Dataset Information

Transmissibility of tuberculosis among school contacts: an outbreak investigation in a boarding middle school, China.

ABSTRACT: Tuberculosis (TB) outbreak occurred in a boarding middle school of China. We explored its probable sources and quantified the transmissibility and pathogenicity of TB. Clinical evaluation, tuberculin skin testing and chest radiography were conducted to identify TB cases. Mycobacterium tuberculosis isolates underwent genotyping analysis to identify the outbreak source. A chain-binomial transmission model was used to evaluate transmissibility and pathogenicity of TB. A total of 46 active cases were ascertained among 258 students and 15 teachers/staff, an attack rate of 16.8%. Genetic analyses revealed two groups of M. tuberculosis cocirculating during the outbreak and possible importation from local communities. Secondary attack rates among students were 4.1% (2.9%, 5.3%) within grade and 7.9% (4.9%, 11%) within class. An active TB case was estimated to infect 8.4 (7.2, 9.6) susceptible people on average. The smear-positive cases were 28 (8, 101) times as infective as smear-negative cases. Previous BCG vaccination could reduce the probability of developing symptoms after infection by 70% (1.4%, 91%). The integration of clinical evaluation, genetic sequencing, and statistical modeling greatly enhanced our understanding of TB transmission dynamics. Timely diagnosis of smear-positive cases, especially in the early phase of the outbreak, is the key to preventing further spread among close contacts.

SUBMITTER: Ma MJ

PROVIDER: S-EPMC4427569 | biostudies-literature | 2015 Jun

REPOSITORIES: biostudies-literature

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Transmissibility of tuberculosis among school contacts: an outbreak investigation in a boarding middle school, China.

Ma Mai-Juan MJ Yang Yang Y Wang Hai-Bin HB Zhu Yi-Fan YF Fang Li-Qun LQ An Xiao-Ping XP Wan Kang-Lin KL Whalen Christopher C CC Yang Xiao-Xian XX Lauzardo Michael M Zhang Zhi-Yi ZY Cao Jin-Feng JF Tong Yi-Gang YG Dai Er-Hei EH Cao Wu-Chun WC

Infection, genetics and evolution : journal of molecular epidemiology and evolutionary genetics in infectious diseases 20150307

Tuberculosis (TB) outbreak occurred in a boarding middle school of China. We explored its probable sources and quantified the transmissibility and pathogenicity of TB. Clinical evaluation, tuberculin skin testing and chest radiography were conducted to identify TB cases. Mycobacterium tuberculosis isolates underwent genotyping analysis to identify the outbreak source. A chain-binomial transmission model was used to evaluate transmissibility and pathogenicity of TB. A total of 46 active cases wer ...[more]

PMID: 25757905

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Project description:BACKGROUND:In 2013, a tuberculosis (TB) outbreak occurred in a middle school in Henan province of China. An outbreak survey was carried out in the school. OBJECTIVES:This study was undertaken to investigate the detection rate of TB cases and those with strong Mantoux positive (SMP), defined as tuberculin skin test (TST) indurations of 15mm or larger and/or blisters, necrosis or lymphangitis, and to identify their risk factors. METHODS:The TST, chest x-ray/radiography, and TB-suspicious symptoms interview were used to screen for TB cases. Their diagnosis was made by sputum smear microscopy, liquid culture, computed tomography (CT), and diagnostic therapy if necessary. We retrospectively analyzed the outbreak survey data of 4082 students and 278 staff in the school. Logistic regression models were used to identify the risk factors associated with SMP and TB disease. RESULTS:Approximately 3.55% of students and 16.55% of staff were SMP. SMP rate in students was significantly lower than that in staff (p<0.001). 55 TB cases in students and none in staff were identified in the school from February to November, 2013, with a detection rate of 1.35% for students. SMP and TB case detection rates were 20.29% and 41.77%, respectively, in the index class, both significantly higher than that in the other classes (3.26% and 0.55%, respectively; both p<0.001). In the index class, TB case detection rate over the study period in students with SMP was not significantly higher than that with TST indurations of <15mm (38.18% vs 21.43%, p = 0.24), but it was significantly higher in the other classes (7.81% vs 0.18%, p<0.001). Risk factors independently associated with SMP and TB cases shared the following with the index case: same dormitory-floor (adjusted odds ratio (AOR) 5.36, 95% CI 3.02-9.48, p<0.001 for SMP; AOR 2.67; 95% CI 1.03-6.96, p = 0.044 for TB cases), same classroom (AOR 4.01; 95% CI 1.95-8.26, p<0.001 for SMP; AOR 165.08; 95% CI 66.88-407.47, p<0.001 for TB cases), same teaching-floor in different classroom (AOR 5.41; 95% CI 3.02-9.71, p<0.001 for SMP; AOR 11.24; 95% CI 3.71-34.03, p<0.001 for TB cases) and same teaching-building on different floor (AOR 1.81; 95% CI 1.16-2.85, p = 0.009 for SMP; AOR 3.30; 95% CI 1.16-9.42, p = 0.025 for TB cases). The closer the contact was with the index case, the larger the AORs for SMP and TB cases were. CONCLUSION:Same dormitory-floor, same classroom, same teaching-floor and same teaching-building with the index case were all risk factors for both TB infection and disease for students in the outbreak, and the closer the contact was with the index case, the higher the risk was observed. Attention should also be paid to students with TST indurations <15mm, as well as to those with that ?15mm for the index class in dealing with the outbreak.

Project description:BackgroundIn October 2016, a senior high school student was diagnosed with sputum-smear positive [SS(+)] pulmonary tuberculosis (TB). We conducted an investigation of an outbreak in the school, including among students and teachers diagnosed with latent TB, who we followed until July 2019.MethodsWe defined latent TB infection (LTBI) as a tuberculin skin test (TST) induration of 15mm or larger; probable TB as a chest radiograph indicative of TB plus productive cough/hemoptysis for at least 2 weeks, or TST induration of 15mm or larger; and confirmed TB as two or more positive sputum smears or one positive sputum smear plus a chest radiograph indicative of TB or culture positive with M. tuberculosis. We conducted mycobacterial interspersed repetitive unit-variable number tandem repeat (MIRU-VNTR) typing based on 24 loci in the isolates.ResultsBetween October 2016 and July 2019, we identified 52 cases, including nine probable, six confirmed, and 37 LTBI cases. The index case-student had attended school continuously despite having TB symptoms for almost three months before being diagnosed with TB. We obtained three isolates from classmates of the index case in 2016; all had identical MIRU-VNTR alleles with the index case. The LTBI rate was lower among students (7.41%, 30/405) than among teachers (26.92%, 7/26) (rate ratio [RR] = 0.28, 95% confidential interval [CI]: 0.13-0.57). Among the 17 students who had latent TB and refused prophylaxis in October 2016, 23.53% (4/17) became probable/confirmed cases by July 2019. None of the six teachers who also refused prophylaxis became probable or confirmed cases. Of the 176 students who were TST(-) in October 2016, 1.70% (3/176) became probable/confirmed cases, and among the 20 teachers who were TST(-), 1 became a probable case.ConclusionsDelayed diagnosis of TB in the index patient may have contributed to the start of this outbreak; lack of post-exposure chemoprophylaxis facilitated spread of the outbreak. Post-exposure prophylaxis is strongly recommended for all TST-positive students; TST-negative students exposed to an SS(+) case should be followed up regularly so that prophylaxis can be started if LTBI is detected.

Project description:Tuberculosis (TB) risk is highest immediately after primary infection, and young children are vulnerable to rapid and severe TB disease. Contact tracing should identify infected children rapidly and simultaneously target resources effectively. We conducted a retrospective review of the paediatric TB contact tracing results in the Hospital District of Helsinki and Uusimaa from 2012 to 2016 and identified risk factors for TB disease or infection. Altogether, 121 index cases had 526 paediatric contacts of whom 34 were diagnosed with TB disease or infection. The maximum delay until first contact investigation visit among the household contacts under 5 years of age with either TB disease or infection was 7 days. The yield for TB disease or infection was 4.6% and 12.8% for household contacts, 0.5% and 0% for contacts exposed in a congregate setting and 1.4% and 5.0% for other contacts, respectively. Contacts born in a TB endemic country (aOR 3.07, 95% CI 1.10-8.57), with household exposure (aOR 2.96, 95% CI 1.33-6.58) or a sputum smear positive index case (aOR 3.96, 95% CI 1.20-13.03) were more likely to have TB disease or infection.Conclusions: Prompt TB investigations and early diagnosis can be achieved with a well-organised contact tracing structure. The risk for TB infection or disease was higher among contacts with household exposure, a sputum smear positive index case or born in a TB endemic country. Large-scale investigations among children exposed in congregate settings can result in a very low yield and should be cautiously targeted. What is Known: • Vulnerable young children are a high priority in contact tracing and should be evaluated as soon as possible after TB exposure What is New: • Prompt investigations for paediatric TB contacts and early diagnosis of infected children can be achieved with a well-organised contact tracing structure • Large-scale investigations among children exposed in congregate settings can result in a very low yield and should be cautiously targeted.

Dataset Information

Transmissibility of tuberculosis among school contacts: an outbreak investigation in a boarding middle school, China.

Publications

Transmissibility of tuberculosis among school contacts: an outbreak investigation in a boarding middle school, China.

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