I am a postdoctoral research fellow focusing on infectious disease epidemiology, specifically tuberculosis, in the Division of Infectious Diseases and Geographic Medicine at Stanford University's School of Medicine under the mentorship of Dr. Jason Andrews.
My research focuses on
(i) deriving and validating meaningful and effective interventions to diagnose and prevent pediatric tuberculosis
(ii) furthering our understanding of tuberculosis transmission dynamics in high-burden settings, and
(iii) advocating for the implementation of effective health policy in low-income communities with a high tuberculosis burden
Honors & Awards
2017 Stephen Lawn TB-HIV Research Leadership Prize, TB Centre at LSHTM in London, UK, Desmond Tutu HIV Centre in Cape Town, South Africa, & The Union
BA, University of Arizona, Political Science, Spanish (2009)
MPH, Tulane University, School of Public Health and Tropical Medicine, Global Community Health and Behavioral Sciences (2012)
PhD, University of Georgia School of Public Health, Epidemiology (2017)
Paediatric tuberculosis transmission outside the household: challenging historical paradigms to inform future public health strategies.
The Lancet. Respiratory medicine
Tuberculosis is a major cause of death and disability among children globally, yet children have been neglected in global tuberculosis control efforts. Historically, tuberculosis in children has been thought of as a family disease, and because of this, household contact tracing of children after identification of an adult tuberculosis case has been emphasised as the principal public health intervention. However, the population-level effect of household contact tracing is predicated on the assumption that most paediatric tuberculosis infections are acquired within the household. In this Personal View, we focus on accumulating scientific evidence indicating that the majority of Mycobacterium tuberculosis transmission to children in high-burden settings occurs in the community, outside of households in which a person has tuberculosis. We estimate the population-attributable fraction of M tuberculosis transmission to children due to household exposures to be between 10% and 30%. M tuberculosis transmission from the household was low (<30%) even in children younger than age 5 years. We propose that an effective public health response to childhood tuberculosis requires comprehensive, community-based interventions, such as active surveillance in select settings, rather than contact tracing alone. Importantly, the historical paradigm that most paediatric transmission occurs in households should be reconsidered on the basis of the scientific knowledge presented.
View details for PubMedID 31078497
Advances in the understanding of Mycobacterium tuberculosis transmission in HIV-endemic settings.
The Lancet. Infectious diseases
Tuberculosis claims more human lives than any other infectious disease. This alarming epidemic has fuelled the development of novel antimicrobials and diagnostics. However, public health interventions that interrupt transmission have been slow to emerge, particularly in HIV-endemic settings. Transmission of tuberculosis is complex, involving various environmental, bacteriological, and host factors, among which concomitant HIV infection is important. Preventing person-to-person spread is central to halting the epidemic and, consequently, tuberculosis transmission is now being studied with renewed interest. In this Series paper, we review recent advances in the understanding of tuberculosis transmission, from the view of source-case infectiousness, inherent susceptibility of exposed individuals, appending tools for predicting risk of disease progression, the biophysical nature of the contagion, and the environments in which transmission occurs and is sustained in populations. We focus specifically on how HIV infection affects these features with a view to describing novel transmission blocking strategies in HIV-endemic settings.
View details for PubMedID 30554995
- Tuberculin skin test conversion and primary progressive tuberculosis disease in the first 5 years of life: a birth cohort study from Cape Town, South Africa The Lancet Child & Adolescent Health 2018; 2 (1): 46-55.
Transmission of Mycobacterium Tuberculosis in Households and the Community: A Systematic Review and Meta-Analysis.
American journal of epidemiology
2017; 185 (12): 1327–39
The individual- and population-level impact of household tuberculosis exposure on transmission is unclear but may have implications for the effectiveness and implementation of control interventions. We systematically searched for and included studies in which latent tuberculosis infection was assessed in 2 groups: children exposed and unexposed to a household member with tuberculosis. We also extracted data on the smear and culture status of index cases, the age and bacillus Calmette-Guérin vaccination status of contacts, and study design characteristics. Of 6,176 citations identified from our search strategy, 26 studies (13,999 children with household exposure to tuberculosis and 174,097 children without) from 1929-2015 met inclusion criteria. Exposed children were 3.79 (95% confidence interval (CI): 3.01, 4.78) times more likely to be infected than were their community counterparts. Metaregression demonstrated higher infection among children aged 0-4 years of age compared with children aged 10-14 years (ratio of odds ratios = 2.24, 95% CI: 1.43, 3.51) and among smear-positive versus smear-negative index cases (ratio of odds ratios = 5.45, 95% CI: 3.43, 8.64). At the population level, we estimated that a small proportion (<20%) of transmission was attributable to household exposure. Our results suggest that targeting tuberculosis prevention efforts to household contacts is highly effective. However, a large proportion of transmission at the population level may occur outside the household.
View details for DOI 10.1093/aje/kwx025
View details for PubMedID 28982226
Effectiveness of WHO's pragmatic screening algorithm for child contacts of tuberculosis cases in resource-constrained settings: a prospective cohort study in Uganda.
The Lancet. Respiratory medicine
Tuberculosis is a leading cause of global childhood mortality; however, interventions to detect undiagnosed tuberculosis in children are underused. Child contact tracing has been widely recommended but poorly implemented in resource-constrained settings. WHO has proposed a pragmatic screening approach for managing child contacts. We assessed the effectiveness of this screening approach and alternative symptom-based algorithms in identifying secondary tuberculosis in a prospectively followed cohort of Ugandan child contacts.We identified index patients aged at least 18 years with microbiologically confirmed pulmonary tuberculosis at Old Mulago Hospital (Kampala, Uganda) between Oct 1, 1995, and Dec 31, 2008. Households of index patients were visited by fieldworkers within 2 weeks of diagnosis. Coprevalent and incident tuberculosis were assessed in household contacts through clinical, radiographical, and microbiological examinations for 2 years. Disease rates were compared among children younger than 16 years with and without symptoms included in the WHO pragmatic guideline (presence of haemoptysis, fever, chronic cough, weight loss, night sweats, and poor appetite). Symptoms could be of any duration, except cough (>21 days) and fever (>14 days). A modified WHO decision-tree designed to detect high-risk asymptomatic child contacts was also assessed, in which all asymptomatic contacts were classified as high risk (children younger than 3 years or immunocompromised [HIV-infected]) or low risk (aged 3 years or older and immunocompetent [HIV-negative]). We also assessed a more restrictive algorithm (ie, assessing only children with presence of chronic cough and one other tuberculosis-related symptom).Of 1718 household child contacts, 126 (7%) had coprevalent tuberculosis and 24 (1%) developed incident tuberculosis, diagnosed over the 2-year study period. Of these 150 cases of tuberculosis, 95 (63%) were microbiologically confirmed with a positive sputum culture. Using the WHO approach, 364 (21%) of 1718 child contacts had at least one tuberculosis-related symptom and 85 (23%) were identified as having coprevalent tuberculosis, 67% of all coprevalent cases detected (diagnostic odds ratio 9·8, 95% CI 6·8-14·5; p<0·0001). 1354 (79%) of 1718 child contacts had no symptoms, of whom 41 (3%) had coprevalent tuberculosis. The WHO approach was effective in contacts younger than 5 years: 70 (33%) of 211 symptomatic contacts had coprevalent disease compared with 23 (6%) of 367 asymptomatic contacts (p<0·0001). This approach was also effective in contacts aged 5 years and older: 15 (10%) of 153 symptomatic contacts had coprevalent disease compared with 18 (2%) of 987 asymptomatic contacts (p<0·0001). More coprevalent disease was detected in child contacts recommended for screening when the study population was restricted by HIV-serostatus (11 [48%] of 23 symptomatic HIV-seropositive child contacts vs two [7%] of 31 asymptomatic HIV-seropositive child contacts) or to only culture-confirmed cases (47 [13%] culture confirmed cases of 364 symptomatic child contacts vs 29 [2%] culture confirmed cases of 1354 asymptomatic child contacts). In the modified algorithm, high-risk asymptomatic child contacts were at increased risk for coprevalent disease versus low-risk asymptomatic contacts (14 [6%] of 224 vs 27 [2%] of 1130; p=0·0021). The presence of tuberculosis infection did not predict incident disease in either symptomatic or asymptomatic child contacts: in symptomatic contacts, eight (5%) of 169 infected contacts and six (5%) of 111 uninfected contacts developed incident tuberculosis (p=0·80). Among asymptomatic contacts, incident tuberculosis occurred in six (<1%) of 795 contacts infected at baseline versus four (<1%) of 518 contacts uninfected at baseline, respectively (p=1·00).WHO's pragmatic, symptom-based algorithm was an effective case-finding tool, especially in children younger than 5 years. A modified decision-tree identified 6% of asymptomatic child contacts at high risk for subclinical disease. Increasing the feasibility of child-contact tracing using these approaches should be encouraged to decrease tuberculosis-related paediatric mortality in high-burden settings, but this should be partnered with increasing access to microbiological point-of-care testing.National Institutes of Health, Tuberculosis Research Unit, AIDS International Training and Research Program of the Fogarty International Center, and the Center for AIDS Research.
View details for DOI 10.1016/S2213-2600(17)30497-6
View details for PubMedID 29273539
Infectiousness of HIV-Seropositive Patients with Tuberculosis in a High-Burden African Setting
AMERICAN JOURNAL OF RESPIRATORY AND CRITICAL CARE MEDICINE
2016; 194 (9): 1152-1163
Policy recommendations on contact investigation of HIV-seropositive patients with tuberculosis have changed several times. Current epidemiologic evidence informing these recommendations is considered low quality, and few large studies investigating the infectiousness of HIV-seropositive and -seronegative index cases have been performed in sub-Saharan Africa.We assessed the infectiousness of HIV-seropositive and -seronegative patients with tuberculosis to their household contacts and examined potential modifiers of this relationship.Adults suffering from their first episode of pulmonary tuberculosis were identified in Kampala, Uganda. Field workers visited index households and enrolled consenting household contacts. Latent tuberculosis infection was measured through tuberculin skin testing, and relative risks were calculated using modified Poisson regression models. Standard assessments of interaction between latent tuberculosis infection, the HIV serostatus of index cases, and other variables were performed.Latent tuberculosis infection was found in 577 of 878 (65.7%) and 717 of 974 (73.6%) household contacts of HIV-seropositive and -seronegative tuberculosis cases (relative risk, 0.89; 95% confidence interval, 0.82-0.97). On further stratification, cavitary lung disease (P < 0.0001 for interaction) and smear status (P = 0.02 for interaction) of tuberculosis cases modified the infectiousness of HIV-seropositive indexes. Cough duration of index cases did not display interaction (P = 0.499 for interaction).This study suggests that HIV-seropositive tuberculosis cases may be less infectious than HIV-seronegative patients only when they are smear-negative or lack cavitary lung disease. These results may explain heterogeneity between prior studies and provide evidence suggesting that tuberculosis contact investigation should include HIV-seropositive index cases in high disease burden settings.
View details for DOI 10.1164/rccm.201511-2146OC
View details for Web of Science ID 000386866600018
View details for PubMedID 27181053
View details for PubMedCentralID PMC5114446
- Towards a more holistic understanding of paediatric tuberculosis LANCET CHILD & ADOLESCENT HEALTH 2019; 3 (4): 220–21
Detection, survival and infectious potential of Mycobacterium tuberculosis in the environment: A review of the evidence and epidemiological implications.
The European respiratory journal
Much remains unknown about Mycobacterium tuberculosis transmission. Seminal experimental studies from the 1950s demonstrated that airborne expulsion of droplet nuclei from an infectious tuberculosis patient is the primary route of transmission. However, these findings did not rule out other routes of M. tuberculosis transmission. We reviewed historical scientific evidence from the late 19th and early 20th century and contemporary studies investigating the presence, persistence, and infectiousness of environmental M. tuberculosis We found evidence - both experimental and epidemiological - supporting the presence and viability of M. tuberculosis in multiple natural and built environments for months to years, presumably following contamination by a human source. Further, several studies confirm M. tuberculosis viability and virulence in the environment using guinea pig and mouse models. Most of this evidence was historical; however, several recent studies have reported consistent findings of M. tuberculosis detection and viability in the environment using modern methods. Whether or not M. tuberculosis in environments represents an infectious threat to humans, it may represent an untapped source of data with which to further understand M. tuberculosis transmission. We discuss potential opportunities for harnessing these data to generate new insights into tuberculosis transmission in congregate settings.
View details for PubMedID 31048345
Improving Tuberculosis Case Finding in Persons Living with Advanced HIV through New Diagnostic Algorithms.
American journal of respiratory and critical care medicine
View details for PubMedID 30273498
Cognitive deficits and educational loss in children with schistosome infection-A systematic review and meta-analysis.
PLoS neglected tropical diseases
2018; 12 (1): e0005524
By means of meta-analysis of information from all relevant epidemiologic studies, we examined the hypothesis that Schistosoma infection in school-aged children (SAC) is associated with educational loss and cognitive deficits.This review was prospectively registered in the PROSPERO database (CRD42016040052). Medline, Biosis, and Web of Science were searched for studies published before August 2016 that evaluated associations between Schistosoma infection and cognitive or educational outcomes. Cognitive function was defined in four domains-learning, memory, reaction time, and innate intelligence. Educational outcome measures were defined as attendance and scholastic achievement. Risk of bias (ROB) was evaluated using the Newcastle-Ottawa quality assessment scale. Standardized mean differences (SMD) and 95% confidence intervals (CI) were calculated to compare cognitive and educational measures for Schistosoma infected /not dewormed vs. uninfected/dewormed children. Sensitivity analyses by study design, ROB, and sequential exclusion of individual studies were implemented. Thirty studies from 14 countries, including 38,992 SAC between 5-19 years old, were identified. Compared to uninfected children and children dewormed with praziquantel, the presence of Schistosoma infection and/or non-dewormed status was associated with deficits in school attendance (SMD = -0.36, 95%CI: -0.60, -0.12), scholastic achievement (SMD = -0.58, 95%CI: -0.96, -0.20), learning (SMD = -0.39, 95%CI: -0.70, -0.09) and memory (SMD = -0.28, 95%CI: -0.52, -0.04) tests. By contrast, Schistosoma-infected/non-dewormed and uninfected/dewormed children were similar with respect to performance in tests of reaction time (SMD = -0.06, 95%CI: -0.42, 0.30) and intelligence (SMD = -0.25, 95%CI: -0.57, 0.06). Schistosoma infection-associated deficits in educational measures were robust among observational studies, but not among interventional studies. The significance of infection-associated deficits in scholastic achievement was sensitive to ROB. Schistosoma infection-related deficits in learning and memory tests were invariant by ROB and study design.Schistosoma infection/non-treatment was significantly associated with educational, learning, and memory deficits in SAC. Early treatment of children in Schistosoma-endemic regions could potentially mitigate these deficits.ClinicalTrials.gov CRD42016040052.
View details for DOI 10.1371/journal.pntd.0005524
View details for PubMedID 29329293
Tuberculin conversion and tuberculosis disease in infants and young children from the Drakenstein Child Health Study: A call to action.
South African medical journal = Suid-Afrikaanse tydskrif vir geneeskunde
2018; 108 (4): 247–48
Although tuberculosis (TB) is widely acknowledged as a major driver of global morbidity and mortality in adults, the disease's impact on children has been underappreciated. Global estimates of mortality among children aged <5 years, derived largely from vital registration and verbal autopsy records, have excluded paediatric TB as a contributing cause.
View details for DOI 10.7196/SAMJ.2017.v108i4.13169
View details for PubMedID 29629670
Factors affecting time to sputum culture conversion and treatment outcome of patients with multidrug-resistant tuberculosis in China.
BMC infectious diseases
2018; 18 (1): 114
Few prospective cohort studies, none in China, have investigated the relationship between treatment outcomes of multidrug-resistant tuberculosis (MDR-TB) patients and sputum culture conversion. Factors affecting the time of the culture conversion throughout the whole course of the treatment have rarely been investigated.This study was performed in four cities in Jiangsu province, China. MDR-TB patients were consecutively enrolled between December 2011 and March 2014. Rates of sputum culture conversion were calculated and Cox proportional-hazards model was performed. Factors contributing to sputum culture conversion were investigated.In all, 139 MDR-TB patients with treatment outcomes were enrolled. Median time to culture conversion among those who converted was 91.5 days (interquartile range, 34.0-110.8 days). After multivariable analysis, smoking (HR = 0.44; 95% CI: 0.23-0.83), drinking (HR = 0.41; 95% CI: 0.21-0.81), ofloxacin resistance (HR = 0.43; 95% CI: 0.24-0.76) and sputum smear grade > 1 (HR = 0.51; 95% CI: 0.31-0.83) were less likely to have culture conversion.MDR-TB patients who smoke, drink, have ofloxacin resistance, or a high smear grade are less likely to respond to treatment and should be meticulously followed up.
View details for DOI 10.1186/s12879-018-3021-0
View details for PubMedID 29510666
Low Prevalence of Tuberculin Skin Test Boosting among Community Residents in Uganda.
The American journal of tropical medicine and hygiene
Boosted tuberculin skin test (TST) reactions can be misclassified as new latent tuberculosis (TB) infection. To our knowledge, no study has evaluated the prevalence of TST boosting in a population-based sample in high TB burden settings. We determined the prevalence of TST boosting among urban residents in Uganda. We evaluated 99 participants with initial TST < 5 mm and repeated a skin test after 2 weeks. We found that only 2% had boosted TST reactions suggesting that most TST conversions could represent new TB infections in this high-burden setting.
View details for DOI 10.4269/ajtmh.17-0591
View details for PubMedID 29313483
Performance of the QuantiFERON®-TB Gold In-Tube assay in tuberculin skin test converters: a prospective cohort study.
The international journal of tuberculosis and lung disease : the official journal of the International Union against Tuberculosis and Lung Disease
2018; 22 (9): 1000–1006
To investigate diagnostic agreement of the QuantiFERON®-TB Gold In-Tube (QFT-GIT) test in adult tuberculin skin test (TST) converters in a high tuberculosis (TB) burden setting.We performed a case-cohort study from 2014 to 2016 in Uganda among residents who were not infected with Mycobacterium tuberculosis. Participants were followed up for 1 year, when they were retested to determine TST conversion. All TST converters and a random sample of participants from baseline were offered QFT-GIT testing.Of 368 enrolled participants, 61 (17%) converted their TST by 1 year. Among 61 converters, 42 were tested using QFT-GIT, 64% of whom were QFT-GIT-positive. Of 307 participants with a persistent negative TST, 48 were tested using QFT-GIT, 83% of whom were QFT-negative. Overall concordance of TST and QFT-GIT was moderate (κ = 0.48, 95%CI 0.30-0.66). Converters with a conversion of 15 mm had a higher proportion of concordant QFT-GIT results (79%) than converters with increments of 10-14.9 mm (52%).Concordance between TST and QFT-GIT was moderate among TST converters in this urban African population. These findings call for improved tests that more accurately measure conversion to tuberculous infection.
View details for DOI 10.5588/ijtld.18.0073
View details for PubMedID 30092864
View details for PubMedCentralID PMC6482451
) in urban school microenvironments near a contaminated beach with mine tailings, Chañaral, Chile.
Environmental geochemistry and health
Air quality in schools is an important public health issue because children spend a considerable part of their daily life in classrooms. Particulate size and chemical composition has been associated with negative health effects. We studied levels of trace element concentrations in fine particulate matter (PM2.5) in indoor versus outdoor school settings from six schools in Chañaral, a coastal city with a beach severely polluted with mine tailings. Concentrations of trace elements were measured on two consecutive days during the summer and winter of 2012 and 2013 and determined using X-ray fluorescence. Source apportionment and element enrichment were measured using principal components analysis and enrichment factors. Trace elements were higher in indoor school spaces, especially in classrooms compared with outdoor environments. The most abundant elements were Na, Cl, S, Ca, Fe, K, Mn, Ti, and Si, associated with earth's crust. Conversely, an extremely high enrichment factor was determined for Cu, Zn, Ni and Cr; heavy metals associated with systemic and carcinogenic risk effects, whose probably origin sources are industrial and mining activities. These results suggest that the main source of trace elements in PM2.5 from these school microenvironments is a mixture of dust contaminated with mine tailings and marine aerosols. Policymakers should prioritize environmental management changes to minimize further environmental damage and its direct impact on the health of children exposed.
View details for DOI 10.1007/s10653-017-9980-z
View details for PubMedID 28536962
- Time to sputum culture conversion and treatment outcome of patients with multidrug-resistant tuberculosis: a prospective cohort study from urban China EUROPEAN RESPIRATORY JOURNAL 2017; 49 (3)
- Innovative Methods to Manage, Detect, and Prevent Tuberculosis. American journal of respiratory and critical care medicine 2017; 195 (4): 530-532
Delays and Pathways to Final Tuberculosis Diagnosis in Patients from a Referral Hospital in Urban China.
The American journal of tropical medicine and hygiene
AbstractChina is among the countries with the largest epidemic of drug susceptible and resistant tuberculosis globally. We investigated the locations tuberculosis patients visited before being diagnosed, total diagnostic delay, and risk factors associated with total delay from a large tuberculosis referral hospital in Nanjing, China. We conducted a retrospective cohort study among tuberculosis patients who initiated anti-tuberculosis treatment within 3 months prior to the study date. Patient information regarding time and locations visited while seeking care for tuberculosis-related symptoms was collected through face-to-face interviews. Crude and adjusted Cox proportional hazard ratios of factors associated with time to diagnosis were calculated. Of 179 bacteriologically confirmed patients, 37% were women and median age was 41 (interquartile range [IQR], 26-62). Public hospitals were the most commonly visited health-care institution and repeated visits to them were common. The mean days to tuberculosis diagnosis were 50.3. Female patients (hazard ratio [HR], 1.29; 95% confidence interval [CI], 1.04-1.48) or patients who contacted a health-care provider 2 weeks after becoming symptomatic (HR, 1.59; 95% CI, 1.43-1.70) were significantly less likely to have a timely diagnosis. In a referral hospital in urban China, we found that female tuberculosis patients took significantly more time to reach diagnosis than males and patients often cycled in public hospitals for multiple visits before reaching final diagnosis. Health professionals at public hospitals in Nanjing should be encouraged to refer potential tuberculosis patients as soon as possible to avoid nosocomial transmission.
View details for DOI 10.4269/ajtmh.16-0358
View details for PubMedID 28193742
View details for PubMedCentralID PMC5417195
Diagnostic Performance of the GenoType MTBDRplus and MTBDRsl Assays to Identify Tuberculosis Drug Resistance in Eastern China.
Chinese medical journal
2017; 130 (13): 1521–28
The WHO recently has recommended the GenoType MTBDRplus version 1.0 and MTBDRsl version 1.0 assays for widespread use in countries endemic with drug-resistant tuberculosis. Despite this, these assays have rarely been evaluated in China, where the burden of drug-resistant tuberculosis is among the highest globally.Mycobacterium tuberculosis clinical isolates were obtained between January 2008 and December 2008. Isolates were tested for drug resistance against rifampicin (RFP) and isoniazid (INH) using the GenoType MTBDRplus assay and drug resistance against ethambutol (EMB), ofloxacin (OFX), and kanamycin (KM) using the Genotype MTBDRsl assay. These results were compared with conventional drug-susceptibility testing (DST).Readable results were obtained from 235 strains by GenoType MTBDRplus assay. Compared to DST, the sensitivity of GenoType MTBDRplus assay to detect RFP, INH, and multidrug resistance was 97.7%, 69.9%, and 69.8%, respectively, whereas the specificity for detecting RFP, INH, and multidrug resistance was 66.7%, 69.2%, and 76.8%, respectively. The sensitivity and specificity of the GenoType MTBDRsl assay were 90.9% and 95.2% for OFX, 77.8% and 99.5% for KM, 63.7% and 86.4% for EMB, respectively. Mutations in codon S531L of the rpoB gene and codon S315T1 of KatG gene were dominated in multidrug-resistant tuberculosis (MDR-TB) strains.In combination with DST, application of the GenoType MTBDRplus and MTBDRsl assays may be a useful supplementary tool to allow a rapid and safe diagnosis of multidrug resistance and extensively drug-resistant tuberculosis.
View details for DOI 10.4103/0366-6999.208248
View details for PubMedID 28639565
Mediating Effect of Repeated Tuberculosis Exposure on the Risk of Transmission to Household Contacts of Multidrug-Resistant Tuberculosis Patients.
The American journal of tropical medicine and hygiene
Primary Mycobacterium tuberculosis transmission is an important driver of the global epidemic of resistance to tuberculosis drugs. A few studies have compared tuberculosis infection in contacts of index cases with different drug-resistant profiles, suggesting that contacts of multidrug-resistant (MDR) tuberculosis cases are at higher risk. Repeated tuberculosis exposure in contacts of MDR tuberculosis patients through recurrent tuberculosis may modify this relationship. We compared tuberculosis infection in household contacts of MDR and drug-susceptible (DS) tuberculosis patients from six cities in southeastern China and investigated whether repeated tuberculosis exposure was a mediating factor. Tuberculosis infection was defined as a tuberculin skin test induration ≥ 10 mm. In all, 111 (28.0%) of 397 household contacts of MDR tuberculosis patients and 165 (24.7%) of 667 contacts of DS tuberculosis index cases were infected with tuberculosis. In a multivariate model not including the previous tuberculosis exposure, contacts of MDR tuberculosis patients had a higher likelihood of tuberculosis infection (adjusted odds ratio [AOR] = 1.37; 95% confidence interval [CI] = 1.01-1.84; P = 0.041). In a separate multivariate model adjusted for the previous tuberculosis exposure, the odds ratio of tuberculosis infection flipped and contacts of MDR cases were now at lower risk for tuberculosis infection (AOR = 0.55; 95% CI = 0.38-0.81; P = 0.003). These findings suggest prior tuberculosis exposure in contacts strongly mediates the relationship between tuberculosis infection and the index drug resistance profile. Prior studies showing lower risk of developing tuberculosis among contacts of MDR tuberculosis patients may be partially explained by a lower rate of tuberculosis infection at baseline.
View details for DOI 10.4269/ajtmh.17-0325
View details for PubMedID 29210348
Glycemic Control and the Prevalence of Tuberculosis Infection: A Population-based Observational Study.
Clinical infectious diseases : an official publication of the Infectious Diseases Society of America
2017; 65 (12): 2060–68
Several cohort studies demonstrate that diabetics are at increased risk for active tuberculosis, and poor glycemic control may exacerbate this risk. A higher prevalence of tuberculosis infection at baseline among diabetics may partially explain these results; however, no population-based studies have investigated this association. Furthermore, whether glycemic control modifies the relationship between diabetes and tuberculosis infection, as it does with active tuberculosis, is unknown.Diabetics were diagnosed through physician evaluation and using 3 laboratory tests including hemoglobin A1C (HbA1C), fasting plasma glucose (FPG), or 2-hour plasma glucose (PG). Tuberculosis infection was diagnosed through tuberculin skin tests, and glycemic control was assessed linearly and categorically using recommended targets.Among 4215 participants, the prevalence of tuberculosis infection was 4.1%, 5.5%, and 7.6% in nondiabetic, prediabetic, and diabetic participants (Ptrend = .012). In multivariate analysis, diabetes was associated with tuberculosis infection (adjusted odds ratio [AOR], 1.5; 95% confidence interval [CI], 1.0-2.2). Compared to nondiabetics, diabetics who were undiagnosed (AOR, 2.2 and 1.2 in diagnosed diabetics), FPG >130 mg/dL (AOR, 2.6 and 1.3 in diabetics with FPG ≤130 mg/dL), or not on insulin (AOR, 1.7 and 0.8 in diabetics on insulin) had elevated tuberculosis infection rates. In a linear dose-response analysis, increasing values of FPG (AOR, 1.02 per 1-mg/dL; 95% CI, 1.01-1.03), PG (AOR, 1.02 per 1-mg/dL; 95% CI, 1.01-1.04), and HbA1C (AOR, 1.13 per 1%; 95% CI, 1.04-1.22) all predicted tuberculosis infection.Our results suggest glycemic control may modify the relationship between tuberculosis infection and diabetes.
View details for DOI 10.1093/cid/cix632
View details for PubMedID 29059298
- A Prospective Validation of a Clinical Algorithm to Detect Tuberculosis in Child Contacts. American journal of respiratory and critical care medicine 2017
Four Degrees of Separation: Social Contacts and Health Providers Influence the Steps to Final Diagnosis of Active Tuberculosis Patients in Urban Uganda
BMC INFECTIOUS DISEASES
Delay in tuberculosis (TB) diagnosis adversely affects patients' outcomes and prolongs transmission in the community. The influence of social contacts on steps taken by active pulmonary TB patients to seek a diagnosis has not been well examined.A retrospective study design was use to enroll TB patients on treatment for 3 months or less and aged ≥18 years from 3 public clinics in Kampala, Uganda, from March to July 2014. Social network analysis was used to collect information about social contacts and health providers visited by patients to measure the number of steps and time between onset of symptoms and final diagnosis of TB.Of 294 TB patients, 58 % were male and median age was 30 (IQR: 24-38) years. The median number of steps was 4 (IQR: 3, 7) corresponding to 70 (IQR: 28,140) days to diagnosis. New patients had more steps and time to diagnosis compared retreatment patients (5 vs. 3, P < 0.0001; 84 vs. 46 days P < 0.0001). Fifty-eight percent of patients first contacted persons in their social network. The first step to initiate seeking care accounted for 41 % of the patients' time to diagnosis while visits to non-TB providers and TB providers (without a TB diagnosis) accounted for 34 % and 11 % respectively. New TB patients vs. retreatment (HR: 0.66, 95 % CI; 1.11, 1.99), those who first contacted a non-TB health provider vs. contacting social network (HR: 0.72 95 % CI; 0.55, 0.95) and HIV seronegative vs. seropositive patients (HR: 0.70, 95 % CI; 0.53, 0.92) had a significantly lower likelihood of a timely final diagnosis.There were four degrees of separation between the onset of symptoms in a TB patient and a final diagnosis. Both social and provider networks of patients influenced the diagnostic pathways. Most delays occurred in the first step which represents decisions to seek help, and through interactions with non-TB health providers. TB control programs should strengthen education and active screening in the community and in health care settings to ensure timely diagnosis of TB.
View details for DOI 10.1186/s12879-015-1084-8
View details for Web of Science ID 000359764700005
View details for PubMedID 26293293
View details for PubMedCentralID PMC4546132
Age, sex, and nutritional status modify the CD4+T-cell recovery rate in HIV-tuberculosis co-infected patients on combination antiretroviral therapy
INTERNATIONAL JOURNAL OF INFECTIOUS DISEASES
2015; 35: 73-79
Baseline age and combination antiretroviral therapy (cART) were examined as determinants of CD4+ T-cell recovery during 6 months of tuberculosis (TB) therapy with/without cART. It was determined whether this association was modified by patient sex and nutritional status.This longitudinal analysis included 208 immune-competent, non-pregnant, ART-naive HIV-positive patients from Uganda with a first episode of pulmonary TB. CD4+ T-cell counts were measured using flow cytometry. Age was defined as ≤24, 25-29, 30-34, and 35-39 vs. ≥40 years. Nutritional status was defined as normal (>18.5kg/m(2)) vs. underweight (≤18.5kg/m(2)) using the body mass index (BMI). Multivariate random effects linear mixed models were fitted to estimate differences in CD4+ T-cell recovery in relation to specified determinants.cART was associated with a monthly rise of 15.7 cells/μl (p<0.001). Overall, age was not associated with CD4+ T-cell recovery during TB therapy (p = 0.655). However, among patients on cART, the age-associated CD4+ T-cell recovery rate varied by sex and nutritional status, such that age <40 vs. ≥40 years predicted superior absolute CD4+ T-cell recovery among females (p=0.006) and among patients with a BMI ≥18.5kg/m(2) (p<0.001).TB-infected HIV-positive patients aged ≥40 years have a slower rate of immune restoration given cART, particularly if BMI is >18.5kg/m(2) or they are female. These patients may benefit from increased monitoring and nutritional support during cART.
View details for DOI 10.1016/j.ijid.2015.04.008
View details for Web of Science ID 000358004000017
View details for PubMedID 25910854
View details for PubMedCentralID PMC4497838
The Epidemiology and Geographic Distribution of Nontuberculous Mycobacteria Clinical Isolates from Sputum Samples in the Eastern Region of China
PLOS NEGLECTED TROPICAL DISEASES
2015; 9 (3)
Nontuberculous mycobacteria (NTM) have been reported to be increasing worldwide and its geographic distribution differs by region. The aim of this study was to describe the epidemiology and distribution of NTM in the eastern part of China.Sputum samples were collected from 30 surveillance sites for tuberculosis drug resistance test from May 1, 2008 to December 31, 2008. Identification was performed using a biochemical test, multiplex PCR and GenoType Mycobacterium CM/AS assay.A total of 1779 smear positive clinical isolates were obtained, of which 60 (3.37%) were NTM. Five species/complex of NTM were identified; M. intracellulare was the predominated species (68.33%), followed by M. abscessus-M. immunogenum (13.33%), Mycobacterium spec. (10.00%), M. Kansasii (6.67%) and M. peregrinum-M. alvei-M. septicum (1.67%).M. intracellulare was the main species of NTM in the eastern part of China and clinical physicians should pay more attention to NTM induced pulmonary disease.
View details for DOI 10.1371/journal.pntd.0003623
View details for Web of Science ID 000352199400081
View details for PubMedID 25775117
View details for PubMedCentralID PMC4361326
Diagnostic Value of GeneChip for Detection of Resistant Mycobacterium tuberculosis in Patients with Differing Treatment Histories
JOURNAL OF CLINICAL MICROBIOLOGY
2015; 53 (1): 131-135
The increasing burden of drug-resistant tuberculosis (TB) poses an escalating threat to national TB control programs. To assist appropriate treatment for TB patients, accurate and rapid detection of drug resistance is critical. The GeneChip test is a novel molecular tool for the diagnosis of TB drug resistance. Performance-related data on GeneChip are limited, and evaluation in new and previously treated TB cases has never been performed. We evaluated the diagnostic performance of GeneChip in detecting resistance to rifampin (RMP) and isoniazid (INH) and in detecting multidrug-resistant tuberculosis (MDR-TB) in comparison with standard drug susceptibility testing (DST) and compared the results in a group of previously treated and newly detected TB patients in an urban area in southeastern China. One thousand one hundred seventy-three (83.8%) new cases and 227 (16.2%) previously treated cases were collected between January 2011 and September 2013. The GeneChip showed a specificity of 97.8% and a sensitivity of 94.8% for detection of RMP resistance and 97.3% and 70.9%, respectively, for INH resistance in new cases. For previously treated cases, the overall sensitivity, specificity, and agreement rate are 94.6%, 91.3%, and 92.1%, respectively, for detection of RMP resistance and 69.7%, 95.4%, and 86.8%, respectively, for INH resistance. The sensitivity and specificity of MDR-TB were 81.8% and 99.0% in new cases and 77.8% and 93.4% in previously treated cases, respectively. The GeneChip system provides a simple, rapid, reliable, and accurate clinical assay for the detection of TB drug resistance, and it is a potentially important diagnostic tool in a high-prevalence area.
View details for DOI 10.1128/JCM.02283-14
View details for Web of Science ID 000346502200021
View details for PubMedID 25355771
View details for PubMedCentralID PMC4290911
Changes in Tuberculin Skin Test Positivity Over 20 Years in Periurban Shantytowns in Lima, Peru
AMERICAN JOURNAL OF TROPICAL MEDICINE AND HYGIENE
2013; 89 (3): 507-515
A cross-sectional, community-based study was performed in 2012 with 428 residents of periurban shantytowns in Lima, Peru to study risk factors for and changes in latent tuberculosis infection in age-stratified groups compared with our data from the same region in 1990 (N = 219) and 2005 (N = 103). Tuberculin skin test positivity in these communities was highly prevalent at 52% overall, increased with age (P < 0.01) and was similar to 2005 (53%) and 1990 (48%). From 1990 to 2012, the prevalence of tuberculin positivity decreased in 5-14 and 15-24 year old groups (to 17% and 34%, respectively, both P < 0.05). However, this may be explained by cessation of Bacille Calmette-Guérin revaccination during this period, because Bacille Calmette-Guérin revaccination doubled tuberculin positivity. Over the same 22-year period, tuberculin positivity in the ≥ 25 year old group remained high (71%, P = 0.3), suggesting that prevalent latent tuberculosis infection persists in the adult population despite improving medical care and socioeconomic development in this region.
View details for DOI 10.4269/ajtmh.13-0005
View details for Web of Science ID 000326129900019
View details for PubMedID 23878185
View details for PubMedCentralID PMC3771290
Cutaneous Leishmaniasis "Chiclero's Ulcer" in Subtropical Ecuador
AMERICAN JOURNAL OF TROPICAL MEDICINE AND HYGIENE
2013; 89 (2): 195-196
An 18-year-old female presented with a severe ulcerative lesion on her right ear of 6 weeks duration. Her right ear was edematous and erythematous with a large, painless ulcerative lesion covering a third of the pinna and satellite papular lesions on the posterior. She was diagnosed with chiclero's ulcer. A skin smear stained with Diff-quik showed abundant Leishmania parasites. Chiclero's ulcer is a rare clinical presentation and is typically severe and difficult to treat. Physicians in Ecuador recommend administering prolonged intramuscular Glucantime. Side effects are common and can be severe resulting in low patient compliance. Because of preferences of the patient and the large volume needed for her weight, we recommended topical treatment with a lotion of Glucantime mixed half and half with white Merthiolate. After applying this lotion to the lesion 3 to 4 times a day for 6 weeks, the lesion healed.
View details for DOI 10.4269/ajtmh.12-0690
View details for Web of Science ID 000322683100001
View details for PubMedID 23926136
View details for PubMedCentralID PMC3741233
Free-ranging chickens in households in a periurban shantytown in Peru--attitudes and practices 10 years after a community-based intervention project.
The American journal of tropical medicine and hygiene
2013; 89 (2): 229-231
Free-ranging chickens are often found in periurban communities in developing countries, and their feces can pose a significant public health sanitation problem. Corralling chickens raised in these periurban areas in chicken coops has been proposed previously as an intervention to address this problem. Aims of this study were to revisit households in a corralling intervention study conducted in 2000-2001 to compare poultry-raising practices and investigate current attitudes regarding the impact of raising chickens in a periurban environment. Sociobehavioral questionnaires were given sequentially to all study participants; 30 families (58%) ceased raising poultry of any kind, whereas 42 (81%) do not raise chickens in their home. This finding indicates a significant reduction in poultry-raising in our study population since 2000-2001, possibly because of acculturation and/or change in socioeconomic status. However, attitudes about corral use for raising poultry were overwhelmingly positive, and the most common reason cited was cleanliness of the home.
View details for DOI 10.4269/ajtmh.12-0760
View details for PubMedID 23817335
View details for PubMedCentralID PMC3741241