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Quantification of bird-to-bird and bird-to-human infections during 2013 novel H7N9 avian influenza outbreak in China.

Hsieh YH, Wu J, Fang J, Yang Y, Lou J - PLoS ONE (2014)

Bottom Line: From February to May, 2013, 132 human avian influenza H7N9 cases were identified in China resulting in 37 deaths.Moreover, the turning point of the human epidemic, pinpointed at shortly after the implementation of full-scale control and intervention measures initiated in early April, further highlights the impact of timely actions on ending the outbreak.This is the first study where both the bird and human components of an avian influenza epidemic can be quantified using only the human case data.

View Article: PubMed Central - PubMed

Affiliation: Department of Public Health, China Medical University, Taichung, Taiwan; Center for Infectious Disease Education and Research, China Medical University, Taichung, Taiwan.

ABSTRACT
From February to May, 2013, 132 human avian influenza H7N9 cases were identified in China resulting in 37 deaths. We developed a novel, simple and effective compartmental modeling framework for transmissions among (wild and domestic) birds as well as from birds to human, to infer important epidemiological quantifiers, such as basic reproduction number for bird epidemic, bird-to-human infection rate and turning points of the epidemics, for the epidemic via human H7N9 case onset data and to acquire useful information regarding the bird-to-human transmission dynamics. Estimated basic reproduction number for infections among birds is 4.10 and the mean daily number of human infections per infected bird is 3.16*10-5 [3.08*10-5, 3.23*10-5]. The turning point of 2013 H7N9 epidemic is pinpointed at April 16 for bird infections and at April 9 for bird-to-human transmissions. Our result reveals very low level of bird-to-human infections, thus indicating minimal risk of widespread bird-to-human infections of H7N9 virus during the outbreak. Moreover, the turning point of the human epidemic, pinpointed at shortly after the implementation of full-scale control and intervention measures initiated in early April, further highlights the impact of timely actions on ending the outbreak. This is the first study where both the bird and human components of an avian influenza epidemic can be quantified using only the human case data.

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Model diagram for bird-human disease transmission model.
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pone-0111834-g001: Model diagram for bird-human disease transmission model.

Mentions: The human population susceptible to the H7N9 virus is assumed to remain at a constant level during the early stage of outbreak. Moreover, there is no evidence indicating that either human-to-human or human-to-bird infection had occurred. Thus, the cumulative number of human H7N9 cases by infected birds, IH, can be simply modeled (see Mathematical Details section) so the increase rate of the infected human individuals is proportional to the number of the infected birds, with the proportionality constant ()-the daily human infection rate per infected bird. Integration of this simple model establishes a link between the cumulative number of H7N9-infected humans and the total number of birds. See Mathematical Details section for more details. For illustration, the bird-human model diagram is provided in Figure 1.


Quantification of bird-to-bird and bird-to-human infections during 2013 novel H7N9 avian influenza outbreak in China.

Hsieh YH, Wu J, Fang J, Yang Y, Lou J - PLoS ONE (2014)

Model diagram for bird-human disease transmission model.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4257544&req=5

pone-0111834-g001: Model diagram for bird-human disease transmission model.
Mentions: The human population susceptible to the H7N9 virus is assumed to remain at a constant level during the early stage of outbreak. Moreover, there is no evidence indicating that either human-to-human or human-to-bird infection had occurred. Thus, the cumulative number of human H7N9 cases by infected birds, IH, can be simply modeled (see Mathematical Details section) so the increase rate of the infected human individuals is proportional to the number of the infected birds, with the proportionality constant ()-the daily human infection rate per infected bird. Integration of this simple model establishes a link between the cumulative number of H7N9-infected humans and the total number of birds. See Mathematical Details section for more details. For illustration, the bird-human model diagram is provided in Figure 1.

Bottom Line: From February to May, 2013, 132 human avian influenza H7N9 cases were identified in China resulting in 37 deaths.Moreover, the turning point of the human epidemic, pinpointed at shortly after the implementation of full-scale control and intervention measures initiated in early April, further highlights the impact of timely actions on ending the outbreak.This is the first study where both the bird and human components of an avian influenza epidemic can be quantified using only the human case data.

View Article: PubMed Central - PubMed

Affiliation: Department of Public Health, China Medical University, Taichung, Taiwan; Center for Infectious Disease Education and Research, China Medical University, Taichung, Taiwan.

ABSTRACT
From February to May, 2013, 132 human avian influenza H7N9 cases were identified in China resulting in 37 deaths. We developed a novel, simple and effective compartmental modeling framework for transmissions among (wild and domestic) birds as well as from birds to human, to infer important epidemiological quantifiers, such as basic reproduction number for bird epidemic, bird-to-human infection rate and turning points of the epidemics, for the epidemic via human H7N9 case onset data and to acquire useful information regarding the bird-to-human transmission dynamics. Estimated basic reproduction number for infections among birds is 4.10 and the mean daily number of human infections per infected bird is 3.16*10-5 [3.08*10-5, 3.23*10-5]. The turning point of 2013 H7N9 epidemic is pinpointed at April 16 for bird infections and at April 9 for bird-to-human transmissions. Our result reveals very low level of bird-to-human infections, thus indicating minimal risk of widespread bird-to-human infections of H7N9 virus during the outbreak. Moreover, the turning point of the human epidemic, pinpointed at shortly after the implementation of full-scale control and intervention measures initiated in early April, further highlights the impact of timely actions on ending the outbreak. This is the first study where both the bird and human components of an avian influenza epidemic can be quantified using only the human case data.

Show MeSH
Related in: MedlinePlus