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Shi B.,Hong Kong Baptist University | Liu J.,Hong Kong Baptist University | Zhou X.-N.,National Institute of Parasitic Diseases | Zhou X.-N.,Key Laboratory of Parasite and Vector Biology | And 2 more authors.
PLoS Neglected Tropical Diseases | Year: 2014

Background:The transmission networks of Plasmodium vivax characterize how the parasite transmits from one location to another, which are informative and insightful for public health policy makers to accurately predict the patterns of its geographical spread. However, such networks are not apparent from surveillance data because P. vivax transmission can be affected by many factors, such as the biological characteristics of mosquitoes and the mobility of human beings. Here, we pay special attention to the problem of how to infer the underlying transmission networks of P. vivax based on available tempo-spatial patterns of reported cases.Methodology:We first define a spatial transmission model, which involves representing both the heterogeneous transmission potential of P. vivax at individual locations and the mobility of infected populations among different locations. Based on the proposed transmission model, we further introduce a recurrent neural network model to infer the transmission networks from surveillance data. Specifically, in this model, we take into account multiple real-world factors, including the length of P. vivax incubation period, the impact of malaria control at different locations, and the total number of imported cases.Principal Findings:We implement our proposed models by focusing on the P. vivax transmission among 62 towns in Yunnan province, People's Republic China, which have been experiencing high malaria transmission in the past years. By conducting scenario analysis with respect to different numbers of imported cases, we can (i) infer the underlying P. vivax transmission networks, (ii) estimate the number of imported cases for each individual town, and (iii) quantify the roles of individual towns in the geographical spread of P. vivax.Conclusion:The demonstrated models have presented a general means for inferring the underlying transmission networks from surveillance data. The inferred networks will offer new insights into how to improve the predictability of P. vivax transmission. © 2014 Shi et al.


Shi B.,Hong Kong Baptist University | Xia S.,Hong Kong Baptist University | Yang G.-J.,Chinese University of Hong Kong | Zhou X.-N.,National Institute of Parasitic Diseases | And 3 more authors.
Infectious Diseases of Poverty | Year: 2013

Background: In view of the rapid geographic spread and the increasing number of confirmed cases of novel influenza A(H7N9) virus infections in eastern China, we developed a diffusion model to spatiotemporally characterize the impacts of bird migration and poultry distribution on the geographic spread of H7N9 infection. Methods: Three types of infection risks were estimated for 12 weeks, from February 4 to April 28, 2013, including (i) the risk caused by bird migration, (ii) the risk caused by poultry distribution, and (iii) the integrated risk caused by both bird migration and poultry distribution. To achieve this, we first developed a method for estimating the likelihood of bird migration based on available environmental and meteorological data. Then, we adopted a computational mobility model to estimate poultry distribution based on annual poultry production and consumption of each province/municipality. Finally, the spatiotemporal risk maps were created based on the integrated impacts of both bird migration and poultry distribution. Results: In the study of risk estimation caused by bird migration, the likelihood matrix was estimated based on the 7-day temperature, from February 4 to April 28, 2013. It was found the estimated migrant birds mainly appear in the southeastern provinces of Zhejiang, Shanghai and Jiangsu during Weeks 1 to 4, and Week 6, followed by appearing in central eastern provinces of Shandong, Hebei, Beijing, and Tianjin during Weeks 7 to 9, and finally in northeastern provinces of Liaoning, Jilin, and Heilongjiang during Weeks 10 to 12.In the study of risk caused by poultry distribution, poultry distribution matrix was created to show the probability of poultry distribution. In spite of the fact that the majority of the initial infections were reported in Shanghai and Jiangsu, the relative risk of H7N9 infection estimated based on the poultry distribution model predicted that Jiangsu may have a slightly higher likelihood of H7N9 infection than those in Zhejiang and Shanghai, if we only take the probability of poultry distribution into consideration. In the study of integrated risk caused by both bird migration and poultry distribution, the higher risk in southeastern provinces occurred during the first 8 weeks, and that in central eastern provinces appeared during Weeks 8 to 12, and that in northeastern provinces since Week 12. Therefore, it is necessary to regulate the poultry markets as long as the poultry-to-poultry transmission is not so well understood. Conclusion: With reference to the reported infection cases, the demonstrated risk mapping results will provide guidance in active surveillance and control of human H7N9 infections by taking intensive intervention in poultry markets. © 2013 Shi et al.; licensee BioMed Central Ltd.


Lu G.,University of Heidelberg | Zhou S.,National Institute of Parasitic Diseases | Zhou S.,Key Laboratory of Parasite and Vector Biology | Zhou S.,Collaborating Center for Malaria | And 5 more authors.
Malaria Journal | Year: 2014

Background: China has already achieved remarkable accomplishments in shrinking the malaria burden since the mid-20th Century. The country now plans to eliminate malaria by the year 2020. Looking at the dynamics of malaria outbreaks during the last decades might provide important information regarding the potential challenges of such an elimination strategy and might help to avoid mistakes of the past. Methods. A systematic review of the published literature (English and Chinese) was conducted to identify malaria outbreaks during the period 1990 until 2013 in China. The main causes of outbreaks as described in these papers were categorized according to whether they were related to population migration, environmental factors, vector and host related factors, and operational problems of the health services. Results: The review identified 36 malaria outbreaks over the 23-year study period, on which sufficient information was available. They mainly occurred in southern and central China involving 12 provinces/autonomous regions. More than half of all outbreaks (21/36, 58%) were attributed at least in part to population migration, with malaria importation to non- or low-endemic areas from high-endemic Chinese areas (13/15) or endemic countries (2/15) having been the most frequent reason (15/21, 71%). Other main causes were problems of the health services (15/36, 42%), in particular poor malaria case management (10/15, 67%), environmental factors (7/36, 19%), and vector and host related factors (5/36, 14%). Conclusions: Beside a number of other challenges, addressing population movement causing malaria appears to be of particular importance to the national malaria programme. Strengthening of surveillance for malaria and early radical treatment of cases should thus be considered among the most important tools for preventing malaria outbreaks and for the final goal of malaria elimination in China. © 2014 Lu et al.; licensee BioMed Central Ltd.


Guo Y.,National Institute of Parasitic Diseases | Guo Y.,Collaborating Center for Malaria | He H.,CAS Institute of Zoology
Fish and Shellfish Immunology | Year: 2014

Freshwater snail Physa acuta has been considered as an important invasive species and medical mollusc. Field investigation has shown that this snail could survive better than other snails in polluted water bodies. To understand the immune mechanisms of P.acuta, suppression subtractive hybridization hepatopancreas cDNA library has been constructed with bacterial challenge. In this study, a full-length cDNA of a novel goose-type lysozyme (PALysG) has been identified from P.acuta by EST and RACE technique. The conservative structure domains sharehigh homology with other molluscan g-type lysozymes including the SLT domain, the substrate binding sites, the catalytic residues, three alpha-helices structures and six molluscan specific cysteines. Meanwhile, PALysG is the first record of goose-type lysozyme in Gastropoda. Real-time PCR indicated that PALysG mRNA had been expressed significantly at high levels in hepatopancreas for 8-48h. PALysG recombinant protein displayed the lytic activity of g-type lysozyme with other organisms against Micrococcus lysodikicus. © 2014 Elsevier Ltd.


Yang G.-J.,Wuxi Institute of Technology | Liu L.,Wuxi Institute of Technology | Zhu H.-R.,Wuxi Institute of Technology | Griffiths S.M.,Chinese University of Hong Kong | And 7 more authors.
The Lancet Infectious Diseases | Year: 2014

Non-communicable diseases dominate the public health arena in China, yet neglected tropical diseases (NTDs) are still widespread and create a substantial burden. We review the geographical distribution, prevalence, and epidemic characteristics of NTDs identified in China caused by helminths, protozoa, bacteria, and viruses. Lymphatic filariasis was eliminated in 2007, but schistosomiasis still affects up to 5% of local village residents in some endemic counties with around 300 000 people infected. China harbours more than 90% of the world's burden of alveolar echinococcosis and food-borne zoonoses are emerging. In 2010, the overall prevalence of soil-transmitted helminth infections caused by Ascaris lumbricoides, Trichuris trichiura, and hookworm was 11·4%, with 6·8% of these infections caused by A lumbricoides. Corresponding figures for food-borne trematodiasis, echinococcosis, and cysticercosis are more than 5%. Dengue, leishmaniasis, leprosy, rabies, and trachoma exist in many areas and should not be overlooked. Transmission of vector-borne diseases can be interrupted; nevertheless, epidemics occur in remote areas, creating a challenge for surveillance and control. Rigorous surveillance, followed by immediate and integrated response packages tailored to specific social and ecological systems, is essential for progress towards the elimination of NTDs in China. © 2014 Elsevier Ltd.

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