Although the source and mode of transmission of the novel influenza A (H7N9) virus infection in Mainland China have not yet been confirmed, a research team comprising scholars from Hong Kong and the Mainland recently developed an epidemiological diffusion model to assess the risks of H7N9 infection in Mainland China.  

The team, led by Professor Liu Jiming, Chair Professor of Computer Science of HKBU, also includes Dr. Shi Benyun, Research Assistant Professor and Mr. Xia Shang, PhD student of Computer Science of HKBU; Dr. Yang Guojing, Assistant Professor of the Jockey Club School of Public Health and Primary Care of The Chinese University of Hong Kong; and Professor Zhou Xiaonong of the Chinese Centre for Disease Control and Prevention. The team developed a map based on the northwards migratory patterns of birds using environmental and meteorological data over the same 12 weeks. With reference to the epidemiological diffusion model, the map spatiotemporally quantified the geographic spread of H7N9 infection. The findings provide insights into assessing the risks of H7N9 infection in eastern as well as other parts of Mainland China and guidance on ways to moderate its outbreak in the region.  

The team published a paper entitled “Inferring the potential risks of H7N9 infection by spatiotemporally characterizing bird migration and poultry distribution in eastern China” in the academic journal Infectious Diseases of Poverty on 3 May 2013. For details please visit: http://www.idpjournal.com/content/2/1/8/abstract.  

Since the first confirmed H7N9 infection case was announced, the team developed a method for estimating the likelihood of bird migration based on available environmental and meteorological data of eastern China for 12 weeks (4 February to 28 April 2013), from Zhejiang, Shanghai and Jiangsu, to Liaoning, Jilin and Heilongjiang. The possibility of migrant birds moving over these provinces was estimated and hence its impact on the potential spatiotemporal spread of H7N9 infection.  

Based on the poultry production and consumption in 31 provinces/municipalities in the Mainland, the team estimated the probability of distributing potentially infected poultry from one province/municipality to another. Although the majority of early cases of H7N9 were found in Shanghai, that city is not a major poultry exporter based on the model and the results also showed limited transmission via this route. In contrast, Jiangsu distributes poultry to Shanghai, Zhejiang and beyond. Transmission via this route poses greater risks of the spread of H7N9 infection.  

Considering the integrated infection risk of the above two transmission routes (bird migration and poultry distribution), the team developed a map displaying the estimated spatiotemporal patterns of the integrated risk caused by both bird migration and poultry distribution in eastern China (Enclosure 1). The map showed that during the first eight weeks, except for Jiangsu, Shanghai and Zhejiang, other provinces such as Hebei, Anhui, Shangdong and Beijing also had the risk of an outbreak of H7N9 infection. From week 8 until week 12, sustained infection risks in Hebei, Tianjin and Beijing can be observed.  

The preliminary mapping results provide insights on estimating the relative risks of influenza A (H7N9) virus within a certain period of time at a designated place. The model also explains the pattern of the most recent cases of H7N9 infection, providing effective tools for public health policymakers to perform active surveillance and control of H7N9 infections. In other words, given the lack of information on virus transmission, the results demonstrated in the mapping suggest that active surveillance of significant migrant birds areas and intensive intervention in poultry markets would contribute to effective control of the spread of the virus.  

The team is now exploring ways to adopt the computational model in the surveillance and control of diseases in more complicated environments. Team leader Professor Liu Jiming said: “At the present time, we do not have sufficient information to comprehend the source of H7N9 transmission, and human infection may depend on many other issues apart from those we mentioned. The diffusion model helped estimate the potential infection risks. By extending the model we will be able to predict future infection risk across central and western China. The results may contribute positively to other research areas of our team, namely malaria transmission, prevention and surveillance.”  

Professor Zhou Xiaonong added: “We will continue to work on research into the sources of infection of H7N9 and the mode of transmission. So far there is no evidence of sustained human-to-human transmission required for a pandemic to occur.”  

Enclosure 1: A map displaying the estimated spatiotemporal patterns of the integrated risk caused by both bird migration and poultry distribution in eastern China from 4 February to 28 April 2013.