SARS molecular epidemiology: a Chinese fairy tale of controlling an emerging zoonotic disease in the genomics era

SARS-CoV-2 Transmission by Arthropod Vectors: A Scoping Review

COVID-19 is a respiratory disease of worldwide importance as it has brought enormous health problems to the world's population. The best-known way of transmission of the virus is through aerosolization. However, research is needed to explore other transmission routes. Researchers hypothesized that arthropods could transmit SARs-CoV-2. This study is aimed at reviewing research on arthropods as possible reservoirs and/or vectors of SARS-CoV-2, the causative agent of COVID-19. Following PRISMA guidelines, we conducted a systematic review using several electronic databases/academic searches with the search terms “arthropods,” “coronavirus,” and “transmission.” A total of 64 unique articles were identified, of which 58 were included in the review. The SARS-CoV-2 virus is tiny and invisible to the naked eye, and its presence in stools, droplets, and surfaces was detected. One doubt is whether insects can transmit the virus from one place to another. Thus, a healthy carrier of the COVID-19 virus can be at the root of the contamination of their community or their family through the transport of the virus by insects from the interior (flies, cockroaches, etc.) from their feces and food surfaces. Hygiene care within communities and families becomes a prime factor. Coronavirus infection is a significant public health problem around the world. The prevention and control of outbreaks remain very important, even with the production of new vaccines. The main option to achieve this is the proper management of the transmission of the virus. The registry of infected people is currently the basis for the transmission of COVID-19. However, questions about the possibility of infection from other sources and its prevention are not receiving adequate attention. Numerous studies have shown the possibility that SARS-COV-2 fragments could have a longer life than shed respiratory droplets. Also, this virus is larger than those of other coronavirus families.

Immune Profiling of COVID-19 in Correlation with SARS and MERS

Acute respiratory distress syndrome (ARDS) is a major complication of the respiratory illness coronavirus disease 2019, with a death rate reaching up to 40%. The main underlying cause of ARDS is a cytokine storm that results in a dysregulated immune response. This review discusses the role of cytokines and chemokines in SARS-CoV-2 and its predecessors SARS-CoV and MERS-CoV, with particular emphasis on the elevated levels of inflammatory mediators that are shown to be correlated with disease severity. For this purpose, we reviewed and analyzed clinical studies, research articles, and reviews published on PubMed, EMBASE, and Web of Science. This review illustrates the role of the innate and adaptive immune responses in SARS, MERS, and COVID-19 and identifies the general cytokine and chemokine profile in each of the three infections, focusing on the most prominent inflammatory mediators primarily responsible for the COVID-19 pathogenesis. The current treatment protocols or medications in clinical trials were reviewed while focusing on those targeting cytokines and chemokines. Altogether, the identified cytokines and chemokines profiles in SARS-CoV, MERS-CoV, and SARS-CoV-2 provide important information to better understand SARS-CoV-2 pathogenesis and highlight the importance of using prominent inflammatory mediators as markers for disease diagnosis and management. Our findings recommend that the use of immunosuppression cocktails provided to patients should be closely monitored and continuously assessed to maintain the desirable effects of cytokines and chemokines needed to fight the SARS, MERS, and COVID-19. The current gap in evidence is the lack of large clinical trials to determine the optimal and effective dosage and timing for a therapeutic regimen.

Characterization of SARS-CoV-2 ORF6 deletion variants detected in a nosocomial cluster during routine genomic surveillance, Lyon, France

During routine molecular surveillance of SARS-CoV-2 performed at the National Reference Center of Respiratory Viruses (Lyon, France) (n = 229 sequences collected February-April 2020), two frameshifting deletions were detected in the open reading frame 6, at the same position (27267). While a 26-nucleotide deletion variant (D26) was only found in one nasopharyngeal sample in March 2020, the 34-nucleotide deletion (D34) was found within a single geriatric hospital unit in 5/9 patients and one health care worker in April 2020. Phylogeny analysis strongly suggested a nosocomial transmission of D34, with potential fecal transmission, as also identified in a stool sample. No difference in disease severity was observed between patients hospitalized in the geriatric unit infected with WT or D34. In vitro D26 and D34 characterization revealed comparable replication kinetics with the wild-type (WT), but differential host immune responses. While interferon-stimulated genes were similarly upregulated after infection with WT and ORF6 variants, the latter specifically induced overexpression of 9 genes coding for inflammatory cytokines in the NF-kB pathway, including CCL2/MCP1, PTX3, and TNFα, for which high plasma levels have been associated with severe COVID-19. Our findings emphasize the need to monitor the occurrence of ORF6 deletions and assess their impact on the host immune response.

A Review on the Development of Gold and Silver Nanoparticles-Based Biosensor as a Detection Strategy of Emerging and Pathogenic RNA Virus

The emergence of highly pathogenic and deadly human coronaviruses, namely SARS-CoV and MERS-CoV within the past two decades and currently SARS-CoV-2, have resulted in millions of human death across the world. In addition, other human viral diseases, such as mosquito borne-viral diseases and blood-borne viruses, also contribute to a higher risk of death in severe cases. To date, there is no specific drug or medicine available to cure these human viral diseases. Therefore, the early and rapid detection without compromising the test accuracy is required in order to provide a suitable treatment for the containment of the diseases. Recently, nanomaterials-based biosensors have attracted enormous interest due to their biological activities and unique sensing properties, which enable the detection of analytes such as nucleic acid (DNA or RNA), aptamers, and proteins in clinical samples. In addition, the advances of nanotechnologies also enable the development of miniaturized detection systems for point-of-care (POC) biosensors, which could be a new strategy for detecting human viral diseases. The detection of virus-specific genes by using single-stranded DNA (ssDNA) probes has become a particular interest due to their higher sensitivity and specificity compared to immunological methods based on antibody or antigen for early diagnosis of viral infection. Hence, this review has been developed to provide an overview of the current development of nanoparticles-based biosensors that target pathogenic RNA viruses, toward a robust and effective detection strategy of the existing or newly emerging human viral diseases such as SARS-CoV-2. This review emphasizes the nanoparticles-based biosensors developed using noble metals such as gold (Au) and silver (Ag) by virtue of their powerful characteristics as a signal amplifier or enhancer in the detection of nucleic acid. In addition, this review provides a broad knowledge with respect to several analytical methods involved in the development of nanoparticles-based biosensors for the detection of viral nucleic acid using both optical and electrochemical techniques.

Therapeutic Potential of Exploiting Autophagy Cascade Against Coronavirus Infection

Since its emergence in December 2019 in Wuhan, China, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) created a worldwide pandemic of coronavirus disease (COVID-19) with nearly 136 million cases and approximately 3 million deaths. Recent studies indicate that like other coronaviruses, SARS-CoV-2 also hijacks or usurps various host cell machineries including autophagy for its replication and disease pathogenesis. Double membrane vesicles generated during initiation of autophagy cascade act as a scaffold for the assembly of viral replication complexes and facilitate RNA synthesis. The use of autophagy inhibitors - chloroquine and hydroxychloroquine initially appeared to be as a potential treatment strategy of COVID-19 patients but later remained at the center of debate due to high cytotoxic effects. In the absence of a specific drug or vaccine, there is an urgent need for a safe, potent as well as affordable drug to control the disease spread. Given the intricate connection between autophagy machinery and viral pathogenesis, the question arises whether targeting autophagy pathway might show a path to fight against SARS-CoV-2 infection. In this review we will discuss about our current knowledge linking autophagy to coronaviruses and how that is being utilized to repurpose autophagy modulators as potential COVID-19 treatment.

The histo-blood group antigens of the host cell may determine the binding of different viruses such as SARS-CoV-2

Viruses have caused the death of millions of people worldwide. Specifically, human viruses are grouped into 21 families, including the family of coronaviruses (CoVs). In December 2019, in Wuhan, China, a new human CoV was identified, SARS-CoV-2. The first step of the infection mechanism of the SARS-CoV-2 in the human host is adhesion, which occurs through the S glycoprotein that is found in diverse human organs. Another way through which SARS-CoV-2 could possibly attach to the host's cells is by means of the histo-blood group antigens. In this work, we have reviewed the mechanisms by which some viruses bind to the histo-blood group antigens, which could be related to the susceptibility of the individual and are dependent on the histo-blood group.

Fundamentals of genomic epidemiology, lessons learned from the coronavirus disease 2019 (COVID-19) pandemic, and new directions

The coronavirus disease 2019 (COVID-19) pandemic was one of the significant causes of death worldwide in 2020. The disease is caused by severe acute coronavirus syndrome (SARS) coronavirus 2 (SARS-CoV-2), an RNA virus of the subfamily Orthocoronavirinae related to 2 other clinically relevant coronaviruses, SARS-CoV and MERS-CoV. Like other coronaviruses and several other viruses, SARS-CoV-2 originated in bats. However, unlike other coronaviruses, SARS-CoV-2 resulted in a devastating pandemic. The SARS-CoV-2 pandemic rages on due to viral evolution that leads to more transmissible and immune evasive variants. Technology such as genomic sequencing has driven the shift from syndromic to molecular epidemiology and promises better understanding of variants. The COVID-19 pandemic has exposed critical impediments that must be addressed to develop the science of pandemics. Much of the progress is being applied in the developed world. However, barriers to the use of molecular epidemiology in low- and middle-income countries (LMICs) remain, including lack of logistics for equipment and reagents and lack of training in analysis. We review the molecular epidemiology literature to understand its origins from the SARS epidemic (2002-2003) through influenza events and the current COVID-19 pandemic. We advocate for improved genomic surveillance of SARS-CoV and understanding the pathogen diversity in potential zoonotic hosts. This work will require training in phylogenetic and high-performance computing to improve analyses of the origin and spread of pathogens. The overarching goals are to understand and abate zoonosis risk through interdisciplinary collaboration and lowering logistical barriers.

Possibility for reverse zoonotic transmission of SARS-CoV-2 to free-ranging wildlife: A case study of bats

The COVID-19 pandemic highlights the substantial public health, economic, and societal consequences of virus spillover from a wildlife reservoir. Widespread human transmission of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) also presents a new set of challenges when considering viral spillover from people to naïve wildlife and other animal populations. The establishment of new wildlife reservoirs for SARS-CoV-2 would further complicate public health control measures and could lead to wildlife health and conservation impacts. Given the likely bat origin of SARS-CoV-2 and related beta-coronaviruses (β-CoVs), free-ranging bats are a key group of concern for spillover from humans back to wildlife. Here, we review the diversity and natural host range of β-CoVs in bats and examine the risk of humans inadvertently infecting free-ranging bats with SARS-CoV-2. Our review of the global distribution and host range of β-CoV evolutionary lineages suggests that 40+ species of temperate-zone North American bats could be immunologically naïve and susceptible to infection by SARS-CoV-2. We highlight an urgent need to proactively connect the wellbeing of human and wildlife health during the current pandemic and to implement new tools to continue wildlife research while avoiding potentially severe health and conservation impacts of SARS-CoV-2 "spilling back" into free-ranging bat populations.

Antiviral Activity of Nanomaterials against Coronaviruses

One of the challenges facing by world nowadays is the generation of new pathogens that cause public health issues. Coronavirus (CoV) is one of the severe pathogens that possess the RNA (ribonucleic acid) envelop, and extensively infect humans, birds, and other mammals. The novel strain "SARS-CoV-2" (severe acute respiratory syndrome coronavirus-2) causes deadly infection all over the world and presents a pandemic situation nowadays. The SARS-CoV-2 has 40 different strains that create a worrying situation for health authorities. The virus develops serious pneumonia in infected persons and causes severe damage to the lungs. There is no vaccine available for this virus up to present. To cure this type of infections by making vaccines and antiviral drugs is still a major challenge for researchers. Nanotechnology covering a multidisciplinary field may find the solution to this lethal infection. The interaction of nanomaterials and microorganisms is considered as a potential treatment method because the nanomaterials owe unique physicochemical properties. The aim of this review is to present an overview of previous and recent studies of nanomaterials against coronaviruses and to provide possible new strategies for upcoming research using the nanotechnology platform.

Valinomycin as a potential antiviral agent against coronaviruses: A review

Human coronaviruses (HCoVs), including severe acute respiratory syndrome coronavirus (SARS-CoV), Middle East respiratory syndrome coronavirus (MERS-CoV), and severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), have been resulting in global epidemics with heavy morbidity and mortality. Unfortunately, there are currently no specific medicines that can better treat these coronaviruses. Drug repurposing is an effective and economical strategy for drug discovery from existing drugs, natural products, and synthetic compounds. In this review, the broad-spectrum antiviral activity of valinomycin (VAL), especially its activity against coronaviruses such as SARS-CoV, MERS-CoV, human coronavirus OC43 (HCoV-OC43), were summarized, it highlights that VAL has tremendous potential for use as a novel antiviral agent against SARS-CoV-2.

Multiscale model for the optimal design of pedestrian queues to mitigate infectious disease spread

There is direct evidence for the spread of infectious diseases such as influenza, SARS, measles, and norovirus in locations where large groups of people gather at high densities e.g. theme parks, airports, etc. The mixing of susceptible and infectious individuals in these high people density man-made environments involves pedestrian movement which is generally not taken into account in modeling studies of disease dynamics. We address this problem through a multiscale model that combines pedestrian dynamics with stochastic infection spread models. The pedestrian dynamics model is utilized to generate the trajectories of motion and contacts between infected and susceptible individuals. We incorporate this information into a stochastic infection dynamics model with infection probability and contact radius as primary inputs. This generic model is applicable for several directly transmitted diseases by varying the input parameters related to infectivity and transmission mechanisms. Through this multiscale framework, we estimate the aggregate numbers and probabilities of newly infected people for different winding queue configurations. We find that the queue configuration has a significant impact on disease spread for a range of infection radii and transmission probabilities. We quantify the effectiveness of wall separators in suppressing the disease spread compared to rope separators. Further, we find that configurations with short aisles lower the infection spread when rope separators are used.

Novel Bat Alphacoronaviruses in Southern China Support Chinese Horseshoe Bats as an Important Reservoir for Potential Novel Coronaviruses

While bats are increasingly recognized as a source of coronavirus epidemics, the diversity and emergence potential of bat coronaviruses remains to be fully understood. Among 1779 bat samples collected in China, diverse coronaviruses were detected in 32 samples from five different bat species by RT-PCR. Two novel alphacoronaviruses, Rhinolophus sinicus bat coronavirus HKU32 (Rs-BatCoV HKU32) and Tylonycteris robustula bat coronavirus HKU33 (Tr-BatCoV HKU33), were discovered from Chinese horseshoe bats in Hong Kong and greater bamboo bats in Guizhou Province, respectively. Genome analyses showed that Rs-BatCoV HKU32 is closely related to BatCoV HKU10 and related viruses from diverse bat families, whereas Tr-BatCoV HKU33 is closely related to BtNv-AlphaCoV and similar viruses exclusively from bats of Vespertilionidae family. The close relatedness of Rs-BatCoV HKU32 to BatCoV HKU10 which was also detected in Pomona roundleaf bats from the same country park suggests that these viruses may have the tendency of infecting genetically distant bat populations of close geographical proximity with subsequent genetic divergence. Moreover, the presence of SARSr-CoV ORF7a-like protein in Rs-BatCoV HKU32 suggests a common evolutionary origin of this accessory protein with SARS-CoV, also from Chinese horseshoe bats, an apparent reservoir for coronavirus epidemics. The emergence potential of Rs-BatCoV HKU32 should be explored.

Global Epidemiology of Bat Coronaviruses

Bats are a unique group of mammals of the order Chiroptera. They are highly diversified and are the group of mammals with the second largest number of species. Such highly diversified cell types and receptors facilitate them to be potential hosts of a large variety of viruses. Bats are the only group of mammals capable of sustained flight, which enables them to disseminate the viruses they harbor and enhance the chance of interspecies transmission. This article aims at reviewing the various aspects of the global epidemiology of bat coronaviruses (CoVs). Before the SARS epidemic, bats were not known to be hosts for CoVs. In the last 15 years, bats have been found to be hosts of >30 CoVs with complete genomes sequenced, and many more if those without genome sequences are included. Among the four CoV genera, only alphaCoVs and betaCoVs have been found in bats. As a whole, both alphaCoVs and betaCoVs have been detected from bats in Asia, Europe, Africa, North and South America and Australasia; but alphaCoVs seem to be more widespread than betaCoVs, and their detection rate is also higher. For betaCoVs, only those from subgenera Sarbecovirus, Merbecovirus, Nobecovirus and Hibecovirus have been detected in bats. Most notably, horseshoe bats are the reservoir of SARS-CoV, and several betaCoVs from subgenus Merbecovirus are closely related to MERS-CoV. In addition to the interactions among various bat species themselves, bat⁻animal and bat⁻human interactions, such as the presence of live bats in wildlife wet markets and restaurants in Southern China, are important for interspecies transmission of CoVs and may lead to devastating global outbreaks.

Public Health Surveillance: A Vital Alert and Response Function

Ungchusak, Heymann and Pollack address the critical global issue of public health surveillance. They describe how epidemiologists collect and use surveillance data to detect unusual events or outbreaks and to guide control programmes. Drawing on their combined international experience, the authors explain the vital role that data play in alerting authorities to respond to outbreaks such as Severe Acute Respiratory Syndrome, Ebola, Zika virus and Avian influenza. They point to the importance of sharing information globally while ensuring equal benefits to providers of data, coordinating surveillance activities across sectors, building capacity for surveillance and coordinating national surveillance activities. The authors emphasise the need for enhanced global cooperation to prepare for future public health emergencies of international concern.

Phylogenetic Insight into Zika and Emerging Viruses for a Perspective on Potential Hosts

Global viral diversity is substantial, but viruses that contribute little to the public health burden or to agricultural damage receive minimal attention until a seemingly unimportant virus becomes a threat. The Zika virus (ZIKV) illustrated this, as there was limited information and awareness of the virus when it was identified as a public health emergency in February 2016. Predicting which virus may pose a future threat is difficult. This is in part because significant knowledge gaps in the basic biology and ecology of an emerging virus can impede policy development, delay decision making, and hinder public health action. We suggest using a phylogenetic framework of pathogens and their infected host species for insight into which animals may serve as reservoirs. For example, examining flaviviruses closely related to ZIKV, the phylogenetic framework indicates New World monkeys are the most likely candidates to be potential reservoirs for ZIKV. Secondarily, mammals that are in close proximity to humans should be considered because of the increased opportunity for pathogen exchange. The increase in human-mediated environmental change is accelerating the probability of another previously overlooked virus becoming a significant concern. By investing in basic science research and organizing our knowledge into an evolutionary framework, we will be better prepared to respond to the next emerging infectious disease.

Evolution of SARS Coronavirus and the Relevance of Modern Molecular Epidemiology

The severe acute respiratory syndrome (SARS) is the first major zoonotic infectious disease of the 21st Century. The disease, originally termed “atypical pneumonia,” was first recognized in November 2002 in Guangdong Province, China, which spread rapidly to 26 countries within 5 months and eventually led to 8096 human infection cases and 774 deaths. A previously unrecognized coronavirus, named SARS coronavirus (SARS-CoV), was later identified as the causative agent of SARS. Subsequent investigation indicated that the source of the human infections originated most likely from infected wildlife animals traded in the live animal markets, with masked palm civets considered the most prominent and important carrier. Large-scale culling of civets appeared to be effective in preventing further outbreaks in the region. Subsequent epidemiological studies showed that civets are intermediate host of SARS-CoV and bats are the likely natural reservoir of SARS-CoV and a large number of SARS-like coronaviruses (SL-CoVs). Detailed analysis of the massive SARS-CoV genomic sequence data indicated that SARS-CoV experienced a strong selection pressure during different outbreak phases in humans as well as interspecies transmission from animals to humans. The spike glycoprotein (S) of SARS-CoV plays a key role in virus–host interaction and hence is a key determinant of interspecies transmission. It has been shown that minor changes of amino acid (aa) residues in the S protein could lead to dramatic changes in virus susceptibility in animal and human hosts. This chapter focuses on the genetics and evolution of SARS-CoVs and SL-CoVs in humans, civets, and bats. The events of SARS outbreaks and the accompanying response activities highlight the importance of modern molecular epidemiology in disease investigation and the urgent need to broaden the screening and investigation of unknown viruses in wildlife animals.

Molecular Evolution of Human Coronavirus Genomes

Human coronaviruses (HCoVs), including SARS-CoV and MERS-CoV, are zoonotic pathogens that originated in wild animals. HCoVs have large genomes that encode a fixed array of structural and nonstructural components, as well as a variety of accessory proteins that differ in number and sequence even among closely related CoVs. Thus, in addition to recombination and mutation, HCoV genomes evolve through gene gains and losses. In this review we summarize recent findings on the molecular evolution of HCoV genomes, with special attention to recombination and adaptive events that generated new viral species and contributed to host shifts and to HCoV emergence. VIDEO ABSTRACT.

Identification of new respiratory viruses in the new millennium

The rapid advancement of molecular tools in the past 15 years has allowed for the retrospective discovery of several new respiratory viruses as well as the characterization of novel emergent strains. The inability to characterize the etiological origins of respiratory conditions, particularly in children, led several researchers to pursue the discovery of the underlying etiology of disease. In 2001, this led to the discovery of human metapneumovirus (hMPV) and soon following that the outbreak of Severe Acute Respiratory Syndrome coronavirus (SARS-CoV) promoted an increased interest in coronavirology and the latter discovery of human coronavirus (HCoV) NL63 and HCoV-HKU1. Human bocavirus, with its four separate lineages, discovered in 2005, has been linked to acute respiratory tract infections and gastrointestinal complications. Middle East Respiratory Syndrome coronavirus (MERS-CoV) represents the most recent outbreak of a completely novel respiratory virus, which occurred in Saudi Arabia in 2012 and presents a significant threat to human health. This review will detail the most current clinical and epidemiological findings to all respiratory viruses discovered since 2001.

A review of infection control in community healthcare: new challenges but old foes

The demographics of the healthcare population are changing, with an ever-greater proportion of people being treated outside the traditional hospital setting through community healthcare. This shift in the way that healthcare is delivered raises new concerns over community healthcare-associated infections (HCAIs). A literature search between 2000 and December 2013 was conducted in databases including PubMed, SciVerse ScienceDirect and Google Scholar. National and international guideline and policy documents were searched using Google. Many terms were used in the literature searches, including ‘nosocomial’, ‘healthcare infection’, ‘community’ and ‘nursing home’. The rates of HCAI in community healthcare are similar to the rates found in the acute hospital setting, but the types of infection differ, with a greater focus on urinary tract infections (UTIs) in the community and ventilator-associated pneumonias in the hospital setting. Patients who acquire a community HCAI are more likely to exhibit reduced physical condition, have increased levels of morbidity and have higher mortality rates than individuals without infection. Infection control programmes have been developed worldwide to reduce the rates of hospital HCAIs. Such interventions are equally as valid in the community, but how best to implement them and their subsequent impact are much less well understood. The future is clear: HCAIs in the community are going to become an ever-increasing burden and it is critical that our approach to these infections is brought quickly in line with present hospital sector standards.

Will the damage be done before we feel the heat? Infectious disease emergence and human response

The global political economy is facing extreme challenges against a backdrop of large-scale expansion of human and domestic animal populations and related impacts on the biosphere. Significant global socio-ecological changes have occurred in the period of a single lifetime, driven by increased technology and access to physical and biological resources through open markets and globalization. Current resource consumption rates are not sustainable and ecological tipping points are being reached and one of the indicators of these may be a changing balance between hosts and pathogens. A period of extraordinary progress in reducing infection risk and disease impact on humans and domestic animals in the 20th Century is reversing in the 21st, but not always and not everywhere. Drivers for this shift are discussed in terms of demographics, agroecology, biodiversity decline and loss of resilience in ecosystems, climate change and increasing interconnectedness between species globally. Causality of disease emergence remains highly speculative, but patterns and data are emerging to commend a precautionary approach, while reassessing our global political, social and economic systems.

Multiple scales of selection influence the evolutionary emergence of novel pathogens

When pathogens encounter a novel environment, such as a new host species or treatment with an antimicrobial drug, their fitness may be reduced so that adaptation is necessary to avoid extinction. Evolutionary emergence is the process by which new pathogen strains arise in response to such selective pressures. Theoretical studies over the last decade have clarified some determinants of emergence risk, but have neglected the influence of fitness on evolutionary rates and have not accounted for the multiple scales at which pathogens must compete successfully. We present a cross-scale theory for evolutionary emergence, which embeds a mechanistic model of within-host selection into a stochastic model for emergence at the population scale. We explore how fitness landscapes at within-host and between-host scales can interact to influence the probability that a pathogen lineage will emerge successfully. Results show that positive correlations between fitnesses across scales can greatly facilitate emergence, while cross-scale conflicts in selection can lead to evolutionary dead ends. The local genotype space of the initial strain of a pathogen can have disproportionate influence on emergence probability. Our cross-scale model represents a step towards integrating laboratory experiments with field surveillance data to create a rational framework to assess emergence risk.

Increased antibody affinity confers broad in vitro protection against escape mutants of severe acute respiratory syndrome coronavirus

Even though the effect of antibody affinity on neutralization potency is well documented, surprisingly, its impact on neutralization breadth and escape has not been systematically determined. Here, random mutagenesis and DNA shuffling of the single-chain variable fragment of the neutralizing antibody 80R followed by bacterial display screening using anchored periplasmic expression (APEx) were used to generate a number of higher-affinity variants of the severe acute respiratory syndrome coronavirus (SARS-CoV)-neutralizing antibody 80R with equilibrium dissociation constants (K(D)) as low as 37 pM, a >270-fold improvement relative to that of the parental 80R single-chain variable fragment (scFv). As expected, antigen affinity was shown to correlate directly with neutralization potency toward the icUrbani strain of SARS-CoV. Additionally, the highest-affinity antibody fragment displayed 10-fold-increased broad neutralization in vitro and completely protected against several SARS-CoV strains containing substitutions associated with antibody escape. Importantly, higher affinity also led to the suppression of viral escape mutants in vitro. Escape from the highest-affinity variant required reduced selective pressure and multiple substitutions in the binding epitope. Collectively, these results support the hypothesis that engineered antibodies with picomolar dissociation constants for a neutralizing epitope can confer escape-resistant protection.

Agricultural intensification, priming for persistence and the emergence of Nipah virus: a lethal bat-borne zoonosis

Emerging zoonoses threaten global health, yet the processes by which they emerge are complex and poorly understood. Nipah virus (NiV) is an important threat owing to its broad host and geographical range, high case fatality, potential for human-to-human transmission and lack of effective prevention or therapies. Here, we investigate the origin of the first identified outbreak of NiV encephalitis in Malaysia and Singapore. We analyse data on livestock production from the index site (a commercial pig farm in Malaysia) prior to and during the outbreak, on Malaysian agricultural production, and from surveys of NiV's wildlife reservoir (flying foxes). Our analyses suggest that repeated introduction of NiV from wildlife changed infection dynamics in pigs. Initial viral introduction produced an explosive epizootic that drove itself to extinction but primed the population for enzootic persistence upon reintroduction of the virus. The resultant within-farm persistence permitted regional spread and increased the number of human infections. This study refutes an earlier hypothesis that anomalous El Niño Southern Oscillation-related climatic conditions drove emergence and suggests that priming for persistence drove the emergence of a novel zoonotic pathogen. Thus, we provide empirical evidence for a causative mechanism previously proposed as a precursor to widespread infection with H5N1 avian influenza and other emerging pathogens.

Evolution of SARS Coronavirus and the Relevance of Modern Molecular Epidemiology

This chapter discusses the evolution of severe acute respiratory syndrome (SARS) coronavirus and the relevance of modern molecular epidemiology. The first case was reported in China in November 2002 and led to a disastrous worldwide pandemic. An international SARS network was established by WHO to rapidly identify the causative agent. In March 2003, the SARS coronavirus was identified. The majority of the early cases were limited to the Guangdong province of China, which have a unique dietary tradition favoring freshly slaughtered game meat; therefore, studies were conducted in those markets for evidence of SARS-CoV. Antibodies against SARS-CoV were detected in masked palm civets. By using serological and PCR surveillance, it was discovered that SARS-like CoV or SL-CoVs were present in different horseshoe bats in the genus Rhinolophus and that they are the likely natural reservoir hosts of bat SL-CoVs. There are more than 60 different horseshoe species around the world, and one or more of them may serve as the natural reservoir of SARS-CoV and/or its progenitor virus(es). It is therefore likely that another outbreak could occur on a similar scale as that of the SARS-CoV outbreaks but our response to a future outbreak caused by any bat-borne coronavirus will be much more effective. SARS is an example demonstrating the evolution of an animal virus into a human pathogen responsible for one of the most severe global pandemic. It is paramount that from now we include active surveillance of wild animals as part of an integrated infectious disease prevention and control strategy.

Identifying genetic markers of adaptation for surveillance of viral host jumps

Adaptation is often thought to affect the likelihood that a virus will be able to successfully emerge in a new host species. If so, surveillance for genetic markers of adaptation could help to predict the risk of disease emergence. However, adaptation is difficult to distinguish conclusively from the other processes that generate genetic change. In this Review we survey the research on the host jumps of influenza A, severe acute respiratory syndrome-coronavirus, canine parvovirus and Venezuelan equine encephalitis virus to illustrate the insights that can arise from combining genetic surveillance with microbiological experimentation in the context of epidemiological data. We argue that using a multidisciplinary approach for surveillance will provide a better understanding of when adaptations are required for host jumps and thus when predictive genetic markers may be present.

Use of phylogenetics in the molecular epidemiology and evolutionary studies of viral infections

Since DNA sequencing techniques first became available almost 30 years ago, the amount of nucleic acid sequence data has increased enormously. Phylogenetics, which is widely applied to compare and analyze such data, is particularly useful for the analysis of genes from rapidly evolving viruses. It has been used extensively to describe the molecular epidemiology and transmission of the human immunodeficiency virus (HIV), the origins and subsequent evolution of the severe acute respiratory syndrome (SARS)-associated coronavirus (SCoV), and, more recently, the evolving epidemiology of avian influenza as well as seasonal and pandemic human influenza viruses. Recent advances in phylogenetic methods can infer more in-depth information about the patterns of virus emergence, adding to the conventional approaches in viral epidemiology. Examples of this information include estimations (with confidence limits) of the actual time of the origin of a new viral strain or its emergence in a new species, viral recombination and reassortment events, the rate of population size change in a viral epidemic, and how the virus spreads and evolves within a specific population and geographical region. Such sequence-derived information obtained from the phylogenetic tree can assist in the design and implementation of public health and therapeutic interventions. However, application of many of these advanced phylogenetic methods are currently limited to specialized phylogeneticists and statisticians, mainly because of their mathematical basis and their dependence on the use of a large number of computer programs. This review attempts to bridge this gap by presenting conceptual, technical, and practical aspects of applying phylogenetic methods in studies of influenza, HIV, and SCoV. It aims to provide, with minimal mathematics and statistics, a practical overview of how phylogenetic methods can be incorporated into virological studies by clinical and laboratory specialists.

Point-of-care testing and molecular diagnostics: miniaturization required

Turnaround time for molecular diagnostic tests is critical in detecting infectious agents, in determining a patient's ability to metabolize a drug or drug class, and in detecting minimal residual disease. These applications would benefit from the development of a point-of-care device for nucleic acid extraction, amplification, and detection. The ideal device would have a low cost per test, use a disposable unit use device for all steps in the assay, be portable, and provide a result that requires no interpretation. The creation of such a device requires miniaturization of current technologies and the use of microfluidics, microarrays, and small-diameter capillary tubes to reduce reagent volumes and simplify heat conduction by convection during nucleic acid amplification. This ideal device may be available in 3 to 5 years and will revolutionize and expand the global availability of molecular diagnostic assays.

Molecular and Biochemical Characterization of the SARS-CoV Accessory Proteins ORF8a, ORF8b and ORF8ab

A novel coronavirus was identified as the aetiological agent for the global outbreak of severe acute respiratory syndrome (SARS) at the beginning of the twenty-first century. The SARS coronavirus genome encodes for proteins that are common to all members of the coronavirus, i.e. replicase polyproteins (pp1a and pp1b) and structural proteins (spike, membrane, nucleocapsid and envelope), as well as eight accessory proteins. The accessory proteins have been designated as open reading frames (ORF) 3a, 3b, 6, 7a, 7b, 8a, 8b and 9b, and they do not show significant homology to viral proteins of other known coronaviruses. Epidemiological studies have revealed that the part of the viral genome that encodes for ORF8a and ORF8b showed major variations and the animal isolates contain an additional 29-nucleotide sequence which is absent in most of the human isolates. As a result, ORF8a and ORF8b in the human isolates become one ORF, termed ORF8ab. In this chapter, we will discuss the genetic variation in the ORF8 region, expression of ORF8a, ORF8b and ORF8ab during infection, cellular localization and posttranslational modification of ORF8a, ORF8b and ORF8ab, participation of ORF8a, ORF8b and ORF8ab in viral–viral interactions, their effects on other viral proteins and impact on viral replication and/or pathogenesis.

Molecular Pathology and Infectious Diseases

This chapter discusses the pathogenesis and progression of infectious diseases. Agricultural and industrial development has resulted in the increased density of humans living in close proximity to each other. This lifestyle change from more rural existence has brought humans in closer proximity to wild animals that harbor potential future human pathogens. Most diseases are transmitted by insect vectors. Molecular diagnostic tests can be divided into two primary groups. The first are tests designed to detect the presence of mutations in the human genome that are associated with specific diseases. These tests need to be performed only once in a specific individual’s lifetime. The second group of molecular diagnostic assays is designed to detect infectious agents or the recurrence of a mutation specifically associated with a tumor the patient has had in the past. Bacterial, viral, fungal, or parasitic infections can be eradicated and recur at a time in the future requiring repetition of the same molecular assay for detection. Minimal residual disease detection refers to the analysis of tissue/cells in a patient previously diagnosed with a malignancy to evaluate if therapy was completed successfully or if rare malignant cells are present.

Avian influenza virus, Streptococcus suis serotype 2, severe acute respiratory syndrome-coronavirus and beyond: molecular epidemiology, ecology and the situation in China

The outbreak and spread of severe acute respiratory syndrome-associated coronavirus and the subsequent identification of its animal origin study have heightened the world's awareness of animal-borne or zoonotic pathogens. In addition to SARS, the highly pathogenic avian influenza virus (AIV), H5N1, and the lower pathogenicity H9N2 AIV have expanded their host ranges to infect human beings and other mammalian species as well as birds. Even the ‘well-known’ reservoir animals for influenza virus, migratory birds, became victims of the highly pathogenic H5N1 virus. Not only the viruses, but bacteria can also expand their host range: a new disease, streptococcal toxic shock syndrome, caused by human Streptococcus suis serotype 2 infection, has been observed in China with 52 human fatalities in two separate outbreaks (1998 and 2005, respectively). Additionally, enterohaemorrhagic Escherichia coli O157:H7 infection has increased worldwide with severe disease. Several outbreaks and sporadic isolations of this pathogen in China have made it an important target for disease control. A new highly pathogenic variant of porcine reproductive and respiratory syndrome virus (PRRSV) has been isolated in both China and Vietnam recently; although PRRSV is not a zoonotic human pathogen, its severe outbreaks have implications for food safety. All of these pathogens occur in Southeast Asia, including China, with severe consequences; therefore, we discuss the issues in this article by addressing the situation of the zoonotic threat in China.

Phylogenetic perspectives on the epidemiology and origins of SARS and SARS-like coronaviruses

Severe Acute Respiratory Syndrome (SARS) is a respiratory disease caused by a zoonotic coronavirus (CoV) named SARS-CoV (SCoV), which rapidly swept the globe after its emergence in rural China during late 2002. The origins of SCoV have been mysterious and controversial, until the recent discovery of SARS-like CoV (SLCoV) in bats and the proposal of bats as the natural reservior of the Coronaviridae family. In this article, we focused on discussing how phylogenetics contributed to our understanding towards the emergence and transmission of SCoV. We first reviewed the epidemiology of SCoV from a phylogenetic perspective and discussed the controversies over its phylogenetic origins. Then, we summarized the phylogenetic findings in relation to its zoonotic origins and the proposed inter-species viral transmission events. Finally, we also discussed how the discoveries of SCoV and SLCoV expanded our knowledge on the evolution of the Coronaviridae family as well as its implications on the possible future re-emergence of SCoV.

The era of genomic epidemiology

The recent revolution in genomics is already having a profound impact on the practice of epidemiology. The purpose of this commentary is to demonstrate how genomics and epidemiology will continue to rely heavily on each other, now and in the future, by illustrating a number of interaction points between these 2 disciplines: (1) the use of genomics to estimate disease heritability; (2) the impact of genomics on analytical study design; (3) how genome-wide data can be employed to effectively overcome residual population stratification arising from selection bias; (4) the importance of genomics as a tool in epidemiological investigation; (5) the importance of epidemiology in the collection of adequately phenotyped samples for genomics studies, and (6) for unraveling the clinical and therapeutic relevance of genetic variants once they are discovered.

Host Immune Responses to SARS Coronavirus in Humans

The severe acute respiratory syndrome (SARS) is a newly identified infectious disease caused by a novel zoonotic coronavirus (SARS-CoV) with unknown animal reservoirs. The risk of SARS reemergence in humans remains high due to the large animal reservoirs of SARS-CoV-like coronavirus and the genome instability of RNA coronaviruses. An epidemic in 2003 affected more than 8,000 patients in 29 countries, with 10% mortality.

SARS infection is transmitted by air droplets. Clinical and laboratory manifestations include fever, chills, rigor, myalgia, malaise, diarrhea, cough, dyspnoea, pneumonia, lymphopenia, neutrophilia, thrombocytopenia, and elevated serum lactate dehydrogenase, alanine aminotransferase, and creatine kinase activities. Health care workers are a high-risk group, and advanced age is strongly associated with disease severity. Treatment has been empirical, and there is no licensed SARS vaccine for humans so far. However, presence of long-lived neutralizing antibodies and memory T- and B-lymphocytes in convalescent SARS patients raises hope for active immunization. Furthermore, results from preclinical SARS vaccines expressing spike protein to elicit neutralizing antibodies and cellular responses that are protective in mouse and nonhuman primate models are encouraging.

Very little is known of the early events in viral clearance and the onset of innate and inflammatory responses during the SARS infection. Regulation of the innate immune response is associated with the development of adaptive immunity and disease severity in SARS infection. Notably, SARS-CoV has evolved evasive strategies to suppress antiviral type I interferon responses in infected cells. In addition, inflammatory responses are characterized by upregulation of proinflammatory cytokines/chemokines such as IL-6, IP-10, and MCP-1 in tissues and serum, and massive infiltrations of inflammatory cells such as macrophages in infected tissues.

Due to the lack of animal models that mimic the clinical manifestations of human SARS infection for mechanistic study and vaccine evaluation, development of a safe prophylactic SARS vaccine for human use remains a huge challenge. This chapter is written to summarize and highlight the latest clinical, serological, and immunological parameters relevant to the pathogenesis and protective immunity of SARS infection in humans.

Case fatality of SARS in mainland China and associated risk factors

OBJECTIVE

To analyse the case fatality ratio (CFR) and its risk factors for severe acute respiratory syndrome (SARS) in mainland China by using a comprehensive dataset of all probable cases.

METHODS

The data of all probable SARS cases were derived from the Infectious Disease Reporting System of the Center of Diseases Control and Hospital Information Systems, during the 2003 epidemic in mainland China. The definition of probable SARS case was consistent with the definition for clinically confirmed SARS issued by the Ministry of Health of the People's Republic of China. We performed univariate and multivariate logistic regression analysis to determine the association of CFR with age, sex, residence location, occupation, the period of the epidemic and the duration from symptom onset to admission into hospital.

RESULTS

The overall CFR was 6.4% among 5327 probable SARS cases in mainland China. Old age, being a patient during the early period of a local outbreak, and being from Tianjin led to a relatively higher CFR than young age, late stage of a local outbreak and cases from Beijing. Guangdong Province resulted in an even lower CFR compared with Beijing.

CONCLUSIONS

Because of their deteriorated health status and apparent complications, SARS patients aged >60 years had a much higher risk of dying than younger patients. At the early stage of local outbreaks, lack of experience in patient care and perhaps treatment also led to a relatively higher CFR. The Tianjin SARS outbreak happened mainly within a hospital, leading to a high impact of co-morbidity. The relatively young age of the cases partly explains the low CFR in mainland China compared with other countries and areas affected by SARS.

[Application of molecular methods in the diagnosis and epidemiological study of viral respiratory infections]

Hasta la fecha se han identificado más de 200 virus pertenecientes a 6 familias taxonómicas diferentes asociados con la infección del tracto respiratorio humano. La utilización generalizada de métodos moleculares en los laboratorios de microbiología clínica no sólo ha aportado grandes ventajas al diagnóstico de estas infecciones, sino también está permitiendo profundizar en el conocimiento de la enfermedad y el comportamiento epidemiológico de los virus causantes. Esta tecnología incrementa de manera notable el rendimiento de detección de virus en las muestras respiratorias, debido a su elevada sensibilidad en comparación con las técnicas clásicas y a la posibilidad de identificar virus no cultivables o de crecimiento fastidioso en las líneas celulares habituales, lo que permite realizar el diagnóstico etiológico con mayor rapidez. Sin embargo, también comporta algunos inconvenientes, como son detectar virus que se encuentran colonizando la mucosa respiratoria de personas asintomáticas, o en secreciones de pacientes que ya se han recuperado de una infección pasada, a consecuencia de excreción prolongada de éstos. La secuenciación de los productos obtenidos en la reacción de amplificación genómica permite caracterizar de forma adicional los virus detectados mediante su genotipado, realizar estudios de epidemiología molecular e identificar resistencias a determinados antivirales, por citar sólo algunos ejemplos.

T cell responses to whole SARS coronavirus in humans

Effective vaccines should confer long-term protection against future outbreaks of severe acute respiratory syndrome (SARS) caused by a novel zoonotic coronavirus (SARS-CoV) with unknown animal reservoirs. We conducted a cohort study examining multiple parameters of immune responses to SARS-CoV infection, aiming to identify the immune correlates of protection. We used a matrix of overlapping peptides spanning whole SARS-CoV proteome to determine T cell responses from 128 SARS convalescent samples by ex vivo IFN-gamma ELISPOT assays. Approximately 50% of convalescent SARS patients were positive for T cell responses, and 90% possessed strongly neutralizing Abs. Fifty-five novel T cell epitopes were identified, with spike protein dominating total T cell responses. CD8(+) T cell responses were more frequent and of a greater magnitude than CD4(+) T cell responses (p < 0.001). Polychromatic cytometry analysis indicated that the virus-specific T cells from the severe group tended to be a central memory phenotype (CD27(+)/CD45RO(+)) with a significantly higher frequency of polyfunctional CD4(+) T cells producing IFN-gamma, TNF-alpha, and IL-2, and CD8(+) T cells producing IFN-gamma, TNF-alpha, and CD107a (degranulation), as compared with the mild-moderate group. Strong T cell responses correlated significantly (p < 0.05) with higher neutralizing Ab. The serum cytokine profile during acute infection indicated a significant elevation of innate immune responses. Increased Th2 cytokines were observed in patients with fatal infection. Our study provides a roadmap for the immunogenicity of SARS-CoV and types of immune responses that may be responsible for the virus clearance, and should serve as a benchmark for SARS-CoV vaccine design and evaluation.

Cross-species virus transmission and the emergence of new epidemic diseases

Host range is a viral property reflecting natural hosts that are infected either as part of a principal transmission cycle or, less commonly, as "spillover" infections into alternative hosts. Rarely, viruses gain the ability to spread efficiently within a new host that was not previously exposed or susceptible. These transfers involve either increased exposure or the acquisition of variations that allow them to overcome barriers to infection of the new hosts. In these cases, devastating outbreaks can result. Steps involved in transfers of viruses to new hosts include contact between the virus and the host, infection of an initial individual leading to amplification and an outbreak, and the generation within the original or new host of viral variants that have the ability to spread efficiently between individuals in populations of the new host. Here we review what is known about host switching leading to viral emergence from known examples, considering the evolutionary mechanisms, virus-host interactions, host range barriers to infection, and processes that allow efficient host-to-host transmission in the new host population.

Emerging Diseases: Overview

Emerging infectious diseases are diseases that are either new, are newly recognized, or are increasing in prevalence in new areas. Resurgent diseases are also usually grouped in this category, as is antimicrobial resistance. These diseases have been given formal recognition in the past two decades, although a historical outlook demonstrates that the phenomenon has probably been persistent, although largely undetected, through recorded history. Emergence has accelerated recently, driven by factors such as demographic change, land use change, increased rapidity and frequency of intercontinental transportation, and other mostly social trends. Continued infectious disease emergence poses, and will continue to pose, significant challenges for public health and for basic science.

Severe acute respiratory syndrome coronavirus as an agent of emerging and reemerging infection

Before the emergence of severe acute respiratory syndrome (SARS) coronavirus (SARS-CoV) in 2003, only 12 other animal or human coronaviruses were known. The discovery of this virus was soon followed by the discovery of the civet and bat SARS-CoV and the human coronaviruses NL63 and HKU1. Surveillance of coronaviruses in many animal species has increased the number on the list of coronaviruses to at least 36. The explosive nature of the first SARS epidemic, the high mortality, its transient reemergence a year later, and economic disruptions led to a rush on research of the epidemiological, clinical, pathological, immunological, virological, and other basic scientific aspects of the virus and the disease. This research resulted in over 4,000 publications, only some of the most representative works of which could be reviewed in this article. The marked increase in the understanding of the virus and the disease within such a short time has allowed the development of diagnostic tests, animal models, antivirals, vaccines, and epidemiological and infection control measures, which could prove to be useful in randomized control trials if SARS should return. The findings that horseshoe bats are the natural reservoir for SARS-CoV-like virus and that civets are the amplification host highlight the importance of wildlife and biosecurity in farms and wet markets, which can serve as the source and amplification centers for emerging infections.

Synthetic reconstruction of zoonotic and early human severe acute respiratory syndrome coronavirus isolates that produce fatal disease in aged mice

The severe acute respiratory syndrome (SARS) epidemic was characterized by high mortality rates in the elderly. The molecular mechanisms that govern enhanced susceptibility of elderly populations are not known, and robust animal models are needed that recapitulate the increased pathogenic phenotype noted with increasing age. Using synthetic biology and reverse genetics, we describe the construction of a panel of isogenic SARS coronavirus (SARS-CoV) strains bearing variant spike glycoproteins that are representative of zoonotic strains found in palm civets and raccoon dogs, as well as isolates spanning the early, middle, and late phases of the SARS-CoV epidemic. The recombinant viruses replicated efficiently in cell culture and demonstrated variable sensitivities to neutralization with antibodies. The human but not the zoonotic variants replicated efficiently in human airway epithelial cultures, supporting earlier hypotheses that zoonotic isolates are less pathogenic in humans but can evolve into highly pathogenic strains. All viruses replicated efficiently, but none produced clinical disease or death in young animals. In contrast, severe clinical disease, diffuse alveolar damage, hyaline membrane formation, alveolitis, and death were noted in 12-month-old mice inoculated with the palm civet HC/SZ/61/03 strain or early-human-phase GZ02 variants but not with related middle- and late-phase epidemic or raccoon dog strains. This panel of SARS-CoV recombinants bearing zoonotic and human epidemic spike glycoproteins will provide heterologous challenge models for testing vaccine efficacy against zoonotic reintroductions as well as provide the appropriate model system for elucidating the complex virus-host interactions that contribute to more-severe and fatal SARS-CoV disease and acute respiratory distress in the elderly.