Qualitative analysis showed that contact investigation policies and procedures vary widely. Most policies address risk factor assessment and contact prioritization; however, none of the policies provide comprehensive guidance for the entire process. Staffing patterns vary, but, overall, staff receive little formal training; informal monitoring practices predominate. Comprehensive guidelines and programmatic support are needed to improve the quality of contact investigation processes.

Transmission of Mycobacterium tuberculosis in a rural community, Arkansas, 1945-2000

A cluster of tuberculosis cases in a rural community in Arkansas persisted from 1991 to 1999. The cluster had 13 members, 11 linked epidemiologically. Old records identified 24 additional patients for 40 linked cases during a 54-year period. Residents of this neighborhood represent a population at high risk who should be considered for tuberculin testing and treatment for latent tuberculosis infection.

Transmission dynamics of tuberculosis in Tarrant county, Texas

To understand the transmission dynamics of tuberculosis in Tarrant County, Texas, we performed a population-based study of 159 patients with culture-proven tuberculosis, combining restriction fragment length polymorphism (RFLP) analysis of Mycobacterium tuberculosis isolates with prospective interviewing to identify epidemiologic links between patients. Patients whose isolates had identical or closely related RFLP patterns were considered a cluster. Seventy-six (48%) of 159 patients were in 19 clusters, suggesting that recent transmission accounted for 36% of tuberculosis morbidity. Unconditional logistic regression showed that birth in the United States, continuous residence in Tarrant County, a history of homelessness, and a history of visiting or working in bars were independent predictors of clustering. Four homeless shelters and five bars were associated with specific clusters, suggesting that they were sites of tuberculosis transmission. Patients in some clusters recognized more photographs of patients in their cluster than did patients outside their cluster. We conclude that (1) homeless shelters and bars are important sites of tuberculosis transmission in Tarrant County, and (2) the use of photograph recognition of patients with tuberculosis, in combination with RFLP analysis, has the potential to enhance tuberculosis control by facilitating identification of epidemiologic links between patients.

Sampling bias in the molecular epidemiology of tuberculosis

Among the goals of the molecular epidemiology of infectious disease are to quantify the extent of ongoing transmission of infectious agents and to identify host- and strain-specific risk factors for disease spread. I demonstrate the potential bias in estimates of recent transmission and the impact of risk factors for clustering by using computer simulations to reconstruct populations of tuberculosis patients and sample from them. The bias consistently results in underestimating recent transmission and the impact of risk factors for recent transmission.

Limited transmission of multidrug-resistant tuberculosis despite a high proportion of infectious cases in Los Angeles County, California

Preventing transmission of multidrug-resistant tuberculosis is critical because of treatment toxicity, cost, and the lack of effective therapy for latent infection. We attempted to determine the extent of transmission in Los Angeles County by comparing relatedness of multidrug-resistant tuberculosis cases using restriction fragment length polymorphism and by cross-matching contact information to the Tuberculosis Registry. Strain typing was done on isolates of 102 pulmonary multidrug-resistant cases identified between August 1993 and 1998. Seventy-one (70%) of the cases had cavitary lesions on chest radiograph, and 94 (92%) had sputa smear-positive for acid fast bacilli. Fifteen (15%) of the cases were known to be infected with human immunodeficiency virus. Four molecular clusters of two cases each and one closely related pair were identified among the 102 cases; contact investigation successfully identified all clusters but one. Among 946 contacts identified and cross-matched with the county's Tuberculosis Registry, one secondary case due to drug-resistant Mycobacterium bovis was found. To summarize, a very high proportion of pulmonary multidrug-resistant tuberculosis cases in Los Angeles County were infectious. Molecular strain typing indicated limited spread of disease, although it underestimated transmission compared with contact investigation. We believe aggressive surveillance and case management were critical to limiting the spread of multidrug- resistant tuberculosis.

Determinants of cluster distribution in the molecular epidemiology of tuberculosis

Recently developed molecular techniques have revolutionized the epidemiology of tuberculosis. Multiple studies have used these tools to examine the population structure of Mycobacterium tuberculosis isolates in different communities. The distributions of clusters of M. tuberculosis isolates in these settings may variously reflect social mixing patterns or the differential fitness of specific clones of the organism. We developed an individual-based microsimulation of tuberculosis transmission to explore social and demographic determinants of cluster distribution and to observe the effect of transmission dynamics on the empiric data from molecular epidemiologic studies. Our results demonstrate that multiple host-related factors contribute to wide variation in cluster distributions even when all strains of the organism are assumed to be equally transmissible. These host characteristics include interventions such as chemotherapy, vaccination and chemoprophylaxis, HIV prevalence, the age structure of the population, and the prevalence of latent tuberculosis infection. We consider the implications of these results for the interpretation of cluster studies of M. tuberculosis as well as the more general application of microsimulation models to infectious disease epidemiology.

Amplification dynamics: predicting the effect of HIV on tuberculosis outbreaks

HIV affects the pathogenesis and the transmission of Mycobacterium tuberculosis. We used a discrete event simulation model to predict the potential impact of HIV on increasing the probability and the expected severity of tuberculosis outbreaks. Our predictions reveal that an HIV epidemic can significantly increase the frequency and severity of tuberculosis outbreaks, but that this amplification effect of HIV on tuberculosis outbreaks is very sensitive to the tuberculosis treatment rate. At moderate or low treatment rates, even a moderate HIV epidemic can cause the average size of tuberculosis outbreaks to almost double in comparison with the expected outbreak size when HIV is absent. However, we determined that the amplification effect of HIV can be substantially reduced if the treatment rate of tuberculosis is very high. We discuss the significant implications of these results for the global control of tuberculosis. Our results also reveal that occasionally a "normal-virulence" strain of M. tuberculosis can be expected to generate a large outbreak. We discuss the implications of these results in understanding the virulence of M. tuberculosis and in the planned elimination of tuberculosis in the United States.

[Risk factors associated to tuberculosis patients with positive sputum microscopy]

OBJECTIVE

The main factor responsible for producing new cases of tuberculosis by exogen transmission is the existence of Mycobacterium tuberculosis in the sputum of tuberculosis patients. The objective of this study was to determine the risk factors associated to positive smear tuberculosis cases in Lleida (Spain).

METHODS

We studied new cases of tuberculosis over the period 1992-1998. The variables considered were: age, gender, coinfection with HIV, injection drug use (IDU), consumption of alcohol, existence of caverns in thorax X-ray, and laboratory results of direct smear examination. We calculated the incidence rates for 100,000 persons-year. The association between the dependent variable case of tuberculosis with positive Mycobacterium tuberculosis smear and the remaining independent variables were assessed obtaining odds ratios (OR) and 95% confidence intervals (CI) (crude cOR and adjusted aOR by non conditional logistic regression).

RESULTS

We detected 905 new cases of tuberculosis. The rates in the period 1992-1998 decreased from 38.8 to 30.8. 44.9% of cases (n = 406) presented a positive direct smear. There was a positive association between the risk of being a positive smear patient and having caverns in thorax x-ray (aOR = 6.8; 95% CI, 4.8-95), being male (aOR = 1.8; 95% CI, 1.3-2.6) and consuming alcohol (aOR = 1.6; 95% CI,1.1-2.3) and this risk was significant lower in those under 15 years old (aOR = 0.2; 95% CI, 0.1-0.5), and coinfection with HIV (aOR = 0.5; 95% CI, 0.3-0.9).

CONCLUSIONS

HIV infection implies a reduced impact in endemecity of tuberculosis. Study of contacts and the implementation of directly observed treatment must be considered not only for coinfected HIV cases and IDU but also for adult males, especially those who consume alcohol, particularly when they have caverns.

Tuberculosis in disadvantaged groups

Tuberculosis remains predominantly a disease of the disadvantaged and marginalized. The incidence of the disease is increasing in many industrially developed countries, particularly among the poor, ethnic minorities, prisoners and other institutionalized persons, and the socially isolated and hard to reach groups. Strengthening of the tuberculosis services is required to care for these groups. Millions of people in the developing nations are disadvantaged by poverty and inequity, and recent health sector reforms have not always been entirely in their interest. A further serious problem is the HIV/AIDS pandemic, which not only facilitates the spread of tuberculosis but, by its associated stigma, leads to delayed treatment seeking and poor adherence to therapy. In recent times, emphasis has moved away from didactic principles of tuberculosis "control" to community-and patient-centered health services, based on analysis of local factors affecting case finding and adherence to therapy.