title: Avian influenza H5N1 transmission in households, Indonesia.
abstract: BACKGROUND
  Disease transmission patterns are needed to inform public health interventions, but remain largely unknown for avian influenza H5N1 virus infections. A recent study on the 139 outbreaks detected in Indonesia between 2005 and 2009 found that the type of exposure to sources of H5N1 virus for both the index case and their household members impacted the risk of additional cases in the household. This study describes the disease transmission patterns in those outbreak households.
  
  
  RESULTS
  We compared cases (n = 177) and contacts (n = 496) in the 113 sporadic and 26 cluster outbreaks detected between July 2005 and July 2009 to estimate attack rates and disease intervals. We used final size household models to fit transmission parameters to data on household size, cases and blood-related household contacts to assess the relative contribution of zoonotic and human-to-human transmission of the virus, as well as the reproduction number for human virus transmission. The overall household attack rate was 18.3% and secondary attack rate was 5.5%. Secondary attack rate remained stable as household size increased. The mean interval between onset of subsequent cases in outbreaks was 5.6 days. The transmission model found that human transmission was very rare, with a reproduction number between 0.1 and 0.25, and the upper confidence bounds below 0.4. Transmission model fit was best when the denominator population was restricted to blood-related household contacts of index cases.
  
  
  CONCLUSIONS
  The study only found strong support for human transmission of the virus when a single large cluster was included in the transmission model. The reproduction number was well below the threshold for sustained transmission. This study provides baseline information on the transmission dynamics for the current zoonotic virus and can be used to detect and define signatures of a virus with increasing capacity for human-to-human transmission.
authors.affiliation: Directorate-General Disease Control and Environmental Health, Ministry of Health, Salemba, Jakarta, Indonesia.
authors.forename: Tjandra Y
authors.initials: TY
authors.lastname: Aditama
authors.forename: Gina
authors.initials: G
authors.lastname: Samaan
authors.forename: Rita
authors.initials: R
authors.lastname: Kusriastuti
authors.forename: Ondri Dwi
authors.initials: OD
authors.lastname: Sampurno
authors.forename: Wilfried
authors.initials: W
authors.lastname: Purba
authors.lastname: Misriyah
authors.forename: Hari
authors.initials: H
authors.lastname: Santoso
authors.forename: Arie
authors.initials: A
authors.lastname: Bratasena
authors.forename: Anas
authors.initials: A
authors.lastname: Maruf
authors.forename: Elvieda
authors.initials: E
authors.lastname: Sariwati
authors.forename: Vivi
authors.initials: V
authors.lastname: Setiawaty
authors.forename: Kathryn
authors.initials: K
authors.lastname: Glass
authors.forename: Kamalini
authors.initials: K
authors.lastname: Lokuge
authors.forename: Paul M
authors.initials: PM
authors.lastname: Kelly
authors.forename: I Nyoman
authors.initials: IN
authors.lastname: Kandun
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000818:Animals; D001717:Birds / Q000821:virology; D002648:Child; D002675:Child, Preschool; D016000:Cluster Analysis; D004196:Disease Outbreaks; D005191:Family Characteristics; D005260:Female; D006801:Humans; D007214:Indonesia / Q000453:epidemiology; D007223:Infant; D007231:Infant, Newborn; D053124:Influenza A Virus, H5N1 Subtype / Q000502:physiology; D005585:Influenza in Birds / Q000453:epidemiology / Q000635:transmission*; D007251:Influenza, Human / Q000453:epidemiology*; D008297:Male; D008875:Middle Aged; D009976:Orthomyxoviridae Infections / Q000453:epidemiology / Q000635:transmission*; D011201:Poultry Diseases / Q000453:epidemiology / Q000635:transmission / Q000821:virology; D055815:Young Adult; D015047:Zoonoses / Q000453:epidemiology / Q000635:transmission