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Symposium on climate change and vector-borne diseases
发布时间:05/08/2014 16:41:05 已被浏览 629

 

 
Symposium on climate change and vector-borne diseases
 
May 13-14, 2014
School of Mathematical Sciences
Nanjing Normal University
 
Climate change is a significant and emerging threat to public health, and changes the way we must look at protecting vulnerable populations. Infectious diseases, especially vector-borne diseases (VBD) are the ones in which the pathogenic microorganism is transmitted from an infected individual to another by an arthropod or other agent, sometimes with other animals serving as intermediary hosts. According to the WHO, nearly half the world's population is infected by vector-borne diseases, resulting in high morbidity and mortality. Important determinants of VBD transmission include: (i) vector survival and reproduction, (ii) the vector's biting rate, and (iii) the pathogen's incubation rate within the vector organism. Vectors, pathogens and hosts each survive and reproduce within a range of optimal climatic conditions: temperature and precipitation are the most important determinants, while landscape variation and composition, sea level elevation, humidity, wind, and daylight duration are also important factors to impact the vector population and virus transmission and spread. There have been mathematical studies of VBD, but the impact of climate on the ecology of diseases was ignored due to a lack of climatic data and difficulties in modeling such impacts. Public health agencies have been running surveillance programs for emerging or re-emerging VBD, but effective forecasting or prediction is still lacking. 
 
 
The goal of this symposium will provide an opportunity for researchers with passion and keen interest in pursuing serious collaborative interdisciplinary work in the field of modeling studies of the impact of climate change on VBDs with focus on mosquito-borne diseases and schistosomiasis.
 
 
 
Organizers: Hui Wan and Huaiping Zhu
Suiyuan Campus
Nanshan Hotel of Nanjing Normal University
Supported by School of Mathematical Science, Nanjing Normal University
Amd Jiangsu Key laboratory  
 
 
 
 
Program 
 
May 13:
8:30 Opening: 
 
8:50 Jacques Blaire, University of Montreal
Mathematical Modeling of Mosquito-Borne Diseases
 
9:30 Hui Wan, Nanjing Normal University
The impact of temperature and resource on malaria transmission
 
10:00 Break
 
10:20 Guihua Li, North University of China
Dynamic behavior analysis in models for vector-borne diseases
 
10:50 Zhigui Lin, Yangzhou University
Spatial spreading mechanisms of West Nile virus with free boundary
 
11:30 Huaiping Zhu York University
Weekly forecasting of culex mosquito abundance, West Nile virus risk and human infection in Ontario, Canada
 
12:00 Lunch break
 
2:00 Guojing Yang, Jiangsu Institute of Parasitic Diseases
Bayesian – based spatial statistical approaches in mapping schistosomiasis risk in China 
 
2:40 Longxing Qi, Anhui University
Model the transmission of schistosomiasis in Tongcheng of China
 
 
3:20 Health break
 
3:40 Meng Fan, Northeast China Normal University
 
4:20 Beate Sander, Public Health Ontario and University of Toronto
Economic Evaluation of Vector-borne Disease Interventions: the Example of West Nile Virus
 
5:00 Dengpeng Jiang, University of Manitoba
Interrupted Time Series Modeling for Impact of a Prolonged MRSA Outbreak on Hospital Costs
 
5:40 Zhen Jin, Shanxi University
 
May 14 Working group discussion on collaborative research
9:00-12:00 
 
 
 
 
Participants:
[To be updated]
 
Title and Abstract
 
Mathematical Modeling of Mosquito-Borne Diseases
Jacques Blaire
University of Montreal
 
Abstract: Mathematical models of transmission of mosquito-borne diseases have been developed for more than a century, earning one of the pioneers of malaria investigations an early Nobel Prize in Physiology or Medicine. A wide range of modeling efforts has tried to address different aspects of the dynamics of transmission, especially for malaria, dengue fever and West Nile virus (in decreasing order of intensity of studies). We will review more recent efforts, emphasizing the influence of changing environmental variables, as well as resource allocation in fighting the occurrence of the disease. An example of malaria transmission in a heterogeneous population, motivated by the situation in Burundi, will be discussed.
 
 
 
Interrupted Time Series Modeling for Impact of a Prolonged MRSA Outbreak on Hospital Costs
Depeng Jiang1, Mathew Muller2, Muhammad Mamdani2
1Department of Community Health Sciences, University of Manitoba, Winnipeg, Canada
2Applied Health Research Center, St Michael’s Hospital, Toronto, Canada
Email: depeng.jiang@med.umanitoba.ca 
 
Background: MRSA (Methicillin-resistant Staphylococcus aureus) is associated with increased healthcare costs for individual colonized and infected patients. An outbreak of MRSA was defined as either an increase in the rate of MRSA cases or a clustering of new cases due to the transmission of a single microbial strain in the health care institution. The overall unit and hospital costs attributable to an MRSA outbreak are not as clearly defined.
 
Objective: To evaluate the impact of a 13 month MRSA outbreak on total hospital and unit costs.  
 
Methods: The interrupted time series analysis was used to compare cost trends on the outbreak unit (a 64 bed internal medicine unit) and a control unit (a 20 bed oncology and HIV unit) over three time periods: pre-outbreak (Jan 2002 to Aug 2006), outbreak (Sep 2006 to Sep 2007) and post-outbreak (Oct 2007 to Jun 2008). For the multiple time series analysis the data for each variable of interest (e.g. total hospital costs per patient) were divided into 90 1-month intervals. Patients were assigned to the pre-outbreak, outbreak and post-outbreak periods based on their day of discharge from the outbreak or control unit. The appropriate ARIMA models were identified based on the monthly data from both the outbreak and control units. Residual partial, inverse and extended autocorrelations, as well as goodness-of-fit Chi-squared statistics were used as diagnostic checks on the ARIMA models. 
 
Results: The patient population on both units was stable in all study periods in terms of age, gender and case-mix group with a mean age of 63.5 yrs and 54.7 yrs on the outbreak and control units, respectively. After adjusting for seasonal variation, no significant changes in total hospital cost per patient were seen on the control unit ($11,125 to $11,565 per patient in the pre-outbreak and outbreak period, respectively). On the outbreak unit, the total hospital cost per patient rose 34.7% during the outbreak (from $9868 to $13,296). A 13.7% increase in mean hospital length of stay, from 7.3 to 8.3 days, partially accounts for these excess costs. These data suggest that the outbreak cost the hospital nearly $10 million over the course of the outbreak.
 
Conclusions: A 13 month MRSA outbreak on our inpatient medical unit resulted in substantial increases in the overall cost per patient on the outbreak unit. These changes were temporally associated with the outbreak and were not seen on a control unit, suggesting the increases in cost were related to the outbreak. 
 
Meng Fan
Northeast China Normal University
 
 
Zhen Jin
Shan’xi University
 
 
Dynamic behavior analysis in models for vector-borne diseases
Guihua Li,
North University of China
 
Abstract: In the talk, we will discuss and analysis the existence and stability of equilibria of vector-borne diseases transmission model. The model exhibits backward bifurcation and may have up to two positive equilibria when the basic reproduction number is less than one; and one, two or three endemic equilibria when the reproduction number is greater than one. By numerical analysis, we study the bifurcations and rich dynamics of the model. Such a vector-borne disease model may undergo a backward bifurcation, saddle node bifurcation, Hopf bifurcations, Bogdanov-Takens bifurcation and cusp bifurcation. The existence of rich and complex dynamics of the model suggest that the control and prevention of vector-borne diseases can be very challenge. 
 
 
The spreading front of West Nile virus and its basic reproduction numbers
Zhigui Lin
Yangzhou University
 
 
In this talk, a diffusion reaction system is proposed to study the spatial spreading of West Nile virus in North America. The free boundary is introduced to describe the spreading front of virus.
To check the effect of spatial heterogeneity and habitat characteristic on the spreading of the virus, four basic reproduction numbers $R_0$, $R_0^N$, $R_0^D$ and $R_0^F(t)$ are given for the WNv models in homogenies environment, in heterogeneous environment with no flux, in heterogeneous environment with hostile boundary and in heterogeneous environment with the free boundary boundary, respectively. Our results show that the virus will spread in the high-risk habitat if the diffusion is slow or the infected habitat is large; In a low-risk habitat, small initial infected habitat, small initial numbers of the virus and fast diffusion are benefit for the virus to vanish. When the virus spreads in the whole habitat, the asymptotic spreading speed is given.
 
 
 
 
 
Model the transmission of schistosomiasis in Tongcheng of China
Longxing Qi,
Anhui University
 
Abstract: Based on the surveillance data in Tongcheng of Anhui province, China, we establish a comprehensive dynamical model for schistosomiasis to study the impact of flooding on the transmission and outbreak of schistosomiasis.
 
 
 
 
 
 
 
 
 
 
Economic Evaluation of Vector-borne Disease Interventions: the Example of West Nile Virus
Beate Sander
Public Health Ontario and University of Toronto
 
Abstract: Currently, no studies assessing the cost-effectiveness of personal and community-level WNV mitigation strategies exist. However, a rigorous assessment of current and future preventative options is essential for local public health response and strategic decision-making. In this talk, I will provide a brief introduction to economic evaluation applied to public health questions, particularly infectious diseases and discuss specific challenges in assessing the effectiveness and cost-effectiveness of intervention strategies for vector-borne diseases. I will describe our recently CIHR funded study, which is a joint project between Public Health Ontario and York University. The goal of the study is to evaluate the cost-effectiveness of WNV interventions strategies using a computer simulation model. The discussion will highlight key methodological considerations and the need for multidisciplinary approaches
 
 
 
 
 
 
 
 
The impact of temperature and resource on malaria transmission
Hui Wan
Nanjing Normal University
 
Abstract: In this talk, we extend the famous Ross's model to establish a new model for malaria to incorporate the impact of blood meal resource for mosquitoes and temperature on the transmission of malaria. It is shown that with the new growth rate for mosquitoes, the transmission dynamics of malaria becomes more complex and the Hopf bifurcation may occur which induces sustained oscillations not only in the mosquito population but also in the infected human population. Our results also suggest that the abundance of blood meal resource for mosquitoes can be a factor which is important to characterize the transmission dynamics of malaria in a region. The impact of maturation time delay related to temperature changes is also analyzed which suggests that increasing the temperature exacerbates the transmission of malaria.
 
 
 
 
 
 
Impacts of climate changes on the transmission of schisotosomiasis and malaria in China
Guojing Yang,
Jiangsu Institute of Parasitic Diseases
 
 
 
There is a growing body of literature documenting the impacts of climate change on physical and biological systems, including human health. An area that has received particular attention is the potential impact of global warming on shifts in the spatio-temporal distribution of disease vectors, and hence the frequency and transmission dynamics of vector-borne diseases. In today’s talk, we are going to present studies which we have done to assess the potential impact of climate change on the transmission of schistosomiasis and malaria in China by mathematical models, coupled with geographical information system (GIS) and remote sensing techniques.
 
  
 
 
.
 
 
Weekly forecasting of culex mosquito abundance, West Nile virus risk and human infection in Ontario, Canada
Huaiping Zhu
York University
 
West Nile virus is a mosquito-borne flavivirus typically transmitted between birds and mosquitoes, and can infect humans and other domestic mammals. It has become a threat for public health since 1999 in North America. Like other mosquito-borne or vector-borne diseases, the transmission and dynamics of the West Nile virus can be very complicated due to climate and environmental impact on vector mosquitoes density, seasonal impact on amplification host birds and biting incidences of the vectors. In this talk, I will briefly introduce our effort on using surveillance data, weather and landscape data to model and weekly real-time forecast of culex mosquito abundance, minimum infection rate (MIR) for risk assessment and human infection cases of West Nile virus in Ontario, Canada. This is a joint effort of LAMPS interdisciplinary network including Public Health Agencies of both federal and provincial government as well as selected Health Regions/Units towards the development of climate change adaptation toolkit for public health, and the establishment of Early Warning and Response System (EWARS) for vector-borne diseases. 
 
 
 
 
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