A field-validated approach using surveillance and genotyping data to estimate tuberculosis attributable to recent transmission in the United States

Disparities in Tuberculosis Incidence by Race and Ethnicity Among the U.S.-Born Population in the United States, 2011 to 2021 : An Analysis of National Disease Registry Data

BACKGROUND

Elevated tuberculosis (TB) incidence rates have recently been reported for racial/ethnic minority populations in the United States. Tracking such disparities is important for assessing progress toward national health equity goals and implementing change.

OBJECTIVE

To quantify trends in racial/ethnic disparities in TB incidence among U.S.-born persons.

DESIGN

Time-series analysis of national TB registry data for 2011 to 2021.

SETTING

United States.

PARTICIPANTS

U.S.-born persons stratified by race/ethnicity.

MEASUREMENTS

TB incidence rates, incidence rate differences, and incidence rate ratios compared with non-Hispanic White persons; excess TB cases (calculated from incidence rate differences); and the index of disparity. Analyses were stratified by sex and by attribution of TB disease to recent transmission and were adjusted for age, year, and state of residence.

RESULTS

In analyses of TB incidence rates for each racial/ethnic population compared with non-Hispanic White persons, incidence rate ratios were as high as 14.2 (95% CI, 13.0 to 15.5) among American Indian or Alaska Native (AI/AN) females. Relative disparities were greater for females, younger persons, and TB attributed to recent transmission. Absolute disparities were greater for males. Excess TB cases in 2011 to 2021 represented 69% (CI, 66% to 71%) and 62% (CI, 60% to 64%) of total cases for females and males, respectively. No evidence was found to indicate that incidence rate ratios decreased over time, and most relative disparity measures showed small, statistically nonsignificant increases.

LIMITATION

Analyses assumed complete TB case diagnosis and self-report of race/ethnicity and were not adjusted for medical comorbidities or social determinants of health.

CONCLUSION

There are persistent disparities in TB incidence by race/ethnicity. Relative disparities were greater for AI/AN persons, females, and younger persons, and absolute disparities were greater for males. Eliminating these disparities could reduce overall TB incidence by more than 60% among the U.S.-born population.

PRIMARY FUNDING SOURCE

Centers for Disease Control and Prevention.

Asynchronous Video Directly Observed Therapy to Monitor Short-Course Latent Tuberculosis Infection Treatment: Results of a Randomized Controlled Trial

Background

Observing medication ingestion through self-recorded videos (video directly observed therapy [VDOT]) has been shown to be a cost-effective alternative to in-person directly observed therapy (DOT) for monitoring adherence to treatment for tuberculosis disease. VDOT could be a useful tool to monitor short-course latent tuberculosis infection (LTBI) treatment.

Methods

We conducted a prospective randomized controlled trial comparing VDOT (intervention) and clinic-based DOT (control) among patients newly diagnosed with LTBI who agreed to a once-weekly 3-month treatment regimen of isoniazid and rifapentine. Study outcomes were treatment completion and patient satisfaction. We also assessed costs. Pre- and posttreatment interviews were conducted.

Results

Between March 2016 and December 2019, 130 participants were assigned to VDOT (n = 68) or DOT (n = 62). Treatment completion (73.5% vs 69.4%, P = .70) and satisfaction with treatment monitoring (92.1% vs 86.7%, P = .39) were slightly higher in the intervention group than the control group, but neither was statistically significant. VDOT cost less per patient (median, $230; range, $182-$393) vs DOT (median, $312; range, $246-$592) if participants used their own smartphone.

Conclusions

While both groups reported high treatment satisfaction, VDOT was not associated with higher LTBI treatment completion. However, VDOT cost less than DOT. Volunteer bias might have reduced the observed effect since patients opposed to any treatment monitoring could have opted for alternative unobserved regimens. Given similar outcomes and lower cost, VDOT may be useful for treatment monitoring when in-person observation is prohibited or unavailable (eg, during a respiratory disease outbreak). The trial was registered at the National Institutes of Health (ClinicalTrials.gov NTC02641106).

Clinical Trials Registration

ClinicalTrials.gov NTC02641106; registered 24 October 2016.

Estimated rates of progression to tuberculosis disease for persons infected with Mycobacterium tuberculosis in the United States

BACKGROUND

In the United States, over 80% of tuberculosis (TB) disease cases are estimated to result from reactivation of latent TB infection (LTBI) acquired more than 2 years previously ("reactivation TB"). We estimated reactivation TB rates for the US population with LTBI, overall, by age, sex, race-ethnicity, and US-born status, and for selected comorbidities (diabetes, end-stage renal disease, and HIV).

METHODS

We collated nationally representative data for 2011-2012. Reactivation TB incidence was based on TB cases reported to the National TB Surveillance System that were attributed to LTBI reactivation. Person-years at risk of reactivation TB were calculated using interferon-gamma release assay (IGRA) positivity from the National Health and Nutrition Examination Survey, published values for interferon-gamma release assay sensitivity and specificity, and population estimates from the American Community Survey.

RESULTS

For persons aged ≥6 years with LTBI, the overall reactivation rate was estimated as 0.072 (95% uncertainty interval: 0.047, 0.12) per 100 person-years. Estimated reactivation rates declined with age. Compared to the overall population, estimated reactivation rates were higher for persons with diabetes (adjusted rate ratio [aRR] = 1.6 [1.5, 1.7]), end-stage renal disease (aRR = 9.8 [5.4, 19]), and HIV (aRR = 12 [10, 13]).

CONCLUSIONS

In our study, individuals with LTBI faced small, non-negligible risks of reactivation TB. Risks were elevated for individuals with medical comorbidities that weaken immune function.

Using Geographic Disaggregation to Compare Tuberculosis Epidemiology Among American Indian and Alaska Native Persons-USA, 2010-2020

BACKGROUND

American Indian and Alaska Native (AIAN) populations are frequently associated with the highest rates of tuberculosis (TB) disease of any racial/ethnic group in the USA. We systematically investigated variation in patterns and potential drivers of TB epidemiology among geographically distinct AIAN subgroups.

METHODS

Using data reported to the National Tuberculosis Surveillance System during 2010-2020, we applied a geographic method of data disaggregation to compare annual TB incidence and the frequency of TB patient characteristics among AIAN persons in Alaska with AIAN persons in other states. We used US Census data to compare the prevalence of substandard housing conditions in AIAN communities in these two geographic areas.

RESULTS

The average annual age-adjusted TB incidence among AIAN persons in Alaska was 21 times higher than among AIAN persons in other states. Compared to AIAN TB patients in other states, AIAN TB patients in Alaska were associated with significantly higher frequencies of multiple epidemiologic TB risk factors (e.g., attribution of TB disease to recent transmission, previous diagnosis of TB disease) and significantly lower frequencies of multiple clinical risk factors for TB disease (e.g., diagnosis with diabetes mellitus, end-stage renal disease). Occupied housing units in AIAN communities in Alaska were associated with significantly higher frequencies of multiple measures of substandard housing conditions compared to AIAN communities in other states.

CONCLUSIONS

Observed differences in patient characteristics and substandard housing conditions are consistent with contrasting syndromes of TB epidemiology in geographically distinct AIAN subgroups and suggest ways that associated public health interventions could be tailored to improve efficacy.

Racial and Ethnic Disaggregation of Tuberculosis Incidence and Risk Factors Among American Indian and Alaska Native Persons-United States, 2001-2020

Objectives. To examine impacts of racial and ethnic disaggregation on the characterization of tuberculosis (TB) epidemiology among American Indian and Alaska Native (AI/AN) persons in the United States. Methods. Using data reported to the National Tuberculosis Surveillance System during 2001 to 2020, we compared annual age-adjusted TB incidence and the frequency of TB risk factors among 3 AI/AN analytic groups: non-Hispanic AI/AN alone persons, multiracial/Hispanic AI/AN persons, and all AI/AN persons (aggregate of the first 2 groups). Results. During 2009 to 2020, annual TB incidence (cases per 100 000 persons) among non-Hispanic AI/AN alone persons (range = 3.87-8.56) was on average 1.9 times higher than among all AI/AN persons (range = 1.89-4.70). Compared with non-Hispanic AI/AN alone patients with TB, multiracial/Hispanic AI/AN patients were significantly more likely to be HIV positive (prevalence ratio [PR] = 2.05) and to have been diagnosed while a resident of a correctional facility (PR = 1.71), and significantly less likely to have experienced homelessness (PR = 0.53) or died during TB treatment (PR = 0.47). Conclusions. Racial and ethnic disaggregation revealed significant differences in TB epidemiology among AI/AN analytic groups. Exclusion of multiracial/Hispanic AI/AN persons from AI/AN analytic groups can substantively affect estimates of racial and ethnic health disparities. (Am J Public Health. 2024;114(2):226-236. https://doi.org/10.2105/AJPH.2023.307498).

Delay analysis of pulmonary tuberculosis in the eastern coastal county of China from 2010 to 2021: evidence from two surveillance systems

Background

Tuberculosis (TB) remains a major public health challenge. However, indicators of delays in assessing effective TB prevention and control and its influencing factors have not been investigated in the eastern coastal county of China.

Methods

All notified pulmonary tuberculosis (PTB) cases in the Fenghua District, China were collected between 2010 and 2021 from the available TB information management system. Comparison of delays involving patient, health system, and total delays among local and migrant cases. Additionally, in correlation with available Basic Public Health Service Project system, we performed univariate and multivariate logistic regression analyses identified the influencing factors associated with patient and total delays in patients aged >60 years.

Results

In total, 3,442 PTB cases were notified, including 1,725 local and 1,717 migrant patients, with a male-to-female ratio of 2.13:1. Median patient and total delays of local TB patients were longer than those for migrant patients; the median health system delay did not show any significant difference. For patient delay among the older adult, female (cOR: 1.93, 95% CI: 1.07-3.48), educational level of elementary school and middle school (cOR: 0.23, 95% CI: 0.06-0.84) had a statistical difference from univariable analysis; however, patients without diabetes showed a higher delay for multiple-factor analysis (aOR: 2.12, 95% CI: 1.02-4.41). Furthermore, only the education level of elementary school and middle school presented a low total delay for both univariate (cOR: 0.22, 95% CI: 0.06-0.82) and multivariate analysis (aOR: 0.21, 95% CI: 0.05-0.83) in the older patients.

Conclusion

The delay of TB cases among migrants was lower than the local population in the Fenghua District, which may be related to the "healthy migrant effect". It highlights that women, illiterate people, and people without diabetes are key groups for reducing delays among older adults. Health awareness should focus on these target populations, providing accessible health services, and reducing the time from symptom onset to diagnosis.

Tuberculosis Diagnoses Following Wildfire Smoke Exposure in California

Rationale: Wildfires are a significant cause of exposure to ambient air pollution in the United States and other settings. Although indoor air pollution is a known contributor to tuberculosis reactivation and progression, it is unclear whether ambient pollution exposures, including wildfire smoke, similarly increase risk. Objectives: To determine whether tuberculosis diagnosis was associated with recent exposure to acute outdoor air pollution events, including those caused by wildfire smoke. Methods: We conducted a case-crossover analysis of 6,238 patients aged ⩾15 years diagnosed with active tuberculosis disease between 2014 and 2019 in 8 California counties. Using geocoded address data, we characterized individuals' daily exposure to <2.5 μm-diameter particulate matter (PM_2.5) during counterfactual risk periods 3-6 months before tuberculosis diagnosis (hazard period) and the same time 1 year previously (control period). We compared the frequency of residential PM_2.5 exposures exceeding 35 μg/m³ (PM_2.5 events) overall and for wildfire-associated and nonwildfire events during individuals' hazard and control periods. Measurements and Main Results: In total, 3,139 patients experienced 1 or more PM_2.5 events during the hazard period, including 671 experiencing 1 or more wildfire-associated events. Adjusted odds of tuberculosis diagnosis increased by 5% (95% confidence interval, 3-6%) with each PM_2.5 event experienced over the 6-month observation period. Each wildfire-associated PM_2.5 event was associated with 23% (19-28%) higher odds of tuberculosis diagnosis in this time window, whereas no association was apparent for nonwildfire-associated events. Conclusions: Residential exposure to wildfire-associated ambient air pollution is associated with an increased risk of active tuberculosis diagnosis.

Association of Area-Based Socioeconomic Measures with Tuberculosis Incidence in California

We assessed the association of area-based socio-economic status (SES) measures with tuberculosis (TB) incidence in California. We used TB disease data for 2012-2016 (n = 9901), population estimates, and SES measures to calculate incidence rates, rate ratios, and 95% confidence intervals (95% CI) by SES and birth country. SES was measured by census tract and was categorized by quartiles for education, crowding, and the California Healthy Places Index (HPI)and by specific cutoffs for poverty. The lowest SES areas defined by education, crowding, poverty, and HPI had 39%, 40%, 41%, and 33% of TB cases respectively. SES level was inversely associated with TB incidence across all SES measures and birth countries. TB rates were 3.2 (95% CI 3.0-3.4), 2.1 (95% CI 1.9-2.2), 3.6 (95% CI 3.3-3.8), and 2.0 (95% CI 1.9-2.1) times higher in lowest SES areas vs. highest SES areas as defined by education, crowding, poverty and HPI respectively. Area-based SES measures are associated with TB incidence in California. This information could inform TB prevention efforts in terms of materials, partnerships, and prioritization.

Challenges in treating tuberculosis in the elderly population in tertiary institute

Tuberculosis (TB) epidemic is most prevalent in the India with increase in mortality and morbidity. Ongoing elderly population as a result of increase in health care facilities are at high risk of TB. Elderly people are four-fold more prone to TB. Most cases of TB in the elderly result from reactivation of latent TB due to immunosenescence. Major challenge in dealing with therapeutic aspects of elderly patients is recognising frailty to prevent loss of independence. Challenges facing with elderly TB are difficult to reach out to hospital because of poor health seeking behaviour especially elderly female either due to ignorance or neglected by the family members, atypical presentation mimicking other disorders leading to diagnostic delay, if at all diagnosed impoverished tolerance and adherence to treatment due to various factors like associated comorbidities leading to pill load, impaired renal and hepatic functions with aging and stigma. Emerging resistance with usage of non-standard treatment regimens lead to unpropitious outcomes and increases mortality. The mortality rate is six times higher in elderly compared to younger individuals. Hence elderly people need tertiary level health care facilities for enhancing the diagnosis and appropriate management of tuberculosis and its complications. New set of guidelines to be made for elderly to increase adherence and tolerance thereby decreasing drug interactions and adverse drug reactions. With the increased prevalence of TB in the elderly, it is the need of the hour for India, to focus on this vulnerable population as they are a potential source of infection in the community. Awareness to be created among the elderly community regarding this deadly disease and its outcomes to increase their health consciousness and medical attention. Priming the special focus on females coterie as they are the most neglected population in our society.

Using Machine Learning Techniques and National Tuberculosis Surveillance Data to Predict Excess Growth in Genotyped Tuberculosis Clusters

The early identification of clusters of persons with tuberculosis (TB) that will grow to become outbreaks creates an opportunity for intervention in preventing future TB cases. We used surveillance data (2009-2018) from the United States, statistically derived definitions of unexpected growth, and machine-learning techniques to predict which clusters of genotype-matched TB cases are most likely to continue accumulating cases above expected growth within a 1-year follow-up period. We developed a model to predict which clusters are likely to grow on a training and testing data set that was generalizable to a validation data set. Our model showed that characteristics of clusters were more important than the social, demographic, and clinical characteristics of the patients in those clusters. For instance, the time between cases before unexpected growth was identified as the most important of our predictors. A faster accumulation of cases increased the probability of excess growth being predicted during the follow-up period. We have demonstrated that combining the characteristics of clusters and cases with machine learning can add to existing tools to help prioritize which clusters may benefit most from public health interventions. For example, consideration of an entire cluster, not only an individual patient, may assist in interrupting ongoing transmission.

Model-based Analysis of Tuberculosis Genotype Clusters in the United States Reveals High Degree of Heterogeneity in Transmission and State-level Differences Across California, Florida, New York, and Texas

BACKGROUND

Reductions in tuberculosis (TB) transmission have been instrumental in lowering TB incidence in the United States. Sustaining and augmenting these reductions are key public health priorities.

METHODS

We fit mechanistic transmission models to distributions of genotype clusters of TB cases reported to the Centers for Disease Control and Prevention during 2012-2016 in the United States and separately in California, Florida, New York, and Texas. We estimated the mean number of secondary cases generated per infectious case (R0) and individual-level heterogeneity in R0 at state and national levels and assessed how different definitions of clustering affected these estimates.

RESULTS

In clusters of genotypically linked TB cases that occurred within a state over a 5-year period (reference scenario), the estimated R0 was 0.29 (95% confidence interval [CI], .28-.31) in the United States. Transmission was highly heterogeneous; 0.24% of simulated cases with individual R0 >10 generated 19% of all recent secondary transmissions. R0 estimate was 0.16 (95% CI, .15-.17) when a cluster was defined as cases occurring within the same county over a 3-year period. Transmission varied across states: estimated R0s were 0.34 (95% CI, .3-.4) in California, 0.28 (95% CI, .24-.36) in Florida, 0.19 (95% CI, .15-.27) in New York, and 0.38 (95% CI, .33-.46) in Texas.

CONCLUSIONS

TB transmission in the United States is characterized by pronounced heterogeneity at the individual and state levels. Improving detection of transmission clusters through incorporation of whole-genome sequencing and identifying the drivers of this heterogeneity will be essential to reducing TB transmission.

Tuberculosis in Indigenous Persons - United States, 2009-2019

BACKGROUND

Populations of indigenous persons are frequently associated with pronounced disparities in rates of tuberculosis (TB) disease compared to co-occurring nonindigenous populations.

METHODS

Using data from the National Tuberculosis Surveillance System on TB cases in U.S.-born patients reported in the United States during 2009-2019, we calculated incidence rate ratios and risk ratios for TB risk factors to compare cases in American Indian or Alaska Native (AIAN) and Native Hawaiian or other Pacific Islander (NHPI) TB patients to cases in White TB patients.

RESULTS

Annual TB incidence rates among AIAN and NHPI TB patients were on average ≥10 times higher than among White TB patients. Compared to White TB patients, AIAN and NHPI TB patients were 1.91 (95% confidence interval (CI): 1.35-2.71) and 3.39 (CI: 1.44-5.74) times more likely to have renal disease or failure, 1.33 (CI: 1.16-1.53) and 1.63 (CI: 1.20-2.20) times more likely to have diabetes mellitus, and 0.66 (CI: 0.44-0.99) and 0.19 (CI: 0-0.59) times less likely to be HIV positive, respectively. AIAN TB patients were 1.84 (CI: 1.69-2.00) and 1.48 (CI: 1.27-1.71) times more likely to report using excess alcohol and experiencing homelessness, respectively.

CONCLUSION

TB among U.S. indigenous persons is associated with persistent and concerning health disparities.

A narrative review of tuberculosis in the United States among persons aged 65 years and older

Tuberculosis (TB) is a preventable infectious disease that confers significant morbidity, mortality, and psychosocial challenges. As TB incidence in the United States (U.S.) decreased from 9.7/100,000 to 2.2/100,000 from 1993 to 2020, the proportion of cases occurring among adults aged 65 and older increased. We conducted a review of published literature in the U.S. and other similar low-TB-burden settings to characterize the epidemiology and unique diagnostic challenges of TB in older adults. This narrative review also provides an overview of treatment characteristics, outcomes, and research gaps in this patient population. Older adults had a 30% higher likelihood of delayed TB diagnosis, with contributing factors such as acid-fast bacilli sputum smear-negative disease (56%) and non-classical clinical presentation. At least 90% of TB cases among older adults resulted from reactivation of latent TB infection (LTBI), but guidance around when to screen and treat LTBI in these patients is lacking. In addition, routine TB testing methods such as interferon-gamma release assays were two times more likely to have false-negative results among older adults. Advanced age was also often accompanied by complex comorbidities and impaired drug metabolism, increasing the risk of treatment failure (23%) and death (19%). A greater understanding of the unique factors of TB among older adults will inform clinical and public health efforts to improve outcomes in this complex patient population and TB control in the U.S.

Health insurance, healthcare utilization and language use among populations who experience risk for tuberculosis, California 2014–2017

Background

California tuberculosis (TB) prevention goals include testing more than ten million at-risk Californians and treating two million infected with tuberculosis. Adequate health insurance and robust healthcare utilization are crucial to meeting these goals, but information on these factors for populations that experience risk for TB is limited.

Methods

We used data from the 2014–2017 California Health Interview Survey (n = 82,758), a population-based dual-frame telephone survey to calculate survey proportions and 95% confidence intervals (CI) stratified by country of birth, focusing on persons from countries of birth with the highest number of TB cases in California. Survey proportions for recent doctor’s visit, overall health, smoking, and diabetes were age-adjusted.

Results

Among 18–64 year-olds, 27% (CI: 25–30) of persons born in Mexico reported being uninsured in contrast with 3% (CI: 1–5) of persons born in India. Report of recent doctor’s visit was highest among persons born in the Philippines, 84% (CI: 80–89) and lowest among Chinese-born persons, 70% (CI: 63–76). Persons born in Mexico were more likely to report community clinics as their usual source of care than persons born in China, Vietnam, or the Philippines. Poverty was highest among Mexican-born persons, 56% (CI: 54–58) and lowest among Indian-born persons, 9% (CI: 5–13). Of adults with a medical visit in a non-English language, 96% (CI: 96–97) were non-U.S.-born, but only 42% (CI: 40–44) of non-U.S.-born persons had a visit in a non-English language.

Discussion

Many, though not all, of the populations that experience risk for TB had health insurance and used healthcare. We found key differences in usual source of care and language use by country of birth which should be considered when planning outreach to specific providers, clinic systems, insurers and communities for TB prevention and case-finding.

The Health and Economic Benefits of Tests That Predict Future Progression to Tuberculosis Disease

BACKGROUND

Effective targeting of latent tuberculosis infection (LTBI) treatment requires identifying those most likely to progress to tuberculosis (TB). We estimated the potential health and economic benefits of diagnostics with improved discrimination for LTBI that will progress to TB.

METHODS

A base case scenario represented current LTBI testing and treatment services in the United States in 2020, with diagnosis via. interferon-gamma release assay (IGRA). Alternative scenarios represented tests with higher positive predictive value (PPV) for future TB but similar price to IGRA, and scenarios that additionally assumed higher treatment initiation and completion. We predicted outcomes using multiple transmission-dynamic models calibrated to different geographic areas and estimated costs from a societal perspective.

RESULTS

In 2020, 2.1% (range across model results: 1.1%-3.4%) of individuals with LTBI were predicted to develop TB in their remaining lifetime. For IGRA, we estimated the PPV for future TB as 1.3% (0.6%-1.8%). Relative to IGRA, we estimated a test with 10% PPV would reduce treatment volume by 87% (82%-94%), reduce incremental costs by 30% (15%-52%), and increase quality-adjusted life years by 3% (2%-6%). Cost reductions and health improvements were substantially larger for scenarios in which higher PPV for future TB was associated with greater initiation and completion of treatment.

CONCLUSIONS

We estimated that tests with better predictive performance would substantially reduce the number of individuals treated to prevent TB but would have a modest impact on incremental costs and health impact of TB prevention services, unless accompanied by greater treatment acceptance and completion.

How much do smear-negative patients really contribute to tuberculosis transmissions? Re-examining an old question with new tools

BACKGROUND

Sputum smear microscopy is a common surrogate for tuberculosis infectiousness. Previous estimates that smear-negative patients contribute 13-20% of transmissions and are, on average, 20 to 25% as infectious as smear-positive cases are understood to be high. Herein, we use an ideal real-world setting, a comprehensive dataset, and new high-resolution techniques to more accurately estimate the true transmission risk of smear-negative cases.

METHODS

We treated all adult culture-positive pulmonary TB patients diagnosed in the province of Alberta, Canada from 2003 to 2016 as potential transmitters. The primary data sources were the Alberta TB Registry and the Provincial Laboratory for Public Health. We measured, as primary outcomes, the proportion of transmissions attributable to smear-negative sources and the relative transmission rate. First, we replicated previous studies by using molecular (DNA) fingerprint clustering. Then, using a prospectively collected registry of TB contacts, we defined transmission events as active TB amongst identified contacts who either had a 100% DNA fingerprint match to the source case or a clinical diagnosis. We supplemented our analysis with genome sequencing on temporally and geographically linked DNA fingerprint clusters of cases not identified as contacts.

FINDINGS

There were 1176 cases, 563 smear-negative and 613 smear-positive, and 23,131 contacts. Replicating previous studies, the proportion of transmissions attributable to smear-negative source cases was 16% (95% CI, 12-19%) and the relative transmission rate was 0.19 (95% CI, 0.14-0.26). With our combined approach, the proportion of transmission was 8% (95% CI, 3-14%) and the relative transmission rate became 0.10 (95% CI, 0.05-0.19).

INTERPRETATION

When we examined the same outcomes as in previous studies but refined transmission ascertainment with the addition of conventional epidemiology and genomics, we found that smear-negative cases were ∼50% less infectious than previously thought.

FUNDING

Alberta Innovates Health Solutions.

Trends, mechanisms, and racial/ethnic differences of tuberculosis incidence in the US-born population aged 50 years or older in the United States

Background

Older age is a risk factor for tuberculosis (TB) in low incidence settings. Using data from the US National TB Surveillance System and American Community Survey, we estimated trends and racial/ethnic differences in TB incidence among US-born cohorts aged ≥50 years.

Methods

In total, 42 000 TB cases among US-born persons ≥50 years were reported during 2001–2019. We used generalized additive regression models to decompose the effects of birth cohort and age on TB incidence rates, stratified by sex and race/ethnicity. Using genotype-based estimates of recent transmission (available 2011–2019), we implemented additional models to decompose incidence trends by estimated recent versus remote infection.

Results

Estimated incidence rates declined with age, for the overall cohort and most sex and race/ethnicity strata. Average annual percentage declines flattened for older individuals, from 8.80% (95% confidence interval [CI] 8.34–9.23) in 51-year-olds to 4.51% (95% CI 3.87–5.14) in 90-year-olds. Controlling for age, incidence rates were lower for more recent birth cohorts, dropping 8.79% (95% CI 6.13–11.26) on average between successive cohort years. Incidence rates were substantially higher for racial/ethnic minorities, and these inequalities persisted across all birth cohorts. Rates from recent infection declined at approximately 10% per year as individuals aged. Rates from remote infection declined more slowly with age, and this annual percentage decline approached zero for the oldest individuals.

Conclusions

TB rates were highest for racial/ethnic minorities and for the earliest birth cohorts and declined with age. For the oldest individuals, annual percentage declines were low, and most cases were attributed to remote infection.

Association between Birth Region and Time to Tuberculosis Diagnosis among Non-US-Born Persons in the United States

Approximately 90% of tuberculosis (TB) cases among non–US-born persons in the United States are attributable to progression of latent TB infection to TB disease. Using survival analysis, we investigated whether birthplace is associated with time to disease progression among non–US-born persons in whom TB disease developed. We derived a Cox regression model comparing differences in time to TB diagnosis after US entry among 19 birth regions, adjusting for sex, birth year, and age at entry. After adjusting for age at entry and birth year, the median time to TB diagnosis was lowest among persons from Middle Africa, 128 months (95% CI 116–146 months) for male persons and 121 months (95% CI 108–136 months) for female persons. We found time to TB diagnosis among non–US-born persons varied by birth region, which represents a prognostic indicator for progression of latent TB infection to TB disease.

Multidrug-resistant tuberculosis in the United States, 2011-2016: patient characteristics and risk factors

OBJECTIVE: To determine risk factors for multidrug-resistant tuberculosis (MDR-TB) and describe MDR-TB according to three characteristics: previous TB disease, recent transmission of MDR-TB, and reactivation of latent MDR-TB infection.SETTING and DESIGN: We used 2011-2016 surveillance data from the US National Tuberculosis Surveillance System and National Tuberculosis Genotyping Service and used logistic regression models to estimate risk factors associated with MDR-TB.RESULTS: A total of 615/45 209 (1.4%) cases were confirmed as MDR-TB; 111/615 (18%) reported previous TB disease; 41/615 (6.7%) were attributed to recent MDR-TB transmission; and 449/615 (73%) to reactivation. Only 12/41 (29%) patients with TB attributed to recent transmission were known to be contacts of someone with MDR-TB. For non-US-born patients, the adjusted odds ratios of having MDR-TB were 32.6 (95%CI 14.6-72.6) among those who were known to be contacts of someone with MDR-TB and 6.5 (95%CI 5.1-8.3) among those who had had previous TB disease.CONCLUSION: The majority of MDR-TB cases in the United States were associated with previous TB disease or reactivation of latent MDR-TB infection; only a small proportion of MDR-TB cases were associated with recent transmission.

Quantifying geographic heterogeneity in TB incidence and the potential impact of geographically targeted interventions in South and North City Corporations of Dhaka, Bangladesh: a model-based study

In rapidly growing and high-burden urban centres, identifying tuberculosis (TB) transmission hotspots and understanding the potential impact of interventions can inform future control and prevention strategies. Using data on local demography, TB reports and patient reporting patterns in Dhaka South City Corporation (DSCC) and Dhaka North City Corporation (DNCC), Bangladesh, between 2010 and 2017, we developed maps of TB reporting rates across wards in DSCC and DNCC and identified wards with high rates of reported TB (i.e. 'hotspots') in DSCC and DNCC. We developed ward-level transmission models and estimated the potential epidemiological impact of three TB interventions: active case finding (ACF), mass preventive therapy (PT) and a combination of ACF and PT, implemented either citywide or targeted to high-incidence hotspots. There was substantial geographic heterogeneity in the estimated TB incidence in both DSCC and DNCC: incidence in the highest-incidence wards was over ten times higher than in the lowest-incidence wards in each city corporation. ACF, PT and combined ACF plus PT delivered to 10% of the population reduced TB incidence by a projected 7%-9%, 13%-15% and 19%-23% over five years, respectively. Targeting TB hotspots increased the projected reduction in TB incidence achieved by each intervention 1.4- to 1.8-fold. The geographical pattern of TB notifications suggests high levels of ongoing TB transmission in DSCC and DNCC, with substantial heterogeneity at the ward level. Interventions that reduce transmission are likely to be highly effective and incorporating notification data at the local level can further improve intervention efficiency.

State-level prevalence estimates of latent tuberculosis infection in the United States by medical risk factors, demographic characteristics and nativity

INTRODUCTION

Preventing tuberculosis (TB) disease requires treatment of latent TB infection (LTBI) as well as prevention of person-to-person transmission. We estimated the LTBI prevalence for the entire United States and for each state by medical risk factors, age, and race/ethnicity, both in the total population and stratified by nativity.

METHODS

We created a mathematical model using all incident TB disease cases during 2013-2017 reported to the National Tuberculosis Surveillance System that were classified using genotype-based methods or imputation as not attributed to recent TB transmission. Using the annual average number of TB cases among US-born and non-US-born persons by medical risk factor, age group, and race/ethnicity, we applied population-specific reactivation rates (and corresponding 95% confidence intervals [CI]) to back-calculate the estimated prevalence of untreated LTBI in each population for the United States and for each of the 50 states and the District of Columbia in 2015.

RESULTS

We estimated that 2.7% (CI: 2.6%-2.8%) of the U.S. population, or 8.6 (CI: 8.3-8.8) million people, were living with LTBI in 2015. Estimated LTBI prevalence among US-born persons was 1.0% (CI: 1.0%-1.1%) and among non-US-born persons was 13.9% (CI: 13.5%-14.3%). Among US-born persons, the highest LTBI prevalence was in persons aged ≥65 years (2.1%) and in persons of non-Hispanic Black race/ethnicity (3.1%). Among non-US-born persons, the highest LTBI prevalence was estimated in persons aged 45-64 years (16.3%) and persons of Asian and other racial/ethnic groups (19.1%).

CONCLUSIONS

Our estimations of the prevalence of LTBI by medical risk factors and demographic characteristics for each state could facilitate planning for testing and treatment interventions to eliminate TB in the United States. Our back-calculation method feasibly estimates untreated LTBI prevalence and can be updated using future TB disease case counts at the state or national level.

Estimating and Evaluating Tuberculosis Incidence Rates Among People Experiencing Homelessness, United States, 2007-2016

OBJECTIVES

Persons experiencing homelessness (PEH) are disproportionately affected by tuberculosis (TB). We estimate area-specific rates of TB among PEH and characterize the extent to which available data support recent transmission as an explanation of high TB incidence.

METHODS

We estimated TB incidence among PEH using National Tuberculosis Surveillance System data and population estimates for the US Department of Housing and Urban Development's Continuums of Care areas. For areas with TB incidence higher than the national average among PEH, we estimated recent transmission using genotyping and a plausible source-case method. For cases with ≥1 plausible source case, we assessed with TB program partners whether available whole-genome sequencing and local epidemiologic data were consistent with recent transmission.

RESULTS

During 2011-2016, 3164 TB patients reported experiencing homelessness. National incidence was 36 cases/100,000 PEH. Incidence estimates varied among 21 areas with ≥10,000 PEH (9-150 cases/100,000 PEH); 9 areas had higher than average incidence. Of the 2349 cases with Mycobacterium tuberculosis genotyping results, 874 (37%) had ≥1 plausible source identified. In the 9 areas, 23%-82% of cases had ≥1 plausible source. Of cases with ≥1 plausible source, 63% were consistent and 7% were inconsistent with recent transmission; 29% were inconclusive.

CONCLUSIONS

Disparities in TB incidence for PEH persist; estimates of TB incidence and recent transmission vary by area. With a better understanding of the TB risk among PEH in their jurisdictions and the role of recent transmission as a driver, programs can make more informed decisions about prioritizing TB prevention strategies.

Estimating the relative probability of direct transmission between infectious disease patients

BACKGROUND

Estimating infectious disease parameters such as the serial interval (time between symptom onset in primary and secondary cases) and reproductive number (average number of secondary cases produced by a primary case) are important in understanding infectious disease dynamics. Many estimation methods require linking cases by direct transmission, a difficult task for most diseases.

METHODS

Using a subset of cases with detailed genetic and/or contact investigation data to develop a training set of probable transmission events, we build a model to estimate the relative transmission probability for all case-pairs from demographic, spatial and clinical data. Our method is based on naive Bayes, a machine learning classification algorithm which uses the observed frequencies in the training dataset to estimate the probability that a pair is linked given a set of covariates.

RESULTS

In simulations, we find that the probabilities estimated using genetic distance between cases to define training transmission events are able to distinguish between truly linked and unlinked pairs with high accuracy (area under the receiver operating curve value of 95%). Additionally, only a subset of the cases, 10-50% depending on sample size, need to have detailed genetic data for our method to perform well. We show how these probabilities can be used to estimate the average effective reproductive number and apply our method to a tuberculosis outbreak in Hamburg, Germany.

CONCLUSIONS

Our method is a novel way to infer transmission dynamics in any dataset when only a subset of cases has rich contact investigation and/or genetic data.

Time Since Infection and Risks of Future Disease for Individuals with Mycobacterium tuberculosis Infection in the United States

BACKGROUND

Risk of tuberculosis (TB) declines over time since Mycobacterium tuberculosis infection, but progression to clinical disease is still possible decades later. In the United States, most TB cases result from the progression of latent TB infection acquired over 2 years ago.

METHODS

We synthesized evidence on TB natural history and incidence trends using a transmission-dynamic model. For the 2020 US population, we estimated average time since infection and annual, cumulative, and remaining lifetime risks of progression to TB, by nativity and age.

RESULTS

For a newly infected adult with no other risk factors for progression to TB, estimated rates of progression declined from 38 (95% uncertainty interval: 33, 46) to 0.38 (0.32, 0.45) per 1000 person-years between the first and 25th year since infection. Cumulative risk over 25 years from new infection was 7.9% (7.0, 8.9). In 2020, an estimated average age of individuals with prevalent infection was 62 (61, 63) for the US-born population, 55 (54, 55) for non-US-born, and 57 (56, 58) overall. Average risks of developing TB over the remaining lifetime were 1.2% (1.0, 1.4) for US-born, 2.2% (1.8, 2.6) for non-US-born, and 1.9% (1.6, 2.2) for the general population. Risk estimates were higher for younger age groups.

CONCLUSIONS

Our analysis suggests that, although newly infected individuals face appreciable lifetime TB risks, most US individuals with latent TB infection were infected long ago, and face low future risks of developing TB. Better approaches are needed for identifying recently infected individuals and those with elevated progression risks.

Impact of Effective Global Tuberculosis Control on Health and Economic Outcomes in the United States

Rationale: Most U.S. residents who develop tuberculosis (TB) were born abroad, and U.S. TB incidence is increasingly driven by infection risks in other countries.

Objectives: To estimate the potential impact of effective global TB control on health and economic outcomes in the United States.

Methods: We estimated outcomes using linked mathematical models of TB epidemiology in the United States and migrants’ birth countries. A base-case scenario extrapolated country-specific TB incidence trends. We compared this with scenarios in which countries achieve 90% TB incidence reductions between 2015 and 2035, as targeted by the World Health Organization’s End TB Strategy (“effective global TB control”). We also considered pessimistic scenarios of flat TB incidence trends in individual countries.

Measurements and Main Results: We estimated TB cases, deaths, and costs and the total economic burden of TB in the United States. Compared with the base-case scenario, effective global TB control would avert 40,000 (95% uncertainty interval, 29,000–55,000) TB cases in the United States in 2020–2035. TB incidence rates in 2035 would be 43% (95% uncertainty interval, 34–54%) lower than in the base-case scenario, and 49% (95% uncertainty interval, 44–55%) lower than in 2020. Summed over 2020–2035, this represents 0.8 billion dollars (95% uncertainty interval, 0.6–1.0 billion dollars) in averted healthcare costs and $2.5 billion dollars (95% uncertainty interval, 1.7–3.6 billion dollars) in productivity gains. The total U.S. economic burden of TB (including the value of averted TB deaths) would be 21% (95% uncertainty interval, 16–28%) lower (18 billion dollars [95% uncertainty level, 8–32 billion dollars]).

Conclusions: In addition to producing major health benefits for high-burden countries, strengthened efforts to achieve effective global TB control could produce substantial health and economic benefits for the United States.

Tuberculosis Transmission or Mortality Among Persons Living with HIV, USA, 2011-2016

BACKGROUND

Persons living with HIV are more likely to have tuberculosis (TB) disease attributed to recent transmission (RT) and to die during TB treatment than persons without HIV. We examined factors associated with RT or mortality among TB/HIV patients.

METHODS

Using National TB Surveillance System data from 2011 to 2016, we calculated multivariable adjusted odds ratios (aOR) with 99% confidence intervals (CI) to estimate associations between patient characteristics and RT or mortality. Mortality analyses were restricted to 2011-2014 to allow sufficient time for reporting outcomes.

RESULTS

TB disease was attributed to RT in 491 (20%) of 2415 TB/HIV patients. RT was more likely among those reporting homelessness (aOR, 2.6; CI, 2.0, 3.5) or substance use (aOR,1.6; CI, 1.2, 2.1) and among blacks (aOR,1.8; CI, 1.2, 2.8) and Hispanics (aOR, 1.8; CI, 1.1, 2.9); RT was less likely among non-US-born persons (aOR, 0.2; CI, 0.2, 0.3). The proportion who died during TB treatment was higher among persons with HIV than without (8.6% versus 5.2%; p < 0.0001). Among 2273 TB/HIV patients, 195 died during TB treatment. Age ≥ 65 years (aOR, 5.3; CI, 2.4, 11.6), 45-64 years (aOR, 2.2; CI, 1.4, 3.4), and having another medical risk factor for TB (aOR, 3.3; CI, 1.8, 6.2) were associated with death; directly observed treatment (DOT) for TB was protective (aOR, 0.5; CI, 0.2, 1.0).

CONCLUSIONS

Among TB/HIV patients, blacks, Hispanics, and those reporting homelessness or substance use should be prioritized for interventions that decrease TB transmission. Improved adherence to treatment through DOT was associated with decreased mortality, but additional interventions are needed to reduce mortality among older patients and those TB/HIV patients with another medical risk factor for TB.

Spatial distribution of tuberculosis incidence in Los Angeles County

Background

In Los Angeles County, the tuberculosis (TB) disease incidence rate is seven times higher among non-U.S.-born persons than U.S.-born persons and varies by country of birth. But translating these findings into public health action requires more granular information, especially considering that Los Angeles County is more than 4000 mile². Local public health authorities may benefit from data on which areas of the county are most affected, yet these data remain largely unreported in part because of limitations of sparse data. We aimed to describe the spatial distribution of TB disease incidence in Los Angeles County while addressing challenges arising from sparse data and accounting for known cofactors.

Methods

Data on 5447 TB cases from Los Angeles County were combined with stratified population estimates available from the 2005–2011 Public Use Microdata Survey. TB disease incidence rates stratified by country of birth and Public Use Microdata Area were calculated and spatial smoothing was applied using a conditional autoregressive model. We used Bayesian Poisson models to investigate spatial patterns adjusting for age, sex, country of birth and years since initial arrival in the U.S.

Results

There were notable differences in the crude and spatially-smoothed maps of TB disease rates for high-risk subgroups, namely persons born in Mexico, Vietnam or the Philippines. Spatially-smoothed maps showed areas of high incidence in downtown Los Angeles and surrounding areas for persons born in the Philippines or Vietnam. Areas of high incidence were more dispersed for persons born in Mexico. Adjusted models suggested that the spatial distribution of TB disease could not be fully explained using age, sex, country of birth and years since initial arrival.

Conclusions

This study highlights areas of high TB incidence within Los Angeles County both for U.S.-born cases and for cases born in Mexico, Vietnam or the Philippines. It also highlights areas that had high incidence rates even when accounting for non-spatial error and country of birth, age, sex, and years since initial arrival in the U.S. Information on spatial distribution provided here complements other descriptions of local disease burden and may help focus ongoing efforts to scale up testing for TB infection and treatment among high-risk subgroups.

Estimated Latent Tuberculosis Infection Prevalence and Tuberculosis Reactivation Rates Among Non-U.S.-Born Residents in the United States, from the 2011-2012 National Health and Nutrition Examination Survey

Increased testing and treatment of latent tuberculosis infection (LTBI) among US-residents who were born (or lived) in countries with high rates of TB can hasten progress toward TB elimination. We calculated LTBI prevalence using QuantiFERON®-TB Gold In-Tube results from the 2011 to 2012 National Health and Nutrition Examination Survey (NHANES). LTBI prevalence was highest for persons born in India (31.7%, 95% confidence interval [21.2, 44.5]). Non-Hispanic white persons had the lowest LTBI prevalence (6.3% [1.9, 18.9]). TB reactivation rate, defined as the number of TB cases not associated with recent transmission per 100 person-years of life with LTBI, was highest for persons born in Vietnam [0.183 (0.117, 0.303)]. Reactivation rates were lower among persons who had resided in the United States for ≥ 10 years than among those who had resided for < 10 years. Results among high risk populations can guide LTBI targeted testing and treatment among non-U.S.-born residents.

Screening migrants from tuberculosis high-endemic countries for latent tuberculosis in Oman: A cross sectional cohort analysis

To fulfil the World Health Organization (WHO) End TB strategy, screening for tuberculosis (TB) in immigrants is an important component of the strategy to reduce the TB burden in low-incidence countries. Oman has an annual TB incidence rate of 5.7 per 100000 and transmission from migrants with activated latent TB infection (LTBI) to nationals is a concern. The aim of this study was to determine the proportion of migrants to the Sultanate of Oman with LTBI. The study used an interferon-gamma release assay (IGRA) to assess previous exposure to TB, defining LTBI and a positive IGRA with a normal chest X-ray. 1049 subjects were surveyed. Six participants were excluded from the analysis as they had been recently vaccinated and 1 had an indeterminate result, thus 1042 subjects were included. The overall IGRA-positive rate was 22.4% (234/1042), 30.9% and 21.2% of African and Asian migrants, respectively, were IGRA-positive. Fifty-eight of the participants had a strong IGRA reactivity defined as more than 4 IU/ml. The study shows the proportion of migrants from Asia and Africa with LTBI and 24.7% (58/234) of IGRA-positive migrants had an IGRA of >4 IU/ml, defining a subpopulation with a high risk of developing active TB in the first two years of arrival to the country.

Comparative Modeling of Tuberculosis Epidemiology and Policy Outcomes in California

Rationale: Mathematical modeling is used to understand disease dynamics, forecast trends, and inform public health prioritization. We conducted a comparative analysis of tuberculosis (TB) epidemiology and potential intervention effects in California, using three previously developed epidemiologic models of TB.Objectives: To compare the influence of various modeling methods and assumptions on epidemiologic projections of domestic latent TB infection (LTBI) control interventions in California.Methods: We compared model results between 2005 and 2050 under a base-case scenario representing current TB services and alternative scenarios including: 1) sustained interruption of Mycobacterium tuberculosis (Mtb) transmission, 2) sustained resolution of LTBI and TB prior to entry of new residents, and 3) one-time targeted testing and treatment of LTBI among 25% of non-U.S.-born individuals residing in California.Measurements and Main Results: Model estimates of TB cases and deaths in California were in close agreement over the historical period but diverged for LTBI prevalence and new Mtb infections-outcomes for which definitive data are unavailable. Between 2018 and 2050, models projected average annual declines of 0.58-1.42% in TB cases, without additional interventions. A one-time LTBI testing and treatment intervention among non-U.S.-born residents was projected to produce sustained reductions in TB incidence. Models found prevalent Mtb infection and migration to be more significant drivers of future TB incidence than local transmission.Conclusions: All models projected a stagnation in the decline of TB incidence, highlighting the need for additional interventions including greater access to LTBI diagnosis and treatment for non-U.S.-born individuals. Differences in model results reflect gaps in historical data and uncertainty in the trends of key parameters, demonstrating the need for high-quality, up-to-date data on TB determinants and outcomes.

Changes in tuberculosis epidemiology, United States, 1993-2017

BACKGROUND: After 20 years of steady decline, the pace of decline of tuberculosis (TB) incidence in the United States has slowed.METHODS: Trends in TB incidence rates and case counts since 1993 were assessed using national US surveillance data. Patient characteristics reported during 2014-2017 were compared with those for 2010-2013.RESULTS: TB rates and case counts slowed to an annual decline of respectively 2.2% (95%CI -3.4 to -1.0) and 1.5% (95%CI -2.7 to -0.3) since 2012, with decreases among US-born persons and no change among non-US-born persons. Overall, persons with TB diagnosed during 2014-2017 were older, more likely to have combined pulmonary and extra-pulmonary disease than extra-pulmonary disease alone, more likely to be of non-White race, and less likely to have human immunodeficiency virus infection, or cavitary pulmonary disease. During 2014-2017, non-US-born persons with TB were more likely to have diabetes mellitus, while the US-born were more likely to have smear-positive TB and use non-injecting drugs.CONCLUSION: Changes in epidemiologic trends are likely to affect TB incidence in the coming decades. The Centers for Disease Control and Prevention has called for increased attention to TB prevention through the detection and treatment of latent tuberculous infection.

Comparison of routine field epidemiology and whole genome sequencing to identify tuberculosis transmission in a remote setting

Yukon Territory (YT) is a remote region in northern Canada with ongoing spread of tuberculosis (TB). To explore the utility of whole genome sequencing (WGS) for TB surveillance and monitoring in a setting with detailed contact tracing and interview data, we used a mixed-methods approach. Our analysis included all culture-confirmed cases in YT (2005-2014) and incorporated data from 24-locus Mycobacterial Interspersed Repetitive Units-Variable Number of Tandem Repeats (MIRU-VNTR) genotyping, WGS and contact tracing. We compared field-based (contact investigation (CI) data + MIRU-VNTR) and genomic-based (WGS + MIRU-VNTR + basic case data) investigations to identify the most likely source of each person's TB and assessed the knowledge, attitudes and practices of programme personnel around genotyping and genomics using online, multiple-choice surveys (n = 4) and an in-person group interview (n = 5). Field- and genomics-based approaches agreed for 26 of 32 (81%) cases on likely location of TB acquisition. There was less agreement in the identification of specific source cases (13/22 or 59% of cases). Single-locus MIRU-VNTR variants and limited genetic diversity complicated the analysis. Qualitative data indicated that participants viewed genomic epidemiology as a useful tool to streamline investigations, particularly in differentiating latent TB reactivation from the recent transmission. Based on this, genomic data could be used to enhance CIs, focus resources, target interventions and aid in TB programme evaluation.

Interferon-γ Release Assays in Children <15 Years of Age

OBJECTIVES

The tuberculin skin test (TST) has been preferred for screening young children for latent tuberculosis infection (LTBI) because of concerns that interferon-γ release assays (IGRAs) may be less sensitive in this high-risk population. In this study, we compared the predictive value of IGRAs to the TST for progression to tuberculosis disease in children, including those <5 years old.

METHODS

Children <15 years old at risk for LTBI or progression to disease were tested with TST, QuantiFERON-TB Gold In-Tube test (QFT-GIT), and T-SPOT.TB test (T-SPOT) and followed actively for 2 years, then with registry matches, to identify incident disease.

RESULTS

Of 3593 children enrolled September 2012 to April 2016, 92% were born outside the United States; 25% were <5 years old. Four children developed tuberculosis over a median 4.3 years of follow-up. Sensitivities for progression to disease for TST and IGRAs were low (50%-75%), with wide confidence intervals (CIs). Specificities for TST, QFT-GIT, and T-SPOT were 73.4% (95% CI: 71.9-74.8), 90.1% (95% CI: 89.1-91.1), and 92.9% (95% CI: 92.0-93.7), respectively. Positive and negative predictive values for TST, QFT-GIT, and T-SPOT were 0.2 (95% CI: 0.1-0.8), 0.9 (95% CI: 0.3-2.5), and 0.8 (95% CI: 0.2-2.9) and 99.9 (95% CI: 99.7-100), 100 (95% CI: 99.8-100), and 99.9 (95% CI: 99.8-100), respectively. Of 533 children with TST-positive, IGRA-negative results not treated for LTBI, including 54 children <2 years old, none developed disease.

CONCLUSIONS

Although both types of tests poorly predict disease progression, IGRAs are no less predictive than the TST and offer high specificity and negative predictive values. Results from this study support the use of IGRAs for children, especially those who are not born in the United States.

Epidemiology of Tuberculosis in the United States

Although considerable progress has been made in reducing US tuberculosis incidence, the goal of eliminating the disease from the United States remains elusive. A continued focus on preventing new tuberculosis infections while also identifying and treating persons with existing tuberculosis infection is needed. Continued vigilance to ensure ongoing control of tuberculosis transmission remains key.

Contextualizing tuberculosis risk in time and space: comparing time-restricted genotypic case clusters and geospatial clusters to evaluate the relative contribution of recent transmission to incidence of TB using nine years of case data from Michigan, USA

PURPOSE

Novel approaches must address the underlying factors sustaining the tuberculosis (TB) epidemic in the United States, specifically what maintains new Mycobacterium tuberculosis (Mtb) transmission.

METHODS

Culture-confirmed TB cases reported to the Michigan Department of Health and Human Services (2004-2012) were analyzed for time-restricted genotypic and/or geospatial clustering. Cases with both types of clustering were used as a proxy for recent, local transmission. Modified, multivariate Poisson regression models were fit to estimate this prevalence in relation to various individual- and neighborhood-level demographic and socio-economic variables.

RESULTS

Those individuals that were spatially clustered were 1.7 times as likely to also be time-restricted genotypically clustered. The prevalence of recent, local transmission was higher among U.S.-born cases, males, and non-Hispanic blacks. Moreover, people living in neighborhoods in the highest poverty quartile had 13.8 times the prevalence of recent, local transmission compared with those in the lowest poverty neighborhoods.

CONCLUSIONS

Our results suggest geographic areas with high concentration of TB cases are likely driven by ongoing transmission, rather than enclaves of individuals who have reactivated a case of latent TB. Furthermore, efforts to continue reducing Mtb transmission in the United States, and other low-incidence settings, must better identify community-level sources of risk, manifested through the complex social interactions among people and their environments.

Ambulatory independence is associated with higher incidence of latent tuberculosis infection in long-term care facilities in Taiwan

BACKGROUND/PURPOSE

Tuberculosis (TB) in the elderly population remains a major challenge in areas with intermediate disease burden like Taiwan. Despite the increasing burden and high risks of TB in the elderly population, particularly those living in long-term care facilities (LTCFs), diagnostic testing for latent tuberculosis infection (LTBI) has not been carefully evaluated in this group. This study aimed to investigate the prevalence and predictors of LTBI in older adults living in LTCFs.

METHODS

Older adults living in seven LTCFs in Taiwan were prospectively enrolled between January and July 2017. Interferon-gamma release assay (IGRA) through QuantiFERON-TB Gold In-tube was used to determine presence of LTBI. Predictors for LTBI were analyzed.

RESULTS

A total of 258 participants were enrolled, including 240 older residents (mean age, 81.6 years; male, 51.2%) and 18 employees (mean age, 64.8 years; male, 22.2%). The proportion of independent status in ambulation assessments significantly declined with aging (p < 0.001). The IGRA-positivity rate in LTCFs was 31.4% (81/258), which consisted of 73 (30.4%) residents and 8 (44.4%) employees. The IGRA results were different with respect to the ambulation status (p = 0.052). In the multivariate logistic regression analysis, the only independent predictor of LTBI among older adults in LTCFs was independent ambulation (odds ratio, 2.16; 95% confidence interval, 1.09-4.28; p = 0.027).

CONCLUSIONS

There was a high prevalence of LTBI among older adults in LTCFs in Taiwan. Independent ambulation was the only independent predictor of LTBI.

The impact of migration on tuberculosis in the United States

Due to greater exposure to Mycobacterium tuberculosis infection before migration, migrants moving to low-incidence settings can experience substantially higher tuberculosis (TB) rates than the native-born population. This review describes the impact of migration on TB epidemiology in the United States, and how the TB burden differs between US-born and non-US-born populations. The United States has a long history of receiving migrants from other parts of the world, and TB among non-US-born individuals now represents the majority of new TB cases. Based on an analysis of TB cases among individuals from the top 30 countries of origin in terms of non-US-born TB burden between 2003 and 2015, we describe how TB risks vary within the non-US-born population according to age, years since entry, entry year, and country of origin. Variation along each of these dimensions is associated with more than 10-fold differences in the risk of developing active TB, and this risk is also positively associated with TB incidence estimates for the country of origin and the composition of the migrant pool in the entry year. Approximately 87 000 lifetime TB cases are predicted for the non-US-born population resident in the United States in 2015, and 5800 lifetime cases for the population entering the United States in 2015.

Impact and Effectiveness of State-Level Tuberculosis Interventions in California, Florida, New York, and Texas: A Model-Based Analysis

The incidence of tuberculosis (TB) in the United States has stabilized, and additional interventions are needed to make progress toward TB elimination. However, the impact of such interventions depends on local demography and the heterogeneity of populations at risk. Using state-level individual-based TB transmission models calibrated to California, Florida, New York, and Texas, we modeled 2 TB interventions: 1) increased targeted testing and treatment (TTT) of high-risk populations, including people who are non-US-born, diabetic, human immunodeficiency virus (HIV)-positive, homeless, or incarcerated; and 2) enhanced contact investigation (ECI) for contacts of TB patients, including higher completion of preventive therapy. For each intervention, we projected reductions in active TB incidence over 10 years (2016-2026) and numbers needed to screen and treat in order to avert 1 case. We estimated that TTT delivered to half of the non-US-born adult population could lower TB incidence by 19.8%-26.7% over a 10-year period. TTT delivered to smaller populations with higher TB risk (e.g., HIV-positive persons, homeless persons) and ECI were generally more efficient but had less overall impact on incidence. TTT targeted to smaller, highest-risk populations and ECI can be highly efficient; however, major reductions in incidence will only be achieved by also targeting larger, moderate-risk populations. Ultimately, to eliminate TB in the United States, a combination of these approaches will be necessary.

Simple Estimates for Local Prevalence of Latent Tuberculosis Infection, United States, 2011-2015

We used tuberculosis genotyping results to derive estimates of prevalence of latent tuberculosis infection in the United States. We estimated <1% prevalence in 1,981 US counties, 1%–<3% in 785 counties, and >3% in 377 counties. This method for estimating prevalence could be applied in any jurisdiction with an established tuberculosis surveillance system.

The problem with defining foreign birth as a risk factor in tuberculosis epidemiology studies

OBJECTIVE

To examine how stratifying persons born outside Canada according to tuberculosis (TB) incidence in their birth country and other demographic factors refines our understanding of TB epidemiology and local TB transmission.

BACKGROUND

Population-level TB surveillance programs and research studies in low incidence settings often report all persons born outside the country in which the study is conducted as "foreign-born"-a single label for a highly diverse population with variable TB risks. This may mask important TB epidemiologic trends and not accurately reflect local transmission patterns.

METHODS

We used population-level data from two large cohorts in British Columbia (BC), Canada: an immigration cohort (n = 337,492 permanent residents to BC) and a genotyping cohort (n = 2290 culture-confirmed active TB cases). We stratified active TB case counts, incidence rates, and genotypic clustering (an indicator of TB transmission) in BC by birth country TB incidence, age at immigration, and years since arrival.

RESULTS

Persons from high-incidence countries had a 12-fold higher TB incidence than those emigrating from low-incidence settings. Estimates of local transmission, as captured by genotyping, versus reactivation of latent TB infection acquired outside Canada varied when data were stratified by birthplace TB incidence, as did patient-level characteristics of individuals in each group, such as age and years between immigration and diagnosis.

CONCLUSION

Categorizing persons beyond simply "foreign-born", particularly in the context of TB epidemiologic and molecular data, is needed for a more accurate understanding of TB rates and patterns of transmission.

Tuberculosis among healthcare personnel, United States, 2010-2016

We describe characteristics of US healthcare personnel (HCP) diagnosed with tuberculosis (TB). Among 64,770 adults with TB during 2010-2016, 2,460 (4%) were HCP. HCP with TB were more likely to be born outside of the United States, and less likely to have TB attributed to recent transmission, than non-HCP.

Genome-based transmission modelling separates imported tuberculosis from recent transmission within an immigrant population

In many countries the incidence of tuberculosis (TB) is low and is largely shaped by immigrant populations from high-burden countries. This is the case in Norway, where more than 80 % of TB cases are found among immigrants from high-incidence countries. A variable latent period, low rates of evolution and structured social networks make separating import from within-border transmission a major conundrum to TB control efforts in many low-incidence countries. Clinical Mycobacterium tuberculosis isolates belonging to an unusually large genotype cluster associated with people born in the Horn of Africa have been identified in Norway over the last two decades. We modelled transmission based on whole-genome sequence data to estimate infection times for individual patients. By contrasting these estimates with time of arrival in Norway, we estimate on a case-by-case basis whether patients were likely to have been infected before or after arrival. Independent import was responsible for the majority of cases, but we estimate that about one-quarter of the patients had contracted TB in Norway. This study illuminates the transmission dynamics within an immigrant community. Our approach is broadly applicable to many settings where TB control programmes can benefit from understanding when and where patients acquired TB.

Prospects for Tuberculosis Elimination in the United States: Results of a Transmission Dynamic Model

We estimated long-term tuberculosis (TB) trends in the US population and assessed prospects for TB elimination. We used a detailed simulation model allowing for changes in TB transmission, immigration, and other TB risk determinants. Five hypothetical scenarios were evaluated from 2017 to 2100: 1) maintain current TB prevention and treatment activities (base case); 2) provision of latent TB infection testing and treatment for new legal immigrants; 3) increased uptake of latent TB infection screening and treatment among high-risk populations, including a 3-month isoniazid-rifapentine regimen; 4) improved TB case detection; and 5) improved TB treatment quality. Under the base case, we estimate that by 2050, TB incidence will decline to 14 cases per million, a 52% (95% posterior interval (PI): 35, 67) reduction from 2016, and 82% (95% posterior interval: 78, 86) of incident TB will be among persons born outside of the United States. Intensified TB control could reduce incidence by 77% (95% posterior interval: 66, 85) by 2050. We predict TB may be eliminated in US-born but not non-US-born persons by 2100. Results were sensitive to numbers of people entering the United States with latent or active TB, and were robust to alternative interpretations of epidemiologic evidence. TB elimination in the United States remains a distant goal; however, strengthening TB prevention and treatment could produce important health benefits.

QuantiFERON-TB Gold Plus Is a More Sensitive Screening Tool than QuantiFERON-TB Gold In-Tube for Latent Tuberculosis Infection among Older Adults in Long-Term Care Facilities

We investigated the prevalence of latent tuberculosis infection (LTBI) among the residents in seven long-term care facilities (LTCFs) located in different regions of Taiwan and compared the performance of two interferon gamma release assays, i.e., QuantiFERON-TB Gold In-Tube (QFT-GIT) and QuantiFERON-TB Gold Plus (QFT-Plus) for screening LTBI. We also assessed the diagnostic performance against a composite reference standard (subjects with persistent-positive, transient-positive, and negative results from QFTs during reproducibility analysis were classified as definite, possible, and not LTBI, respectively). Two hundred forty-four residents were enrolled, and 229 subjects were included in the analysis. The median age was 80 years (range, 60 to 102 years old), and 117 (51.1%) were male. Among them, 66 (28.8%) and 74 (32.3%) subjects had positive results from QFT-GIT and QFT-Plus, respectively, and the results for 215 (93.9%) subjects showed agreement. Using the composite reference standard, 66 (28.8%), 11 (4.8%), and 152 (66.4%) were classified as definite, possible, and not LTBI, respectively. For definite LTBI, the sensitivity, specificity, positive predictive value, and negative predictive value of QFT-GIT were 89.4%, 95.7%, 89.4%, and 95.7%, respectively, and those for QFT-Plus were 100.0%, 95.1%, 89.2%, and 100.0%, respectively. The sensitivity of QFT-GIT decreased gradually with patient age. Compared to QFT-GIT, QFT-Plus displayed significantly higher sensitivity (100.0% versus 89.4%, P = 0.013) and similar specificity (95.1% versus 95.7%). In conclusion, a high prevalence of LTBI was found among elders in LTCFs in Taiwan. The new QFT-Plus test demonstrated a higher sensitivity than QFT-GIT in the older adults in LTCFs.

Spatial clusters of latent tuberculous infection, Connecticut, 2010-2014

SETTING

In the United States, tuberculosis (TB) control is increasingly focusing on the identification of persons with latent tuberculous infection (LTBI).

OBJECTIVE

To characterize the local epidemiology of LTBI in Connecticut, USA.

METHODS

We used spatial analyses 1) to identify census tract-level clusters of reported LTBI and TB disease in Connecticut, 2) to compare persons and populations in clusters with those not in clusters, and 3) to compare persons with LTBI to those with TB disease.

RESULTS

Significant census tract-level spatial clusters of LTBI and TB disease were identified. Compared with persons with LTBI in non-clustered census tracts, those in clustered census tracts were more likely to be foreign-born and less likely to be of white non-Hispanic ethnicity. Populations in census tract clusters of high LTBI prevalence had greater crowding, persons living in poverty, and persons lacking health care insurance than populations not in clustered census tracts. Persons with LTBI were less likely than those with TB disease to be of Asian ethnicity, and persons with LTBI were more likely than those with TB disease to reside in a clustered census tract.

CONCLUSIONS

Characterizing fine-scale populations at risk for LTBI supports effective and culturally accessible screening and treatment programs.

Drivers of Tuberculosis Transmission

Measuring tuberculosis transmission is exceedingly difficult, given the remarkable variability in the timing of clinical disease after Mycobacterium tuberculosis infection; incident disease can result from either a recent (ie, weeks to months) or a remote (ie, several years to decades) infection event. Although we cannot identify with certainty the timing and location of tuberculosis transmission for individuals, approaches for estimating the individual probability of recent transmission and for estimating the fraction of tuberculosis cases due to recent transmission in populations have been developed. Data used to estimate the probable burden of recent transmission include tuberculosis case notifications in young children and trends in tuberculin skin test and interferon γ-release assays. More recently, M. tuberculosis whole-genome sequencing has been used to estimate population levels of recent transmission, identify the distribution of specific strains within communities, and decipher chains of transmission among culture-positive tuberculosis cases. The factors that drive the transmission of tuberculosis in communities depend on the burden of prevalent tuberculosis; the ways in which individuals live, work, and interact (eg, congregate settings); and the capacity of healthcare and public health systems to identify and effectively treat individuals with infectious forms of tuberculosis. Here we provide an overview of these factors, describe tools for measurement of ongoing transmission, and highlight knowledge gaps that must be addressed.

Comparing Drivers and Dynamics of Tuberculosis in California, Florida, New York, and Texas

RATIONALE

There is substantial state-to-state heterogeneity in tuberculosis (TB) in the United States; better understanding this heterogeneity can inform effective response to TB at the state level, the level at which most TB control efforts are coordinated.

OBJECTIVES

To characterize drivers of state-level heterogeneity in TB epidemiology in the four U.S. states that bear half the country's TB burden: California, Florida, New York, and Texas.

METHODS

We constructed an individual-based model of TB in the four U.S. states and calibrated the model to state-specific demographic and age- and nativity-stratified TB incidence data. We used the model to infer differences in natural history of TB and in future projections of TB.

MEASUREMENTS AND MAIN RESULTS

We found that differences in both demographic makeup (particularly the size and composition of the foreign-born population) and TB transmission dynamics contribute to state-level differences in TB epidemiology. The projected median annual rate of decline in TB incidence in the next decade was substantially higher in Texas (3.3%; 95% range, -5.6 to 10.9) than in California (1.7%; 95% range, -3.8 to 7.1), Florida (1.5%; 95% range, -7.4 to 14), and New York (1.9%; 95% range, -6.4 to 9.8). All scenarios projected a flattening of the decline in TB incidence by 2025 without additional resources or interventions.

CONCLUSIONS

There is substantial state-level heterogeneity in TB epidemiology in the four states, which reflect both demographic factors and potential differences in the natural history of TB. These differences may inform resource allocation decisions in these states.

Summary of Notifiable Infectious Diseases and Conditions - United States, 2015

The Summary of Notifiable Infectious Diseases and Conditions - United States, 2015 (hereafter referred to as the summary) contains the official statistics, in tabular and graphical form, for the reported occurrence of nationally notifiable infectious diseases and conditions in the United States for 2015. Unless otherwise noted, data are final totals for 2015 reported as of June 30, 2016. These statistics are collected and compiled from reports sent by U.S. state and territories, New York City, and District of Columbia health departments to the National Notifiable Diseases Surveillance System (NNDSS), which is operated by CDC in collaboration with the Council of State and Territorial Epidemiologists (CSTE). This summary is available at https://www.cdc.gov/MMWR/MMWR_nd/index.html. This site also includes summary publications from previous years.