生物多样性与传染病风险

近半个世纪以来,新发传染病(多为涉及多宿主的人兽共患病)正在以前所未有的速度不断增加,不仅严重威胁人类健康,还影响着农业生产和野生动物保护。因不同宿主对病原的传播能力具有种间差异,宿主群落结构能够显著地影响病原的传播动态和传染病风险。多样性,作为表征群落结构的重要指标之一,其和传染病风险间的关系(即多样性-疾病关系)是传染病生态学研究的核心问题之一。尤其是“稀释效应”(即提高宿主多样性能够降低疾病风险)的提出引发了广泛的关注。虽然稀释效应得到了众多实证研究的支持,但其普适性仍然存在争议。笔者围绕多样性-疾病关系,介绍稀释效应的生态学机制、普适性及其产生的前提条件。并就3个方向总结了稀释效应的研究进展:①稀释效应的尺度依赖性;②宿主局部灭绝风险和其病原传播能力间的关系;③多样性对疾病风险的身份效应。此外,还分析了近期关于多样性-疾病关系研究框架的拓展,即从物种多样性拓展到谱系多样性;从单一疾病风险拓展到疾病总负担。最后,就未来可能的研究方向提出展望,认为未来研究需探讨分析生境破碎化、非宿主以及群落功能多样性在多样性-疾病关系中的作用。     

Global trends in emerging infectious diseases

Emerging infectious diseases (EIDs) are a significant burden on global economies and public health. Their emergence is thought to be driven largely by socio-economic, environmental and ecological factors, but no comparative study has explicitly analysed these linkages to understand global temporal and spatial patterns of EIDs. Here we analyse a database of 335 EID 'events' (origins of EIDs) between 1940 and 2004, and demonstrate non-random global patterns. EID events have risen significantly over time after controlling for reporting bias, with their peak incidence (in the 1980s) concomitant with the HIV pandemic. EID events are dominated by zoonoses (60.3% of EIDs): the majority of these (71.8%) originate in wildlife (for example, severe acute respiratory virus, Ebola virus), and are increasing significantly over time. We find that 54.3% of EID events are caused by bacteria or rickettsia, reflecting a large number of drug-resistant microbes in our database. Our results confirm that EID origins are significantly correlated with socio-economic, environmental and ecological factors, and provide a basis for identifying regions where new EIDs are most likely to originate (emerging disease 'hotspots'). They also reveal a substantial risk of wildlife zoonotic and vector-borne EIDs originating at lower latitudes where reporting effort is low. We conclude that global resources to counter disease emergence are poorly allocated, with the majority of the scientific and surveillance effort focused on countries from where the next important EID is least likely to originate.     

Origins of major human infectious diseases

Many of the major human infectious diseases, including some now confined to humans and absent from animals, are 'new' ones that arose only after the origins of agriculture. Where did they come from? Why are they overwhelmingly of Old World origins? Here we show that answers to these questions are different for tropical and temperate diseases; for instance, in the relative importance of domestic animals and wild primates as sources. We identify five intermediate stages through which a pathogen exclusively infecting animals may become transformed into a pathogen exclusively infecting humans. We propose an initiative to resolve disputed origins of major diseases, and a global early warning system to monitor pathogens infecting individuals exposed to wild animals.     

The challenge of emerging and re-emerging infectious diseases

Infectious diseases have for centuries ranked with wars and famine as major challenges to human progress and survival. They remain among the leading causes of death and disability worldwide. Against a constant background of established infections, epidemics of new and old infectious diseases periodically emerge, greatly magnifying the global burden of infections. Studies of these emerging infections reveal the evolutionary properties of pathogenic microorganisms and the dynamic relationships between microorganisms, their hosts and the environment.     

北京市2009—2011年传染病与寄生虫病对气温的响应

收集北京市某三级甲等医院2009-2011年的传染病和寄生虫病的急诊就诊资料19 772例,在相关分析的基础上,利用半参数的广义相加模型进行拟合,并对气温进行分段研究.发现不同气温段的气象要素对急诊就诊人数的影响不同.平均气温低于5℃时,气温、气压与急诊就诊人数的关系并不显著(P0.1);平均气温介于5~13℃时,气温每升高1℃,相对危险度为1.032(95%置信区间:1.01,1.06),急诊就诊人数增加3.166%(95%置信区间:0.516%,5.887%);平均气温高于13℃时,气温每升高1℃,相对危险度为1.013(95%置信区间:1.005,1.021),急诊就诊人数增加1.301%(95%置信区间:0.518%,2.091%).得出结论,气温对传染病与寄生虫病具有显著影响,不同气温时就诊人数的增加速率不同,且不同气温区间其他要素的影响也不同.     

从人菌共生的角度探讨生物安全与传染病防控的新思路

近年来发生的与传染病以及生物安全相关事件,如2003年严重急性呼吸系统综合征(SARS)和近期中东呼吸综合征(MERS)等,以及合成生物学技术在人造生命方面的安全风险,提示传染病防控和生物安全的现状不容乐观。如何重构、重建、重塑人类与微生物、尤其是病原微生物之间的关系,已成为重要的现实问题。结合国内外关于人体共生微生物尤其是肠道菌群与慢病相关性的研究进展,从生命起源与协同进化的角度考虑,提出需要正视微生物本身应有的生存空间与生存逻辑,辩证分析并重构人与病毒、人与菌群之间的平衡关系,从人菌共生、人菌共赢的角度出发,通过改善人体共生微生态环境,提高人体免疫力,为传染病防控和生物安全提供新思路。     

中草药防治鳖暴发性传染病

科果介绍鳖常见暴发性传染病的病原和预防措施，重点阐述了实践中筛选出来的防治鳖白点病，红脖子病，疖疮病，白底板病、出血病和腮腺炎等６种暴发性传染病的中草药配伍方剂，及其使用剂量和使用方法。     

Impacts of biodiversity on the emergence and transmission of infectious diseases

Current unprecedented declines in biodiversity reduce the ability of ecological communities to provide many fundamental ecosystem services. Here we evaluate evidence that reduced biodiversity affects the transmission of infectious diseases of humans, other animals and plants. In principle, loss of biodiversity could either increase or decrease disease transmission. However, mounting evidence indicates that biodiversity loss frequently increases disease transmission. In contrast, areas of naturally high biodiversity may serve as a source pool for new pathogens. Overall, despite many remaining questions, current evidence indicates that preserving intact ecosystems and their endemic biodiversity should generally reduce the prevalence of infectious diseases.     

遥感和地理信息系统技术与传染病研究

传染病对人类健康的威胁,是人们生活中最为关注的问题之一.遥感和地理信息系统技术为传染病防制工作的有效开展提供了新的方法.文章探讨了国内外学者应用这一新技术对血吸虫病、莱姆病及疟疾的控制研究.     

Population biology of infectious diseases: Part I.

If the host population is taken to be a dynamic variable (rather than constant, as conventionally assumed), a wider understanding of the population biology of infectious diseases emerges. In this first part of a two-part article, mathematical models are developed, shown to fit data from laboratory experiments, and used to explore the evolutionary relations among transmission parameters. In the second part of the article, to be published in next week's issue, the models are extended to include indirectly transmitted infections, and the general implications for infectious diseases are considered.     

Population biology of infectious diseases: Part II.

In the first part of this two-part article (Nature 280, 361--367), mathematical models of directly transmitted microparasitic infections were developed, taking explicit account of the dynamics of the host population. The discussion is now extended to both microparasites (viruses, bacteria and protozoa) and macroparasites (helminths and arthropods), transmitted either directly or indirectly via one or more intermediate hosts. Consideration is given to the relation between the ecology and evolution of the transmission processes and the overall dynamics, and to the mechanisms that can produce cyclic patterns, or multiple stable states, in the levels of infection in the host population.     

The role of evolution in the emergence of infectious diseases

It is unclear when, where and how novel pathogens such as human immunodeficiency virus (HIV), monkeypox and severe acute respiratory syndrome (SARS) will cross the barriers that separate their natural reservoirs from human populations and ignite the epidemic spread of novel infectious diseases. New pathogens are believed to emerge from animal reservoirs when ecological changes increase the pathogen's opportunities to enter the human population and to generate subsequent human-to-human transmission. Effective human-to-human transmission requires that the pathogen's basic reproductive number, R(0), should exceed one, where R(0) is the average number of secondary infections arising from one infected individual in a completely susceptible population. However, an increase in R(0), even when insufficient to generate an epidemic, nonetheless increases the number of subsequently infected individuals. Here we show that, as a consequence of this, the probability of pathogen evolution to R(0) > 1 and subsequent disease emergence can increase markedly.     

信息的滞后性诱导传染病的周期爆发

通常情况下,一种传染病的爆发往往会引起人们某种行为方式的改变,如减少外出、接种疫苗、注意卫生等,这些行为方式的改变又会对疾病的传播方式和控制效果产生很大影响.为了刻画这类行为方式改变的影响,在本文中提出一个改进的SIRS传播模型：易感染者可以处于两种状态——无保护态（Su）和保护态（Sp）.易感染个体根据对疾病风险的估计在无保护态和保护态之间不断切换,从Su到Sp的转移概率随着感染人数的增加而增加,反之,从Sp到Su的转移概率随着感染人数的增加而减小.同时,我们假设个体对风险的估计依赖于他们对疾病风险信息的了解程度.通过Monte-Carlo和MarkovChain方法,发现对传染病风险判断的滞后性会导致传染病的周期爆发.     

感染性疾病DNA疫苗研究进展（综述）

简要介绍丙型肝炎,爱滋病,结核病,疟疾,麻疹等几种感染性疾病DNA疫苗的重要发现。     

复杂空间接触模式下传染病蔓延模拟建模

针对现代社会越来越复杂的交互行为,提出了一种离散形式的空间分区模型预测传染病蔓延。该模型考虑了现代社会个体之间复杂的空间接触模式,以及真实情况下普遍存在的人群异质性和分布异质性。基于该模型在地理信息系统环境中建立了传染病蔓延的可视化模拟程序。模拟结果表明,该模型能较真实地模拟现实环境下传染病的蔓延过程,可为公共卫生应急中传染病疫情事件的预测预警和应急处置提供决策支持。     

降钙素原、白细胞计数以及C反应蛋白在新生儿感染性疾病中的应用

目的:通过检测患有新生儿感染性疾病的患儿血清中的降钙素原(PCT)、C反应蛋白(CRP)和血液中的白细胞计数(WBC)水平,探讨其对新生儿感染性疾病中辅助诊断作用.方法:选用临床确诊为患有感染性疾病的新生患儿42例,健康新生儿30例,检测其血清中的PCT、CRP以及血液中的WBC,用统计软件Spss 17.0进行数据分析.结果:42例新生患儿中PCT阳性率(PCT≥0.5 ng/mL为阳性)为90.5％,WBC阳性率(WBC＞ 20×109/L为阳性)为28.5％,CRP阳性率(CRP ＞8 mg/L为阳性)为44.7％,三者在新生儿感染性疾病中均升高,但是PCT阳性率明显高于CRP和WBC,存在显著差异性(P＜0.01).结论:PCT、WBC和CRP对新生儿感染性疾病的诊断,鉴别诊断和指导临床早期用药有一定的价值,而且相比于WBC和CRP,PCT是一个能够更早,更灵敏地反映新生儿感染性疾病的指标.