Outbreak of tuberculosis among Guatemalan immigrants in rural Minnesota, 2008

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.

Yield of testing and treatment for tuberculosis among foreign-born persons during contact investigations in the United States: A semi-systematic review

BACKGROUND

Contact investigation is an important strategy for maintaining control of tuberculosis (TB) in the United States. However, testing and treatment outcomes specifically to foreign-born populations are poorly understood. We reviewed literature on testing and LTBI identified during contact investigations in foreign-born populations living in the US.

METHODS

We conducted a comprehensive search of peer-reviewed and grey literature using Cochrane systematic review methods. We included studies with adult and adolescent populations that were at least 50% foreign-born. Pooled proportions and 95% confidence intervals (CIs) were calculated via inverse-variance weighted meta-analysis, and cumulative proportions were calculated as products of adjacent step proportions.

RESULTS

We identified 22 studies published between 1997 and 2014 that included at least 50% foreign-born participants. From studies of predominantly (>90%) foreign-born populations, almost all identified contacts were recruited and had valid test results, and 54.8% (95% CI 45.1-62.5%) of contacts with valid test results tested positive. From studies of majority (50% to 90%) foreign-born populations, 78.4% (95% CI 78.0-78.9%) of identified contacts were recruited, 92.0% (95% CI 91.6-92.3%) of recruited contacts had valid test results, and 38.5% (95% CI 31.9%-44.2%) of persons with valid results tested positive. These proportions varied by test type in studies of predominantly foreign-born populations. For every 1000 contacts identified in predominantly foreign-born populations, we estimate that 535 (95% CI 438 to 625) will test positive, and 354 (95% CI 244 to 453) will complete LTBI treatment. For every 1000 contacts identified in majority foreign-born populations, these estimates are 276 (95% CI 230 to 318), and 134 (95% CI 44 to 264), respectively.

CONCLUSIONS

Contact investigation is a high yield activity for identifying and treating foreign-born persons with LTBI, but must be complemented by other tuberculosis control activities in order to achieve continued progress toward TB elimination.

Disparities in Tuberculosis Treatment Completion by Incarceration Status, U.S., 1999-2011

INTRODUCTION

Treatment completion is the cornerstone of tuberculosis (TB) control strategy globally. Although the majority of reported TB cases in the U.S. have documented treatment completion, individuals diagnosed while incarcerated are less likely to have documentation of whether or not they completed treatment. This study assessed trends and correlates of no documented treatment completion among individuals incarcerated at diagnosis.

METHODS

U.S. National TB Surveillance System (1999-2011) data on cases eligible for treatment completion were analyzed during 2014-2015. Treatment outcomes and trends in no documented completion were assessed by incarceration status. Multivariable logistic regression identified correlates of no documented completion among people incarcerated at diagnosis.

RESULTS

A lower proportion of individuals incarcerated at diagnosis had documented TB treatment completion than non-incarcerated individuals (75.6% vs 93.7%), and a higher proportion were lost to follow-up (10.7% vs 2.2%) or moved (9.4% vs 2.3%) during treatment (p<0.001). The 1999-2011 trend in no documented completion significantly increased among those incarcerated at diagnosis and declined among non-incarcerated individuals. Being foreign born was the strongest correlate of no documented completion among people incarcerated at diagnosis (AOR=2.86, 95% CI= 2.35, 3.49). Social risk factors for TB (e.g., homelessness, substance abuse), although common among incarcerated individuals, did not emerge as correlates of no documented completion.

CONCLUSIONS

People diagnosed with TB disease at U.S. correctional facilities, especially the foreign born, require enhanced strategies for documenting TB treatment completion. Strengthened collaboration between correctional and public health agencies could improve continuity of care among released inmates.

Whole-genome sequencing in outbreak analysis

In addition to the ever-present concern of medical professionals about epidemics of infectious diseases, the relative ease of access and low cost of obtaining, producing, and disseminating pathogenic organisms or biological toxins mean that bioterrorism activity should also be considered when facing a disease outbreak. Utilization of whole-genome sequencing (WGS) in outbreak analysis facilitates the rapid and accurate identification of virulence factors of the pathogen and can be used to identify the path of disease transmission within a population and provide information on the probable source. Molecular tools such as WGS are being refined and advanced at a rapid pace to provide robust and higher-resolution methods for identifying, comparing, and classifying pathogenic organisms. If these methods of pathogen characterization are properly applied, they will enable an improved public health response whether a disease outbreak was initiated by natural events or by accidental or deliberate human activity. The current application of next-generation sequencing (NGS) technology to microbial WGS and microbial forensics is reviewed.

A tuberculosis outbreak fueled by cross-border travel and illicit substances: Nevada and Arizona

OBJECTIVES

From May 2006 to August 2008, the Southern Nevada Health District identified eight tuberculosis (TB) cases in six adults and two children in a Hispanic community. We conducted an outbreak investigation to determine the extent of TB transmission and prevent additional cases.

METHODS

We investigated TB cases in Nevada and Arizona with the outbreak genotype or cases with suspected epidemiologic links to this cluster but without genotyping data. We reviewed medical records and interviewed patients and contacts. Subsequently, genotype surveillance was conducted for approximately four years to monitor additional outbreak-related cases.

RESULTS

Eight outbreak cases were identified among six adults and two children. All patients were Hispanic and five were U.S.-born. The index patient was diagnosed while detained in Immigration and Customs Enforcement custody but deported before treatment completion. He was lost to follow-up for two years, during which time he served as the source for six secondary TB cases, including his own child. Along with the index patient, five patients reportedly engaged in the sale or use of methamphetamine. Follow-up surveillance in the two states identified eight additional cases with the outbreak genotype; three had epidemiologic links to the index case.

CONCLUSIONS

We found that incomplete TB treatment led to extensive TB transmission. We recommend thorough discharge planning and active measures to ensure continuity of care and TB treatment completion for people in custody at higher risk for loss to follow-up, which likely includes those engaged in the sale or use of illicit substances.

Using routinely reported tuberculosis genotyping and surveillance data to predict tuberculosis outbreaks

We combined routinely reported tuberculosis (TB) patient characteristics with genotyping data and measures of geospatial concentration to predict which small clusters (i.e., consisting of only 3 TB patients) in the United States were most likely to become outbreaks of at least 6 TB cases. Of 146 clusters analyzed, 16 (11.0%) grew into outbreaks. Clusters most likely to become outbreaks were those in which at least 1 of the first 3 patients reported homelessness or excess alcohol or illicit drug use or was incarcerated at the time of TB diagnosis and in which the cluster grew rapidly (i.e., the third case was diagnosed within 5.3 months of the first case). Of 17 clusters with these characteristics and therefore considered high risk, 9 (53%) became outbreaks. This retrospective cohort analysis of clusters in the United States suggests that routinely reported data may identify small clusters that are likely to become outbreaks and which are therefore candidates for intensified contact investigations.