The epidemic potential of avian influenza A (H7N9) virus in humans in mainland China: A two-stage risk analysis

Abstract

Background: From 2013 to 2017, more than one thousand avian influenza A (H7N9) confirmed cases with hundreds of deaths were reported in mainland China. To identify priorities for epidemic prevention and control, a risk assessing framework for subnational variations is needed to define the epidemic potential of A (H7N9).

Methods: We established a consolidated two-stage framework that outlined the potential epidemic of H7N9 in humans: The Stage 1, index-case potential, used a Boosted Regression Trees model to assess population at risk due to spillover from poultry; the Stage 2, epidemic potential, synthesized the variables upon a framework of the Index for Risk Management to measure epidemic potential based on the probability of hazards and exposure, the vulnerability and coping capacity.

Results: Provinces in southern and eastern China, especially Jiangsu, Zhejiang, Guangzhou, have high index-case potential of human infected with A (H7N9), while northern coastal provinces and municipalities with low morbidity, i.e. Tianjin and Liaoning, have an increasing risk of A (H7N9) infection. Provinces in central China are likely to have high potential of epidemic due to the high vulnerability and the lack of coping capacity.

Conclusions: This study provides a unified risk assessment of A (H7N9) to detect the two-stage heterogeneity of epidemic potential among different provinces in mainland China, allowing proactively evaluate health preparedness at subnational levels to improve surveillance, diagnostic capabilities, and health promotion.

Fig 1. Graphical presentation of epidemic potential INFORM.

Note: the exposure to risk was the index-case potential of Stage 1.

Fig 2. Geographic distribution of A (H7N9) cases from 2012 to 2017.

Note: Data were unavailable in the grey regions in the map.

Fig 3. Index-case potential and epidemic potential based on INFORM.

Note: (A) Index-case potential standardized by INFORM methods. (B) Epidemic potential based on INFORM. Those coloured in red had high risk and in white had low risk. Data are unavailable in the grey regions in the map.