Estimating the between-farm transmission rates for highly pathogenic avian influenza subtype H5N1 epidemics in Bangladesh between 2007 and 2013

A. Ssematimba, I. Okike, G.M. Ahmed, M. Yamage, G.J. Boender, T.J. Hagenaars, B. Bett

Research output: Contribution to journalArticleAcademicpeer-review

4 Citations (Scopus)

Abstract

Highly Pathogenic Avian Influenza (HPAI) is classified by the World Organization for Animal Health as one of the notifiable diseases. Its occurrence is associated with severe socio-economic impacts and is also zoonotic. Bangladesh HPAI epidemic data for the period between 2007 and 2013 were obtained and split into epidemic waves based on the time lag between outbreaks. By assuming the number of newly infected farms to be binomially distributed, we fit a Generalized Linear Model to the data to estimate between-farm transmission rates (β). These parameters are then used together with the calculated infectious periods to estimate the respective basic reproduction numbers (R0). The change in β and R0 with time during the course of each epidemic wave was explored. Finally, sensitivity analyses of the effects of reducing the delay in detecting infection on a farm as well as extended infectiousness of a farm beyond the day of culling were assessed. The point estimates obtained for β ranged from 0.08 (95% CI: 0.06–0.10) to 0.11 (95% CI: 0.08–0.20) per infectious farm per day while R0 ranged from 0.85 (95% CI: 0.77–1.02) to 0.96 (95% CI: 0.72–1.20). Sensitivity analyses reveal that the estimates are quite robust to changes in the assumptions about the day in reporting infection and extended infectiousness. In the analysis allowing for time-varying transmission parameters, the rising and declining phases observed in the epidemic data were synchronized with the moments when R0 was greater and less than one, respectively. From an epidemiological perspective, the consistency of these estimates and their magnitude (R0 ≈ 1) indicate that the effectiveness of the deployed control measures was largely invariant between epidemic waves and the trend of the time-varying R0 supports the hypothesis of sustained farm-to-farm transmission that is possibly initiated by a few unique introductions.
LanguageEnglish
Pagese127-e134
JournalTransboundary and Emerging Diseases
Volume65
Issue number1
DOIs
Publication statusPublished - 1 Feb 2018

Fingerprint

Influenza in Birds
Bangladesh
avian influenza
farms
Basic Reproduction Number
notifiable disease
Zoonoses
economic impact
Infection
Farms
animal health
infection
Disease Outbreaks
socioeconomics
control methods
Linear Models
linear models
Economics

Keywords

  • disease control
  • transmission
  • veterinary epidemiology
  • zoonosis/zoonotics

Cite this

@article{66db56c4da4b466881811965233a9fd0,
title = "Estimating the between-farm transmission rates for highly pathogenic avian influenza subtype H5N1 epidemics in Bangladesh between 2007 and 2013",
abstract = "Highly Pathogenic Avian Influenza (HPAI) is classified by the World Organization for Animal Health as one of the notifiable diseases. Its occurrence is associated with severe socio-economic impacts and is also zoonotic. Bangladesh HPAI epidemic data for the period between 2007 and 2013 were obtained and split into epidemic waves based on the time lag between outbreaks. By assuming the number of newly infected farms to be binomially distributed, we fit a Generalized Linear Model to the data to estimate between-farm transmission rates (β). These parameters are then used together with the calculated infectious periods to estimate the respective basic reproduction numbers (R0). The change in β and R0 with time during the course of each epidemic wave was explored. Finally, sensitivity analyses of the effects of reducing the delay in detecting infection on a farm as well as extended infectiousness of a farm beyond the day of culling were assessed. The point estimates obtained for β ranged from 0.08 (95{\%} CI: 0.06–0.10) to 0.11 (95{\%} CI: 0.08–0.20) per infectious farm per day while R0 ranged from 0.85 (95{\%} CI: 0.77–1.02) to 0.96 (95{\%} CI: 0.72–1.20). Sensitivity analyses reveal that the estimates are quite robust to changes in the assumptions about the day in reporting infection and extended infectiousness. In the analysis allowing for time-varying transmission parameters, the rising and declining phases observed in the epidemic data were synchronized with the moments when R0 was greater and less than one, respectively. From an epidemiological perspective, the consistency of these estimates and their magnitude (R0 ≈ 1) indicate that the effectiveness of the deployed control measures was largely invariant between epidemic waves and the trend of the time-varying R0 supports the hypothesis of sustained farm-to-farm transmission that is possibly initiated by a few unique introductions.",
keywords = "disease control, transmission, veterinary epidemiology, zoonosis/zoonotics",
author = "A. Ssematimba and I. Okike and G.M. Ahmed and M. Yamage and G.J. Boender and T.J. Hagenaars and B. Bett",
year = "2018",
month = "2",
day = "1",
doi = "10.1111/tbed.12692",
language = "English",
volume = "65",
pages = "e127--e134",
journal = "Transboundary and Emerging Diseases",
issn = "1865-1674",
publisher = "Wiley",
number = "1",

}

Estimating the between-farm transmission rates for highly pathogenic avian influenza subtype H5N1 epidemics in Bangladesh between 2007 and 2013. / Ssematimba, A.; Okike, I.; Ahmed, G.M.; Yamage, M.; Boender, G.J.; Hagenaars, T.J.; Bett, B.

In: Transboundary and Emerging Diseases, Vol. 65, No. 1, 01.02.2018, p. e127-e134.

Research output: Contribution to journalArticleAcademicpeer-review

TY - JOUR

T1 - Estimating the between-farm transmission rates for highly pathogenic avian influenza subtype H5N1 epidemics in Bangladesh between 2007 and 2013

AU - Ssematimba, A.

AU - Okike, I.

AU - Ahmed, G.M.

AU - Yamage, M.

AU - Boender, G.J.

AU - Hagenaars, T.J.

AU - Bett, B.

PY - 2018/2/1

Y1 - 2018/2/1

N2 - Highly Pathogenic Avian Influenza (HPAI) is classified by the World Organization for Animal Health as one of the notifiable diseases. Its occurrence is associated with severe socio-economic impacts and is also zoonotic. Bangladesh HPAI epidemic data for the period between 2007 and 2013 were obtained and split into epidemic waves based on the time lag between outbreaks. By assuming the number of newly infected farms to be binomially distributed, we fit a Generalized Linear Model to the data to estimate between-farm transmission rates (β). These parameters are then used together with the calculated infectious periods to estimate the respective basic reproduction numbers (R0). The change in β and R0 with time during the course of each epidemic wave was explored. Finally, sensitivity analyses of the effects of reducing the delay in detecting infection on a farm as well as extended infectiousness of a farm beyond the day of culling were assessed. The point estimates obtained for β ranged from 0.08 (95% CI: 0.06–0.10) to 0.11 (95% CI: 0.08–0.20) per infectious farm per day while R0 ranged from 0.85 (95% CI: 0.77–1.02) to 0.96 (95% CI: 0.72–1.20). Sensitivity analyses reveal that the estimates are quite robust to changes in the assumptions about the day in reporting infection and extended infectiousness. In the analysis allowing for time-varying transmission parameters, the rising and declining phases observed in the epidemic data were synchronized with the moments when R0 was greater and less than one, respectively. From an epidemiological perspective, the consistency of these estimates and their magnitude (R0 ≈ 1) indicate that the effectiveness of the deployed control measures was largely invariant between epidemic waves and the trend of the time-varying R0 supports the hypothesis of sustained farm-to-farm transmission that is possibly initiated by a few unique introductions.

AB - Highly Pathogenic Avian Influenza (HPAI) is classified by the World Organization for Animal Health as one of the notifiable diseases. Its occurrence is associated with severe socio-economic impacts and is also zoonotic. Bangladesh HPAI epidemic data for the period between 2007 and 2013 were obtained and split into epidemic waves based on the time lag between outbreaks. By assuming the number of newly infected farms to be binomially distributed, we fit a Generalized Linear Model to the data to estimate between-farm transmission rates (β). These parameters are then used together with the calculated infectious periods to estimate the respective basic reproduction numbers (R0). The change in β and R0 with time during the course of each epidemic wave was explored. Finally, sensitivity analyses of the effects of reducing the delay in detecting infection on a farm as well as extended infectiousness of a farm beyond the day of culling were assessed. The point estimates obtained for β ranged from 0.08 (95% CI: 0.06–0.10) to 0.11 (95% CI: 0.08–0.20) per infectious farm per day while R0 ranged from 0.85 (95% CI: 0.77–1.02) to 0.96 (95% CI: 0.72–1.20). Sensitivity analyses reveal that the estimates are quite robust to changes in the assumptions about the day in reporting infection and extended infectiousness. In the analysis allowing for time-varying transmission parameters, the rising and declining phases observed in the epidemic data were synchronized with the moments when R0 was greater and less than one, respectively. From an epidemiological perspective, the consistency of these estimates and their magnitude (R0 ≈ 1) indicate that the effectiveness of the deployed control measures was largely invariant between epidemic waves and the trend of the time-varying R0 supports the hypothesis of sustained farm-to-farm transmission that is possibly initiated by a few unique introductions.

KW - disease control

KW - transmission

KW - veterinary epidemiology

KW - zoonosis/zoonotics

U2 - 10.1111/tbed.12692

DO - 10.1111/tbed.12692

M3 - Article

VL - 65

SP - e127-e134

JO - Transboundary and Emerging Diseases

T2 - Transboundary and Emerging Diseases

JF - Transboundary and Emerging Diseases

SN - 1865-1674

IS - 1

ER -