Determinants of emerging and re-emerging infectious diseases.

In the 1960s and 1970s, many public health experts assumed that infectious diseases could at long last be conquered as had occurred with smallpox. In the last two decades, reports warned that infectious diseases were clearly not a problem of the past. They could not be considered as a unique or isolated event of wild and faraway regions, but penetrated every corner of the globe. Emerging infectious diseases have been recently described as clinically distinct conditions whose incidence in humans has increased regionally or worldwide within the past two decades. Emergence may be due to the introduction of new agents to or the recognition of an existing disease that has gone undetected, and re-emergence may describe the re-appearance of known diseases after a decline in incidence. In this article a global, multidisciplinary and integrated approach in different fields of demography, epidemiology, economy, ecology, anthropology and environment at science has been considered to describe the different determinants responsible for the emergence and re-emergence of infectious diseases.     

Surveillance of emerging infectious diseases for biosecurity

Science China Life Sciences - Emerging infectious diseases, such as COVID-19, continue to pose significant threats to human beings and their surroundings. In addition, biological warfare,...     

Climate change and emerging infectious diseases

The ranges of infectious diseases and vectors are changing in altitude, along with shifts in plant communities and the retreat of alpine glaciers. Additionally, extreme weather events create conditions conducive to clusters of insect-, rodent- and water-borne diseases. Accelerating climate change carries profound threats for public health and society.     

Controlling emerging infectious diseases like SARS

To control emerging infectious diseases like SARS, it is necessary to resort to basic control measures that limit exposures to infectious individuals. These measures include isolating cases at diagnosis, quarantining household members and tracing contacts of diagnosed cases, providing the community with advice on how to reduce exposures, and closing schools. To justify such intervention it is important to understand how well each of these measures helps to limit transmission. In this paper, we determine the effect of a number of different interventions on the effective reproduction number and estimate requirements to achieve elimination of the infectious disease. We find that the strategy of tracing and quarantining contacts of diagnosed cases can be very successful in reducing transmission.     

Lurking in the shadows: emerging rodent infectious diseases

Rodent parvoviruses, Helicobacter spp., murine norovirus, and several other previously unknown infectious agents have emerged in laboratory rodents relatively recently. These agents have been discovered serendipitously or through active investigation of atypical serology results, cell culture contamination, unexpected histopathology, or previously unrecognized clinical disease syndromes. The potential research impact of these agents is not fully known. Infected rodents have demonstrated immunomodulation, tumor suppression, clinical disease (particularly in immunodeficient rodents), and histopathology. Perturbations of organismal and cellular physiology also likely occur. These agents posed unique challenges to laboratory animal resource programs once discovered; it was necessary to develop specific diagnostic assays and an understanding of their epidemiology and transmission routes before attempting eradication, and then evaluate eradication methods for efficacy. Even then management approaches varied significantly, from apathy to total exclusion, and such inconsistency has hindered the sharing and transfer of rodents among institutions, particularly for genetically modified rodent models that may not be readily available. As additional infectious agents are discovered in laboratory rodents in coming years, much of what researchers have learned from experiences with the recently identified pathogens will be applicable. This article provides an overview of the discovery, detection, and research impact of infectious agents recently identified in laboratory rodents. We also discuss emerging syndromes for which there is a suspected infectious etiology, and the unique challenges of managing newly emerging infectious agents.     

Emerging and re-emerging infectious diseases: influenza as a prototype of the host-pathogen balancing act

To respond to emerging and re-emerging infections, it is necessary to understand the interactions between microbial pathogens and their hosts and the impact of environmental and social factors on these interactions. The importance of understanding host-pathogen interactions is underscored by the emergence of virulent H5N1 avian influenza viruses and their transmission to humans, and the potential pandemic threat they pose.     

Timely identification of optimal control strategies for emerging infectious diseases

Background

Health authorities must rely on quarantine, isolation, and other non-pharmaceutical interventions to contain outbreaks of newly emerging human diseases.

Methods

We modeled a generic disease caused by a pathogen apparently transmitted by close interpersonal contact, but about which little else is known. In our model, people may be infectious while incubating or during their prodrome or acute illness. We derived an expression for ℜ, the reproduction number, took its partial derivatives with respect to control parameters, and encoded these analytical results in a user-friendly Mathematica™ notebook. With biological parameters for SARS estimated from the initial case series in Hong Kong and infection rates from hospitalizations in Singapore, we determined ℜ's sensitivity to control parameters.

Results

Stage-specific infection rate estimates from cases hospitalized before quarantine began exceed those from the entire outbreak, but are qualitatively similar: infectiousness was negligible until symptom onset, and increased 10-fold from prodrome to acute illness. Given such information, authorities might instead have emphasized a strategy whose efficiency more than compensates for any possible reduction in efficacy.

Conclusions

In future outbreaks of new human diseases transmitted via close interpersonal contact, it should be possible to identify the optimal intervention early enough to facilitate effective decision-making.     

Human T-cell immunity against the emerging and re-emerging viruses

Over the past decade, we have seen an alarming number of high-profile outbreaks of newly emerging and re-emerging viruses. Recent outbreaks of avian influenza viruses, Middle East respiratory syndrome coronaviruses, Zika virus and Ebola virus present great threats to global health. Considering the pivotal role of host T-cell immunity in the alleviation of symptoms and the clearance of viruses in patients, there are three issues to be primarily concerned about T-cell immunity when a new virus emerges: first, does the population possess pre-existing T-cells against the new virus through previous infections of genetically relevant viruses; second, does a proper immune response arise in the patients to provide protection through an immunopathogenic effect; lastly, how long can the virus-specific immune memory persist. Herein, we summarize the current updates on the characteristics of human T-cell immunological responses against recently emerged or re-emerged viruses, and emphasize the necessity for timely investigation on the T-cell features of these viral diseases, which may provide beneficial recommendations for clinical diagnosis and vaccine development.     

Ecosystem dynamics, biological diversity and emerging infectious diseases

In this article, we summarize the major scientific developments of the last decade on the transmission of infectious agents in multi-host systems. Almost sixty percent of the pathogens that have emerged in humans during the last 30-40 years are of animal origin and about sixty percent of them show an important variety of host species besides humans (3 or more possible host species). In this review, we focus on zoonotic infections with vector-borne transmission and dissect the contrasting effects that a multiplicity of host reservoirs and vectors can have on their disease dynamics. We discuss the effects exerted by host and vector species richness and composition on pathogen prevalence (i.e., reduction, including the dilution effect, or amplification). We emphasize that, in multiple host systems and for vector-borne zoonotic pathogens, host reservoir species and vector species can exert contrasting effect locally. The outcome on disease dynamics (reduced pathogen prevalence in vectors when the host reservoir species is rich and increased pathogen prevalence when the vector species richness increases) may be highly heterogeneous in both space and time. We then ask briefly how a shift towards a more systemic perspective in the study of emerging infectious diseases, which are driven by a multiplicity of hosts, may stimulate further research developments. Finally, we propose some research avenues that take better into account the multi-host species reality in the transmission of the most important emerging infectious diseases, and, particularly, suggest, as a possible orientation, the careful assessment of the life-history characteristics of hosts and vectors in a community ecology-based perspective.     

Coronaviruses: emerging and re-emerging pathogens in humans and animals

The severe acute respiratory syndrome coronavirus (SARS-CoV) and recently emerged Middle East respiratory syndrome coronavirus (MERS-CoV) epidemics have proven the ability of coronaviruses to cross species barrier and emerge rapidly in humans. Other coronaviruses such as porcine epidemic diarrhea virus (PEDV) are also known to cause major disease epidemics in animals wiith huge economic loss. This special issue in Virology Journal aims to highlight the advances and key discoveries in the animal origin, viral evolution, epidemiology, diagnostics and pathogenesis of the emerging and re-emerging coronaviruses in both humans and animals.     

严重危害人类的8种病毒性传染病

当今,高致病性禽流感(HPAI)肆虐全球,获得性免疫缺损综合症(艾滋病,AIDS)对人类的感染也在快速增加;病毒性肝炎,特别是乙型肝炎(乙肝,Hepatitis B)使全球数亿人(我国约1．3亿)成为病毒的感染者。而乙肝病毒高几率的母婴传播,严重影响后代的身体健康,已成为影响人类健康的重大问题：2002-2003年起在亚     

Emerging and re-emerging bacterial diseases in India

There has been a remarkable progress in the prevention, control and even eradication of infectious diseases with improved hygiene and development of antimicrobials and vaccines. However, infectious diseases still remain a leading cause of global disease burden with high morbidity and mortality especially in the developing world. Furthermore, there have been threats of new diseases during the past three decades due to the evolution and adaptation of microbes and the re-emergence of old diseases due to the development of antimicrobial resistance and the capacity to spread to new geographic areas. The impact of the emerging and re-emerging diseases in India has been tremendous at socioeconomic and public health levels. Their control requires continuing surveillance, research and training, better diagnostic facilities and improved public health system. Emerging and reemerging zoonotic diseases, foodborne and waterborne diseases and diseases caused by multiresistant organisms constitute the major threats in India. This review of bacterial emerging and re-emerging diseases should be of critical importance to microbiologists, clinicians, public health personnel and policy makers in India.     

Systematics and emerging infectious diseases: from management to solution

The crisis of emerging infectious disease stems from the absence of comprehensive taxonomic inventories of the world's parasites, which includes the world's pathogens. Recent technological developments raise hopes that the global inventory of species, including potential pathogens, can be accomplished in a timely and cost-effective manner. The phylogenetics revolution initiated by systematists provides a means by which information about pathogen transmission dynamics can be placed in a predictive framework. Increasingly, that information is widely available in digital form on the Internet. Systematic biology is well positioned to play a crucial role in efforts to be proactive in the arena of emerging parasitic and infectious diseases.