title: Recent TB transmission, clustering and predictors of large clusters in London, 2010-2012: results from first 3 years of universal MIRU-VNTR strain typing.
abstract: The incidence of TB has doubled in the last 20 years in London. A better understanding of risk groups for recent transmission is required to effectively target interventions. We investigated the molecular epidemiological characteristics of TB cases to estimate the proportion of cases due to recent transmission, and identify predictors for belonging to a cluster.
  
  
  
  The study population included all culture-positive TB cases in London residents, notified between January 2010 and December 2012, strain typed using 24-loci multiple interspersed repetitive units-variable number tandem repeats. Multivariable logistic regression analysis was performed to assess the risk factors for clustering using sociodemographic and clinical characteristics of cases and for cluster size based on the characteristics of the first two cases.
  
  
  
  There were 10 147 cases of which 5728 (57%) were culture confirmed and 4790 isolates (84%) were typed. 2194 (46%) were clustered in 570 clusters, and the estimated proportion attributable to recent transmission was 34%. Clustered cases were more likely to be UK born, have pulmonary TB, a previous diagnosis, a history of substance abuse or alcohol abuse and imprisonment, be of white, Indian, black-African or Caribbean ethnicity. The time between notification of the first two cases was more likely to be <90 days in large clusters.
  
  
  
  Up to a third of TB cases in London may be due to recent transmission. Resources should be directed to the timely investigation of clusters involving cases with risk factors, particularly those with a short period between the first two cases, to interrupt onward transmission of TB.
authors.affiliation: Field Epidemiology Services (Victoria), Public Health England, London, UK.
authors.forename: Esther L
authors.initials: EL
authors.lastname: Hamblion
authors.affiliation: Field Epidemiology Services (Victoria), Public Health England, London, UK European Programme for Intervention Epidemiology Training (EPIET), European Centre for Disease Control and Prevention, Stockholm, Sweden.
authors.forename: Arnaud
authors.initials: A
authors.lastname: Le Menach
authors.affiliation: Tuberculosis Section, Respiratory Disease Department, Public Health England, London, UK.
authors.forename: Laura F
authors.initials: LF
authors.lastname: Anderson
authors.affiliation: Tuberculosis Section, Respiratory Disease Department, Public Health England, London, UK.
authors.forename: Maeve K
authors.initials: MK
authors.lastname: Lalor
authors.affiliation: National Mycobacterium Reference Laboratory, Institute of Cell and Molecular Science (ICMS), London, UK.
authors.forename: Tim
authors.initials: T
authors.lastname: Brown
authors.affiliation: Tuberculosis Section, Respiratory Disease Department, Public Health England, London, UK Centre for Infectious Disease Epidemiology, University College London, Mortimer Market Centre, London, UK.
authors.forename: Ibrahim
authors.initials: I
authors.lastname: Abubakar
authors.affiliation: Field Epidemiology Services (Victoria), Public Health England, London, UK.
authors.forename: Charlotte
authors.initials: C
authors.lastname: Anderson
authors.affiliation: Field Epidemiology Services (Victoria), Public Health England, London, UK European Programme for Intervention Epidemiology Training (EPIET), European Centre for Disease Control and Prevention, Stockholm, Sweden.
authors.forename: Helen
authors.initials: H
authors.lastname: Maguire
authors.affiliation: Field Epidemiology Services (Victoria), Public Health England, London, UK.
authors.forename: Sarah R
authors.initials: SR
authors.lastname: Anderson
mesh_terms: D000328:Adult; D016000:Cluster Analysis; D005260:Female; D005838:Genotype; D006801:Humans; D015994:Incidence; D008131:London / Q000453:epidemiology; D008297:Male; D009169:Mycobacterium tuberculosis / Q000302:isolation & purification; D011237:Predictive Value of Tests; D012189:Retrospective Studies; D012307:Risk Factors; D012680:Sensitivity and Specificity; D014397:Tuberculosis, Pulmonary / Q000175:diagnosis / Q000453:epidemiology / Q000382:microbiology / Q000635:transmission*
keywords: Clinical Epidemiology; Tuberculosis