title: Physical distance, genetic relationship, age, and leprosy classification are independent risk factors for leprosy in contacts of patients with leprosy.
abstract: BACKGROUND
  Close contacts of patients with leprosy have a higher risk of developing leprosy. Several risk factors have been identified, including genetic relationship and physical distance. Their independent contributions to the risk of developing leprosy, however, have never been sufficiently quantified.
  
  
  METHODS
  Logistic-regression analysis was performed on intake data from a prospective cohort study of 1037 patients newly diagnosed as having leprosy and their 21,870 contacts.
  
  
  RESULTS
  Higher age showed an increased risk, with a bimodal distribution. Contacts of patients with paucibacillary (PB) leprosy with 2-5 lesions (PB2-5) and those with multibacillary (MB) leprosy had a higher risk than did contacts of patients with single-lesion PB leprosy. The core household group had a higher risk than other contacts living under the same roof and next-door neighbors, who again had a higher risk than neighbors of neighbors. A close genetic relationship indicated an increased risk when blood-related children, parents, and siblings were pooled together.
  
  
  CONCLUSIONS
  Age of the contact, the disease classification of the index patient, and physical and genetic distance were independently associated with the risk of a contact acquiring leprosy. Contact surveys in leprosy should be not only focused on household contacts but also extended to neighbors and consanguineous relatives, especially when the patient has PB2-5 or MB leprosy.
authors.affiliation: Department of Public Health, Erasmus MC, University Medical Center Rotterdam, The Netherlands. f.moet@erasmusmc.nl
authors.forename: F Johannes
authors.initials: FJ
authors.lastname: Moet
authors.forename: David
authors.initials: D
authors.lastname: Pahan
authors.forename: Ron P
authors.initials: RP
authors.lastname: Schuring
authors.forename: Linda
authors.initials: L
authors.lastname: Oskam
authors.forename: Jan H
authors.initials: JH
authors.lastname: Richardus
mesh_terms: D000293:Adolescent; D000328:Adult; D017677:Age Distribution; D001459:Bangladesh; D002648:Child; D002675:Child, Preschool; D015331:Cohort Studies; D016358:Contact Tracing / Q000379:methods*; D005191:Family Characteristics; D005260:Female; D006801:Humans; D007918:Leprosy / Q000145:classification / Q000453:epidemiology / Q000235:genetics / Q000635:transmission; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D012307:Risk Factors; D017678:Sex Distribution