Human case of swine influenza A (H1N1) triple reassortant virus infection, Wisconsin

Immunogenicity of chimeric hemagglutinins delivered by an orf virus vector platform against swine influenza virus

Orf virus (ORFV) is a large DNA virus that can harbor and efficiently deliver viral antigens in swine. Here we used ORFV as a vector platform to deliver chimeric hemagglutinins (HA) of Influenza A virus of swine (IAV-S). Vaccine development against IAV-S faces limitations posed by strain-specific immunity and the antigenic diversity of the IAV-S strains circulating in the field. A promising alternative aiming at re-directing immune responses on conserved epitopes of the stalk segment of the hemagglutinin (HA2) has recently emerged. Sequential immunization with chimeric HAs comprising the same stalk but distinct exotic head domains can potentially induce cross-reactive immune responses against conserved epitopes of the HA2 while breaking the immunodominance of the head domain (HA1). Here, we generated two recombinant ORFVs expressing chimeric HAs encoding the stalk region of a contemporary H1N1 IAV-S strain and exotic heads derived from either H6 or H8 subtypes, ORFVΔ121cH6/1 and ORFVΔ121cH8/1, respectively. The resulting recombinant viruses were able to express the heterologous protein in vitro. Further, the immunogenicity and cross-protection of these vaccine candidates were assessed in swine after sequential intramuscular immunization with OV-cH6/1 and OV-cH8/1, and subsequent challenge with divergent IAV-S strains. Humoral responses showed that vaccinated piglets presented increasing IgG responses in sera. Additionally, cross-reactive IgG and IgA antibody responses elicited by immunization were detected in sera and bronchoalveolar lavage (BAL), respectively, by ELISA against different viral clades and a diverse range of contemporary H1N1 IAV-S strains, indicating induction of humoral and mucosal immunity in vaccinated animals. Importantly, viral shedding was reduced in nasal swabs from vaccinated piglets after intranasal challenge with either Oh07 (gamma clade) or Ca09 (npdm clade) IAV-S strains. These results demonstrated the efficiency of ORFV-based vectors in delivering chimeric IAV-S HA-based vaccine candidates and underline the potential use of chimeric-HAs for prevention and control of influenza in swine.

Newly identified lineages of porcine hemagglutinating encephalomyelitis virus exhibit respiratory phenotype

Swine pathogens have a long history of zoonotic transmission to humans, occasionally leading to sustained outbreaks or pandemics. Through a retrospective epidemiological study of swine populations in China, we describe novel lineages of porcine hemagglutinating encephalomyelitis virus (PHEV) complex coronaviruses (CoVs) that cause exclusively respiratory symptoms with no signs of the neurological symptoms typically associated with classical PHEV infection. Through large-scale epidemiological surveillance, we show that these novel lineages have circulated in at least eight provinces in southeastern China. Phylogenetic and recombination analyses of twenty-four genomes identified two major viral lineages causing respiratory symptoms with extensive recombination within them, between them, and between classical PHEV and the novel respiratory variant PHEV (rvPHEV) lineages. Divergence times among the sampled lineages in the PHEV virus complex date back to 1886-1958 (mean estimate 1928), with the two major rvPHEV lineages separating approximately 20 years later. Many rvPHEV viruses show amino acid substitutions at the carbohydrate-binding site of hemagglutinin esterase (HE) and/or have lost the cysteine required for HE dimerization. This resembles the early adaptation of human CoVs, where HE lost its hemagglutination ability to adapt to growth in the human respiratory tract. Our study represents the first report of the evolutionary history of rvPHEV circulating in swine and highlights the importance of characterizing CoV diversity and recombination in swine to identify pathogens with outbreak potential that could threaten swine farming.

Risk factors influencing swine influenza A virus infection in South Korea: A systematic review and meta-analysis of prevalence and seroprevalence

The past and current burden of swine influenza A viruses (swIAV) must be estimated since pigs act as mixing vessels and are considered a potential source of newly emerging IAV variants. The objective of this systematic review and meta-analysis was to integrate data on the prevalence and seroprevalence of swIAV in South Korean domestic pigs and evaluate important risk factors that influence these outcomes. Eight databases were searched for studies that evaluated the prevalence and seroprevalence of swIAV in South Korean pigs using a specified search string; twenty-seven eligible studies were identified after application of a set of pre-determined inclusion criteria by three authors. The reported prevalence and seroprevalence were pooled separately in proportions between 0 and 1, using a random-effect meta-analysis. To identify and quantify potential sources of heterogeneity, subgroup, and meta-regression analyses were conducted using covariates (publication type, swIAV subtype, growth stage of pigs, sampling region, publication year, sampling season, facility, detection method, sample type, and sample size). The overall prevalence and seroprevalence in domestic pigs were 0.05 [95% confidence intervals (CIs): 0.05-0.12] and 0.35 (95% CIs: 0.14-0.63), respectively. To identify the impact of covariates on effect size, a suitable meta-regression model was determined using predictor importance estimates with corrected Akaike information criterion values. Consequently, the best-fit model included two covariates, publication year and sample size, which were significantly associated with high heterogeneity in the subgroup analysis. Furthermore, data visualization depicted a significant non-linear association between swIAV prevalence and seroprevalence and specific growth stages of pigs. These findings suggest that the periodic monitoring of pigs at different growth stages in large farms may help to establish the status of swIAV-spread across species in the region, and thereby minimize pandemic risk.

Immunity and Protective Efficacy of Mannose Conjugated Chitosan-Based Influenza Nanovaccine in Maternal Antibody Positive Pigs

Parenteral administration of killed/inactivated swine influenza A virus (SwIAV) vaccine in weaned piglets provides variable levels of immunity due to the presence of preexisting virus specific maternal derived antibodies (MDA). To overcome the effect of MDA on SwIAV vaccine in piglets, we developed an intranasal deliverable killed SwIAV antigen (KAg) encapsulated chitosan nanoparticles called chitosan-based NPs encapsulating KAg (CS NPs-KAg) vaccine. Further, to target the candidate vaccine to dendritic cells and macrophages which express mannose receptor, we conjugated mannose to chitosan (mCS) and formulated KAg encapsulated mCS nanoparticles called mannosylated chitosan-based NPs encapsulating KAg (mCS NPs-KAg) vaccine. In MDA-positive piglets, prime-boost intranasal inoculation of mCS NPs-KAg vaccine elicited enhanced homologous (H1N2-OH10), heterologous (H1N1-OH7), and heterosubtypic (H3N2-OH4) influenza virus-specific secretory IgA (sIgA) antibody response in nasal passage compared to CS NPs-KAg vaccinates. In vaccinated upon challenged with a heterologous SwIAV H1N1, both mCS NPs-KAg and CS NPs-KAg vaccinates augmented H1N2-OH10, H1N1-OH7, and H3N2-OH4 virus-specific sIgA antibody responses in nasal swab, lung lysate, and bronchoalveolar lavage (BAL) fluid; and IgG antibody levels in lung lysate and BAL fluid samples. Whereas, the multivalent commercial inactivated SwIAV vaccine delivered intramuscularly increased serum IgG antibody response. In mCS NPs-KAg and CS NPs-KAg vaccinates increased H1N2-OH10 but not H1N1-OH7 and H3N2-OH4-specific serum hemagglutination inhibition titers were observed. Additionally, mCS NPs-KAg vaccine increased specific recall lymphocyte proliferation and cytokines IL-4, IL-10, and IFNγ gene expression compared to CS NPs-KAg and commercial SwIAV vaccinates in tracheobronchial lymph nodes. Consistent with the immune response both mCS NPs-KAg and CS NPs-KAg vaccinates cleared the challenge H1N1-OH7 virus load in upper and lower respiratory tract more efficiently when compared to commercial vaccine. The virus clearance was associated with reduced gross lung lesions. Overall, mCS NP-KAg vaccine intranasal immunization in MDA-positive pigs induced a robust cross-reactive immunity and offered protection against influenza virus.

The Impact of COVID-19 on the Insurance Industry

This study investigated the impact of COVID-19 on the insurance industry by studying the case of Ghana from March to June 2020. With a parallel comparison to previous pandemics such as SARS-CoV, H1N1 and MERS, we developed outlines for simulating the impact of the pandemic on the insurance industry. The study used qualitative and quantitative interviews to estimate the impact of the pandemic. Presently, the trend is an economic recession with decreasing profits but increasing claims. Due to the cancellation of travels, events and other economic losses, the Ghanaian insurance industry witnessed a loss currently estimated at GH Ȼ112 million. Our comparison and forecast predicts a normalization of economic indicators from January 2021. In the meantime, while the pandemic persists, insurers should adapt to working from remote locations, train and equip staff to work under social distancing regulations, enhance cybersecurity protocols and simplify claims/premium processing using e-payment channels. It will require the collaboration of the Ghana Ministry of Health, Banking Sector, Police Department, Customs Excise and Preventive Service, other relevant Ministries and the international community to bring the pandemic to a stop.

Origin and Evolution of H1N1/pdm2009: A Codon Usage Perspective

The H1N1/pdm2009 virus is a new triple-reassortant virus. While Eurasian avian-like and triple-reassortant swine influenza viruses are the direct ancestors of H1N1/pdm2009, the classic swine influenza virus facilitate the spectrum of influenza A diversity in pig population when the reassortant events occurred during 1998 to April 2009. The factors that facilitate the final formation of this gene constellation for H1N1/pdm2009 virus from this complex gene pool remain unknown. Since a novel successful virus should efficiently replicate and transmit in their hosts, in this study, we estimated the adaptability of the codon usage patterns of the pool of genes from these lineages of swine influenza viruses to the human expression system. We found that the MP and NA genes of Eurasian avian-like swine influenza viruses, and the PB2, PB1 and PA genes of triple-reassortant swine influenza viruses were best adapted to the human codon usage pattern. As these genes participated in the development of H1N1/pdm2009, they might help in viral replication and strengthen its competitiveness during its emergence. After its emergence in the human population, a gradual optimization of codon usage patterns between 2009 and 2019 to the human codon usage for the H1N1/pdm2009 genes was detected. This reveals that ongoing adaptive evolution, after its original incursion, occurred to further increase the adaptability of overall gene cassette to human expression system.

Characteristics of and Public Health Emergency Responses to COVID-19 and H1N1 Outbreaks: A Case-Comparison Study

BACKGROUND

Recently, the novel coronavirus disease (COVID-19) has already spread rapidly as a global pandemic, just like the H1N1 swine influenza in 2009. Evidences have indicated that the efficiency of emergency response was considered crucial to curb the spread of the emerging infectious disease. However, studies of COVID-19 on this topic are relatively few.

METHODS

A qualitative comparative study was conducted to compare the timeline of emergency responses to H1N1 (2009) and COVID-19, by using a set of six key time nodes selected from international literature. Besides, we also explored the spread speed and peak time of COVID-19 and H1N1 swine influenza by comparing the confirmed cases in the same time interval.

RESULTS

The government's entire emergency responses to the epidemic, H1N1 swine influenza (2009) completed in 28 days, and COVID-19 (2019) completed in 46 days. Emergency responses speed for H1N1 was 18 days faster. As for the epidemic spread speed, the peak time of H1N1 came about 4 weeks later than that of COVID-19, and the H1N1 curve in America was flatter than COVID-19 in China within the first four months after the disease emerged.

CONCLUSIONS

The speed of the emergency responses to H1N1 was faster than COVID-19, which might be an important influential factor for slowing down the arrival of the peak time at the beginning of the epidemic. Although COVID-19 in China is coming to an end, the government should improve the public health emergency system, in order to control the spread of the epidemic and lessen the adverse social effects in possible future outbreaks.

Built-in RNA-mediated chaperone (chaperna) for antigen folding tailored to immunized hosts

High‐quality antibody (Ab) production depends on the availability of immunologically relevant antigens. We present a potentially universal platform for generating soluble antigens from bacterial hosts, tailored to immunized animals for Ab production. A novel RNA‐dependent chaperone, in which the target antigen is genetically fused with an RNA‐interacting domain (RID) docking tag derived from the immunized host, promotes the solubility and robust folding of the target antigen. We selected the N‐terminal tRNA‐binding domain of lysyl‐tRNA synthetase (LysRS) as the RID for fusion with viral proteins and demonstrated the expression of the RID fusion proteins in their soluble and native conformations; immunization predominantly elicited Ab responses to the target antigen, whereas the “self” RID tag remained nonimmunogenic. Differential immunogenicity of the fusion proteins greatly enriched and simplified the screening of hybridoma clones of monoclonal antibodies (mAbs), enabling specific and sensitive serodiagnosis of MERS‐CoV infection. Moreover, mAbs against the consensus influenza hemagglutinin stalk domain enabled a novel assay for trivalent seasonal influenza vaccines. The Fc‐mediated effector function was demonstrated, which could be harnessed for the design of next‐generation “universal” influenza vaccines. The nonimmunogenic built‐in antigen folding module tailored to a repertoire of immunized animal hosts will drive immunochemical diagnostics, therapeutics, and designer vaccines.

Avian influenza viruses in pigs: An overview

This paper reviews important aspects of infection of pigs with avian influenza viruses. Wild waterfowl are the main reservoir for influenza A viruses; other species, such as pigs, can be infected, but most avian strains are imperfectly adapted to replication and transmission in such new hosts. However, some avian-to-porcine host jumps have resulted in the emergence of stable swine influenza virus lineages, with major consequences for both animal and human health. Different categories of factors are involved in these cross-species adaptations, both epidemiological (relating to host-host interactions) and virological (relating to host-virus interactions). An understanding of the adaptation of avian influenza viruses to pigs has benefited from a number of recent studies, but more research is warranted to fully appreciate the key molecular and epidemiological factors involved in this intriguing viral host jump.

Glycosylation of Hemagglutinin and Neuraminidase of Influenza A Virus as Signature for Ecological Spillover and Adaptation among Influenza Reservoirs

Glycosylation of the hemagglutinin (HA) and neuraminidase (NA) of the influenza provides crucial means for immune evasion and viral fitness in a host population. However, the time-dependent dynamics of each glycosylation sites have not been addressed. We monitored the potential N-linked glycosylation (NLG) sites of over 10,000 HA and NA of H1N1 subtype isolated from human, avian, and swine species over the past century. The results show a shift in glycosylation sites as a hallmark of 1918 and 2009 pandemics, and also for the 1976 “abortive pandemic”. Co-segregation of particular glycosylation sites was identified as a characteristic of zoonotic transmission from animal reservoirs, and interestingly, of “reverse zoonosis” of human viruses into swine populations as well. After the 2009 pandemic, recent isolates accrued glycosylation at canonical sites in HA, reflecting gradual seasonal adaptation, and a novel glycosylation in NA as an independent signature for adaptation among humans. Structural predictions indicated a remarkably pleiotropic influence of glycans on multiple HA epitopes for immune evasion, without sacrificing the receptor binding of HA or the activity of NA. The results provided the rationale for establishing the ecological niche of influenza viruses among the reservoir and could be implemented for influenza surveillance and improving pandemic preparedness.

Dynamic Regimes of El Niño Southern Oscillation and Influenza Pandemic Timing

El Niño southern oscillation (ENSO) dynamics has been shown to drive seasonal influenza dynamics. Severe seasonal influenza epidemics and the 2009-2010 pandemic were coincident with chaotic regime of ENSO dynamics. ENSO dynamics from 1876 to 2016 were characterized to determine if influenza pandemics are coupled to chaotic regimes. Time-varying spectra of southern oscillation index (SOI) and sea surface temperature (SST) were compared. SOI and SST were decomposed to components using the algorithm of noise-assisted multivariate empirical mode decomposition. The components were Hilbert transformed to generate instantaneous amplitudes and phases. The trajectories and attractors of components were characterized in polar coordinates and state space. Influenza pandemics were mapped to dynamic regimes of SOI and SST joint recurrence of annual components. State space geometry of El Niños lagged by influenza pandemics were characterized and compared with other El Niños. Timescales of SOI and SST components ranged from sub-annual to multidecadal. The trajectories of SOI and SST components and the joint recurrence of annual components were dissipative toward chaotic attractors. Periodic, quasi-periodic, and chaotic regimes were present in the recurrence of trajectories, but chaos-chaos transitions dominated. Influenza pandemics occurred during chaotic regimes of significantly low transitivity dimension (p < 0.0001). El Niños lagged by influenza pandemics had distinct state space geometry (p < 0.0001). Chaotic dynamics explains the aperiodic timing, and varying duration and strength of El Niños. Coupling of all influenza pandemics of the past 140 years to chaotic regimes of low transitivity indicate that ENSO dynamics drives influenza pandemic dynamics. Forecasts models from ENSO dynamics should compliment surveillance for novel influenza viruses.

Evolutionary ecology of virus emergence

The cross-species transmission of viruses into new host populations, termed virus emergence, is a significant issue in public health, agriculture, wildlife management, and related fields. Virus emergence requires overlap between host populations, alterations in virus genetics to permit infection of new hosts, and adaptation to novel hosts such that between-host transmission is sustainable, all of which are the purview of the fields of ecology and evolution. A firm understanding of the ecology of viruses and how they evolve is required for understanding how and why viruses emerge. In this paper, I address the evolutionary mechanisms of virus emergence and how they relate to virus ecology. I argue that, while virus acquisition of the ability to infect new hosts is not difficult, limited evolutionary trajectories to sustained virus between-host transmission and the combined effects of mutational meltdown, bottlenecking, demographic stochasticity, density dependence, and genetic erosion in ecological sinks limit most emergence events to dead-end spillover infections. Despite the relative rarity of pandemic emerging viruses, the potential of viruses to search evolutionary space and find means to spread epidemically and the consequences of pandemic viruses that do emerge necessitate sustained attention to virus research, surveillance, prophylaxis, and treatment.

Prevalence of Diabetes in the 2009 Influenza A (H1N1) and the Middle East Respiratory Syndrome Coronavirus: A Systematic Review and Meta-Analysis

Over the past two decades a number of severe acute respiratory infection outbreaks such as the 2009 influenza A (H1N1) and the Middle East respiratory syndrome coronavirus (MERS-CoV) have emerged and presented a considerable global public health threat. Epidemiologic evidence suggests that diabetic subjects are more susceptible to these conditions. However, the prevalence of diabetes in H1N1 and MERS-CoV has not been systematically described. The aim of this study is to conduct a systematic review and meta-analysis of published reports documenting the prevalence of diabetes in H1N1 and MERS-CoV and compare its frequency in the two viral conditions. Meta-analysis for the proportions of subjects with diabetes was carried out in 29 studies for H1N1 (n=92,948) and 9 for MERS-CoV (n=308). Average age of H1N1 patients (36.2±6.0 years) was significantly younger than that of subjects with MERS-CoV (54.3±7.4 years, P<0.05). Compared to MERS-CoV patients, subjects with H1N1 exhibited 3-fold lower frequency of cardiovascular diseases and 2- and 4-fold higher prevalence of obesity and immunosuppression, respectively. The overall prevalence of diabetes in H1N1 was 14.6% (95% CI: 12.3-17.0%; P<0.001), a 3.6-fold lower than in MERS-CoV (54.4%; 95% CI: 29.4-79.5; P<0.001). The prevalence of diabetes among H1N1 cases from Asia and North America was ~two-fold higher than those from South America and Europe. The prevalence of diabetes in MERS-CoV cases is higher than in H1N1. Regional comparisons suggest that an etiologic role of diabetes in MERS-CoV may exist distinctive from that in H1N1.

One Health stakeholder and institutional analysis in Kenya

INTRODUCTION

One Health (OH) can be considered a complex emerging policy to resolve health issues at the animal-human and environmental interface. It is expected to drive system changes in terms of new formal and informal institutional and organisational arrangements. This study, using Rift Valley fever (RVF) as a zoonotic problem requiring an OH approach, sought to understand the institutionalisation process at national and subnational levels in an early adopting country, Kenya.

MATERIALS AND METHODS

Social network analysis methodologies were used. Stakeholder roles and relational data were collected at national and subnational levels in 2012. Key informants from stakeholder organisations were interviewed, guided by a checklist. Public sector animal and public health organisations were interviewed first to identify other stakeholders with whom they had financial, information sharing and joint cooperation relationships. Visualisation of the OH social network and relationships were shown in sociograms and mathematical (degree and centrality) characteristics of the network summarised.

RESULTS AND DISCUSSION

Thirty-two and 20 stakeholders relevant to OH were identified at national and subnational levels, respectively. Their roles spanned wildlife, livestock, and public health sectors as well as weather prediction. About 50% of national-level stakeholders had made significant progress on OH institutionalisation to an extent that formal coordination structures (zoonoses disease unit and a technical working group) had been created. However, the process had not trickled down to subnational levels although cross-sectoral and sectoral collaborations were identified. The overall binary social network density for the stakeholders showed that 35 and 21% of the possible ties between the RVF and OH stakeholders existed at national and subnational levels, respectively, while public health actors' collaborations were identified at community/grassroots level. We recommend extending the OH network to include the other 50% stakeholders and fostering of the process at subnational-level building on available cross-sectoral platforms.

Evolutionary patterning of hemagglutinin gene sequence of 2009 H1N1 pandemic

The 2009 H1N1 swine flu is the first pandemic in decades. Infectivity of the influenza virus for human host depends largely on its ability to evade antibodies specific for viral protein called hemagglutinin (HA) that mediates attachment to the host. In the present study we analysed large number of HA gene sequences available in Flu Database maintained at NCBI. Our sequence based analysis clearly demonstrates that the amino acid usage pattern may dramatically change during the course of evolution, and there exists a clear link between a particular pattern of amino acid usage of HA genes and its potential to become infectious. Structural studies revealed how binding efficiency between the HA and sialic acid may alter the pandemic potential of infection. Our work highlights the evolutionary significance and biochemical basis of the selective advantage of certain amino acids of HA in 2009 and provides a link between the characteristics changes in HA protein and their potential to pronounce a global menace to public health.

Characterization of evolutionary changes in hemagglutinin of influenza H1N1 virus: a computational analysis

Influenza virus continues to evolve due to changes in the genome and the new strain of virus is more pathogenic then the previous strain. These changes may also help the virus to cross specie barrier and may also affect the binding pattern of virus.The main theme of the current study is the identification of changes in the hemagglutinin sequence of H1N1 virus from 1960 to 2011 and also how these changes affect the binding properties of virus. From 1960 to 2000 following important changes were observed: Ala198Asp and Gly225Glu in 1980; and Gly225Asp in 1999. From 1999 to 2011 many changes were observed, most of the changes were transient, but two of the changes, Gly225Asp and Ala227Glu, were consistent in the period of 1999-2010. These residues make the binding stronger. The important conserved residues are Asp190, Tyr98, His183 and Gln226. The current study will provide an understanding how virus evolve with the passage of time. The current study also helps to understand the changes in the binding pattern of virus. It will also help for the identification of new therapeutic targets.

One health, multiple challenges: The inter-species transmission of influenza A virus

Influenza A viruses are amongst the most challenging viruses that threaten both human and animal health. Influenza A viruses are unique in many ways. Firstly, they are unique in the diversity of host species that they infect. This includes waterfowl (the original reservoir), terrestrial and aquatic poultry, swine, humans, horses, dog, cats, whales, seals and several other mammalian species. Secondly, they are unique in their capacity to evolve and adapt, following crossing the species barrier, in order to replicate and spread to other individuals within the new species. Finally, they are unique in the frequency of inter-species transmission events that occur. Indeed, the consequences of novel influenza virus strain in an immunologically naïve population can be devastating. The problems that influenza A viruses present for human and animal health are numerous. For example, influenza A viruses in humans represent a major economic and disease burden, whilst the poultry industry has suffered colossal damage due to repeated outbreaks of highly pathogenic avian influenza viruses. This review aims to provide a comprehensive overview of influenza A viruses by shedding light on interspecies virus transmission and summarising the current knowledge regarding how influenza viruses can adapt to a new host.

Swine flu-have we learnt any lesson from the past?

The world has suffered the pandemics due to swine flu in the past. The present epidemic in India has claimed many lives. Even, after the first outbreak of swine flu in 2009 no concrete efforts are done to prevent this infection. There is an urgent need to take radical steps to prevent such epidemics.

Surveillance for emerging respiratory viruses

Several new viral respiratory tract infectious diseases with epidemic potential that threaten global health security have emerged in the past 15 years. In 2003, WHO issued a worldwide alert for an unknown emerging illness, later named severe acute respiratory syndrome (SARS). The disease caused by a novel coronavirus (SARS-CoV) rapidly spread worldwide, causing more than 8000 cases and 800 deaths in more than 30 countries with a substantial economic impact. Since then, we have witnessed the emergence of several other viral respiratory pathogens including influenza viruses (avian influenza H5N1, H7N9, and H10N8; variant influenza A H3N2 virus), human adenovirus-14, and Middle East respiratory syndrome coronavirus (MERS-CoV). In response, various surveillance systems have been developed to monitor the emergence of respiratory-tract infections. These include systems based on identification of syndromes, web-based systems, systems that gather health data from health facilities (such as emergency departments and family doctors), and systems that rely on self-reporting by patients. More effective national, regional, and international surveillance systems are required to enable rapid identification of emerging respiratory epidemics, diseases with epidemic potential, their specific microbial cause, origin, mode of acquisition, and transmission dynamics.

Influenza at the animal–human interface: a review of the literature for virological evidence of human infection with swine or avian influenza viruses other than A(H5N1)

Factors that trigger human infection with animal influenza virus progressing into a pandemic are poorly understood. Within a project developing an evidence-based risk assessment framework for influenza viruses in animals, we conducted a review of the literature for evidence of human infection with animal influenza viruses by diagnostic methods used. The review covering Medline, Embase, SciSearch and CabAbstracts yielded 6,955 articles, of which we retained 89; for influenza A(H5N1) and A(H7N9), the official case counts of the World Health Organization were used. An additional 30 studies were included by scanning the reference lists. Here, we present the findings for confirmed infections with virological evidence. We found reports of 1,419 naturally infected human cases, of which 648 were associated with avian influenza virus (AIV) A(H5N1), 375 with other AIV subtypes, and 396 with swine influenza virus (SIV). Human cases naturally infected with AIV spanned haemagglutinin subtypes H5, H6, H7, H9 and H10. SIV cases were associated with endemic SIV of H1 and H3 subtype descending from North American and Eurasian SIV lineages and various reassortants thereof. Direct exposure to birds or swine was the most likely source of infection for the cases with available information on exposure.

Epidemic status of Swine influenza virus in china

As one of the most significant swine diseases, in recent years, swine influenza (SI) has had an immense impact on public health and has raised extensive public concerns in China. Swine are predisposed to both avian and human influenza virus infections, between that and/or swine influenza viruses, genetic reassortment could occur. This analysis aims at introducing the history of swine influenza virus, the serological epidemiology of swine influenza virus infection, the clinical details of swine influenza, the development of vaccines against swine influenza and controlling the situation of swine influenza in China. Considering the elaborate nature of swine influenza, a more methodical surveillance should be further implemented.

Human infections with influenza A(H3N2) variant virus in the United States, 2011-2012

BACKGROUND. During August 2011-April 2012, 13 human infections with influenza A(H3N2) variant (H3N2v) virus were identified in the United States; 8 occurred in the prior 2 years. This virus differs from previous variant influenza viruses in that it contains the matrix (M) gene from the Influenza A(H1N1)pdm09 pandemic influenza virus. METHODS. A case was defined as a person with laboratory-confirmed H3N2v virus infection. Cases and contacts were interviewed to determine exposure to swine and other animals and to assess potential person-to-person transmission. RESULTS. Median age of cases was 4 years, and 12 of 13 (92%) were children. Pig exposure was identified in 7 (54%) cases. Six of 7 cases with swine exposure (86%) touched pigs, and 1 (14%) was close to pigs without known direct contact. Six cases had no swine exposure, including 2 clusters of suspected person-to-person transmission. All cases had fever; 12 (92%) had respiratory symptoms, and 3 (23%) were hospitalized for influenza. All 13 cases recovered. CONCLUSIONS. H3N2v virus infections were identified at a high rate from August 2011 to April 2012, and cases without swine exposure were identified in influenza-like illness outbreaks, indicating that limited person-to-person transmission likely occurred. Variant influenza viruses rarely result in sustained person-to-person transmission; however, the potential for this H3N2v virus to transmit efficiently is of concern. With minimal preexisting immunity in children and the limited cross-protective effect from seasonal influenza vaccine, the majority of children are susceptible to infection with this novel influenza virus.

Active surveillance for influenza A virus among swine, midwestern United States, 2009-2011

Veterinary diagnostic laboratories identify and characterize influenza A viruses primarily through passive surveillance. However, additional surveillance programs are needed. To meet this need, an active surveillance program was conducted at pig farms throughout the midwestern United States. From June 2009 through December 2011, nasal swab samples were collected monthly from among 540 groups of growing pigs and tested for influenza A virus by real-time reverse transcription PCR. Of 16,170 samples, 746 were positive for influenza A virus; of these, 18.0% were subtype H1N1, 16.0% H1N2, 7.6% H3N2, and 14.5% (H1N1)pdm09. An influenza (H3N2) and (H1N1)pdm09 virus were identified simultaneously in 8 groups. This active influenza A virus surveillance program provided quality data and increased the understanding of the current situation of circulating viruses in the midwestern US pig population.

Surface glycoproteins determine the feature of the 2009 pandemic H1N1 virus

After the outbreak of the swine-origin influenza A H1N1 virus in April 2009, World Health Organization declared this novel H1N1 virus as the first pandemic influenza virus (2009 pH1N1) of the 21st century. To elucidate the characteristics of 2009 pH1N1, the growth properties of A/Korea/01/09 (K/09) was analyzed in cells. Interestingly, the maximal titer of K/09 was higher than that of a seasonal H1N1 virus isolated in Korea 2008 (S/08) though the RNP complex of K/09 was less competent than that of S/08. In addition, the NS1 protein of K/09 was determined as a weak interferon antagonist as compared to that of S/08. Thus, in order to confine genetic determinants of K/09, activities of two major surface glycoproteins were analyzed. Interestingly, K/09 possesses highly reactive NA proteins and weak HA cell-binding avidity. These findings suggest that the surface glycoproteins might be a key factor in the features of 2009 pH1N1.

Replication and immunogenicity of swine, equine, and avian h3 subtype influenza viruses in mice and ferrets

Since it is difficult to predict which influenza virus subtype will cause an influenza pandemic, it is important to prepare influenza virus vaccines against different subtypes and evaluate the safety and immunogenicity of candidate vaccines in preclinical and clinical studies prior to a pandemic. In addition to infecting humans, H3 influenza viruses commonly infect pigs, horses, and avian species. We selected 11 swine, equine, and avian H3 influenza viruses and evaluated their kinetics of replication and ability to induce a broadly cross-reactive antibody response in mice and ferrets. The swine and equine viruses replicated well in the upper respiratory tract of mice. With the exception of one avian virus that replicated poorly in the lower respiratory tract, all of the viruses replicated in mouse lungs. In ferrets, all of the viruses replicated well in the upper respiratory tract, but the equine viruses replicated poorly in the lungs. Extrapulmonary spread was not observed in either mice or ferrets. No single virus elicited antibodies that cross-reacted with viruses from all three animal sources. Avian and equine H3 viruses elicited broadly cross-reactive antibodies against heterologous viruses isolated from the same or other species, but the swine viruses did not. We selected an equine and an avian H3 influenza virus for further development as vaccines.

Human infections with novel reassortant influenza A(H3N2)v viruses, United States, 2011

During July–December 2011, a variant virus, influenza A(H3N2)v, caused 12 human cases of influenza. The virus contained genes originating from swine, avian, and human viruses, including the M gene from influenza A(H1N1)pdm09 virus. Influenza A(H3N2)v viruses were antigenically distinct from seasonal influenza viruses and similar to proposed vaccine virus A/Minnesota/11/2010.

Specific residues in the 2009 H1N1 swine-origin influenza matrix protein influence virion morphology and efficiency of viral spread in vitro

In April 2009, a novel influenza virus emerged as a result of genetic reassortment between two pre-existing swine strains. This highly contagious H1N1 recombinant (pH1N1) contains the same genomic background as North American triple reassortant (TR) viruses except for the NA and M segments which were acquired from the Eurasian swine lineage. Yet, despite their high degree of genetic similarity, we found the morphology of virions produced by the pH1N1 isolate, A/California/04/09 (ACal-04/09), to be predominantly spherical by immunufluorescence and electron microscopy analysis in human lung and swine kidney epithelial cells, whereas TR strains were observed to be mostly filamentous. In addition, nine clinical pH1N1 samples collected from nasal swab specimens showed similar spherical morphology as the ACal-04/09 strain. Sequence analysis between TR and pH1N1 viruses revealed four amino acid differences in the viral matrix protein (M1), a known determinant of influenza morphology, at positions 30, 142, 207, and 209. To test the role of these amino acids in virus morphology, we rescued mutant pH1N1 viruses in which each of the four M1 residues were replaced with the corresponding TR residue. pH1N1 containing substitutions at positions 30, 207 and 209 exhibited a switch to filamentous morphology, indicating a role for these residues in virion morphology. Substitutions at these residues resulted in lower viral titers, reduced growth kinetics, and small plaque phenotypes compared to wild-type, suggesting a correlation between influenza morphology and efficient cell-to-cell spread in vitro. Furthermore, we observed efficient virus-like particle production from cells expressing wild-type pH1N1 M1, but not M1 containing substitutions at positions 30, 207, and 209, or M1 from other strains. These data suggest a direct role for pH1N1 specific M1 residues in the production and release of spherical progeny, which may contribute to the rapid spread of the pandemic virus.

Phylodynamic inference of infectious diseases caused by HIV, enterovirus 71 and the 2009 swine-origin human influenza virus

The rapidly evolving nature of viruses, particularly RNA viruses, exhibit complex phylodynamic behaviors, accumulating mutations across the genome on a timescale observable by humans. Phylodynamic investigations provide unique and quantitative evolutionary data on the origin, progression in terms of time and space, and epidemic and transmission history of pathogens. This review describes recent phylodynamic conjectures on three distinct categories of human viruses, including HIV, enterovirus 71 and the swine-origin pandemic influenza virus H1N1, which are of enormous importance to public health.

Two years after pandemic influenza A/2009/H1N1: what have we learned?

The world had been anticipating another influenza pandemic since the last one in 1968. The pandemic influenza A H1N1 2009 virus (A/2009/H1N1) finally arrived, causing the first pandemic influenza of the new millennium, which has affected over 214 countries and caused over 18,449 deaths. Because of the persistent threat from the A/H5N1 virus since 1997 and the outbreak of the severe acute respiratory syndrome (SARS) coronavirus in 2003, medical and scientific communities have been more prepared in mindset and infrastructure. This preparedness has allowed for rapid and effective research on the epidemiological, clinical, pathological, immunological, virological, and other basic scientific aspects of the disease, with impacts on its control. A PubMed search using the keywords "pandemic influenza virus H1N1 2009" yielded over 2,500 publications, which markedly exceeded the number published on previous pandemics. Only representative works with relevance to clinical microbiology and infectious diseases are reviewed in this article. A significant increase in the understanding of this virus and the disease within such a short amount of time has allowed for the timely development of diagnostic tests, treatments, and preventive measures. These findings could prove useful for future randomized controlled clinical trials and the epidemiological control of future pandemics.

Restored PB1-F2 in the 2009 pandemic H1N1 influenza virus has minimal effects in swine

PB1-F2 is an 87- to 90-amino-acid-long protein expressed by certain influenza A viruses. Previous studies have shown that PB1-F2 contributes to virulence in the mouse model; however, its role in natural hosts-pigs, humans, or birds-remains largely unknown. Outbreaks of domestic pigs infected with the 2009 pandemic H1N1 influenza virus (pH1N1) have been detected worldwide. Unlike previous pandemic strains, pH1N1 viruses do not encode a functional PB1-F2 due to the presence of three stop codons resulting in premature truncation after codon 11. However, pH1N1s have the potential to acquire the full-length form of PB1-F2 through mutation or reassortment. In this study, we assessed whether restoring the full-length PB1-F2 open reading frame (ORF) in the pH1N1 background would have an effect on virus replication and virulence in pigs. Restoring the PB1-F2 ORF resulted in upregulation of viral polymerase activity at early time points in vitro and enhanced virus yields in porcine respiratory explants and in the lungs of infected pigs. There was an increase in the severity of pneumonia in pigs infected with isogenic virus expressing PB1-F2 compared to the wild-type (WT) pH1N1. The extent of microscopic pneumonia correlated with increased pulmonary levels of alpha interferon and interleukin-1β in pigs infected with pH1N1 encoding a functional PB1-F2 but only early in the infection. Together, our results indicate that PB1-F2 in the context of pH1N1 moderately modulates viral replication, lung histopathology, and local cytokine response in pigs.

Epidemiology and clinical presentation of pandemic influenza A (H1N1) among hospitalized children in Kuwait

OBJECTIVE

To describe the epidemiological and clinical characteristics of children hospitalized for the 2009 influenza A H1N1 infection in Kuwait.

MATERIALS AND METHODS

A retrospective chart review of hospitalized children with laboratory-confirmed influenza A H1N1 infection in two hospitals in Kuwait was conducted. Epidemiological characteristics, clinical features, risk factors for severe disease, complications and mortality were analyzed.

RESULTS

The medical records of 197 children hospitalized for the 2009 pandemic H1N1 infection from August 2009 to January 2010 were reviewed. The majority of the children (104; 52.8%) were admitted during the month of October. The median age was 2 years. Most of the admitted children were in two age categories: 64 infants ≤1 year (32%) and 62 schoolchildren >5 years (31%). The most frequent presentations were fever in 193 (98%), cough in 155 (79%) and runny nose in 105 (53%) cases. The majority of the admitted children (109; 55%) had been previously healthy. All children received an antiviral agent (oseltamivir), and antibiotics were administered to 147 (75%). Bacterial co-infections occurred in 3 (1.5%) of all hospitalized children. Six (3%) children were admitted to the intensive care unit, of whom 4 (66%) required artificial ventilation. There was only 1 mortality.

CONCLUSIONS

The pandemic H1N1 infection was associated with a wide spectrum of clinical manifestations. The majority of hospitalized children had previously been healthy. Most of the admitted children had an uncomplicated clinical course.

Swine influenza virus infections in man

Because pigs are susceptible to both avian and human influenza viruses, genetic reassortment between avian, human, and/or swine influenza viruses in the pig host can lead to the generation of novel influenza A viruses (Ma et al. 2009). Since the first serological evidence of a swine influenza virus (SIV) infecting humans in 1958, sporadic cases have continued to occur. In recent years, case reports have been increasing, seemingly in concert with modern pig farming and the emergence of triple reassortant SIVs in swine. SIV infections in man generally are mild or subclinical, and often are not diagnosed; however, SIV infections can be quite serious in patients with underlying medical conditions. As of August 2010, 73 case reports of symptomatic human SIV infections have been documented in the medical literature or reported by health officials (excluding cases of the 2009 pandemic H1N1 influenza virus), of which 7 infections (10 %) resulted in death. While exposure to swine is often considered a risk factor for human SIV infections, 37 of 73 (51 %) reported cases had no known exposure to pigs; consequently, SIV may be crossing the species barrier via transmission routes yet to be acknowledged. In addition, human-to-human transmission was suspected in 10 of 34 (30 %) of the cases with epidemiological investigation. This chapter discusses the observations of illness and infections in humans, risk factors associated with infection, and methods for diagnosing human infections of SIV.

Genetic analysis and antigenic characterization of swine origin influenza viruses isolated from humans in the United States, 1990-2010

Swine influenza viruses (SIV) have been recognized as important pathogens for pigs and occasional human infections with swine origin influenza viruses (SOIV) have been reported. Between 1990 and 2010, a total of twenty seven human cases of SOIV infections have been identified in the United States. Six viruses isolated from 1990 to 1995 were recognized as classical SOIV (cSOIV) A(H1N1). After 1998, twenty-one SOIV recovered from human cases were characterized as triple reassortant (tr_SOIV) inheriting genes from classical swine, avian and human influenza viruses. Of those twenty-one tr_SOIV, thirteen were of A(H1N1), one of A(H1N2), and seven of A(H3N2) subtype. SOIV characterized were antigenically and genetically closely related to the subtypes of influenza viruses circulating in pigs but distinct from contemporary influenza viruses circulating in humans. The diversity of subtypes and genetic lineages in SOIV cases highlights the importance of continued surveillance at the animal-human interface.

The neuropsychiatric aspects of influenza/swine flu: A selective review

The world witnessed the influenza virus during the seasonal epidemics and pandemics. The current strain of H1N1 (swine flu) pandemic is believed to be the legacy of the influenza pandemic (1918-19). The influenza virus has been implicated in many neuropsychiatric disorders. In view of the recent pandemic, it would be interesting to review the neuropsychiatric aspects of influenza, specifically swine flu. Author used popular search engine 'PUBMED' to search for published articles with different MeSH terms using Boolean operator (AND). Among these, a selective review of the published literature was done. Acute manifestations of swine flu varied from behavioral changes, fear of misdiagnosis during outbreak, neurological features like seizures, encephalopathy, encephalitis, transverse myelitis, aseptic meningitis, multiple sclerosis, and Guillian-Barre Syndrome. Among the chronic manifestations, schizophrenia, Parkinson's disease, mood disorder, dementia, and mental retardation have been hypothesized. Further research is required to understand the etiological hypothesis of the chronic manifestations of influenza. The author urges neuroscientists around the world to make use of the current swine flu pandemic as an opportunity for further research.

Cross-reacting antibodies against the pandemic (H1N1) 2009 influenza virus in older Australians

OBJECTIVE

To assess background pre-pandemic cross-reacting antibodies to the pandemic (H1N1) 2009 virus in older populations in Australia.

DESIGN, SETTING AND PARTICIPANTS

Data were opportunistically generated from three cross-sectional pre-pandemic studies involving people aged 60 years or older: a 3-year (2006-2008) study of influenza outbreaks in aged care facilities (ACFs) in Sydney; an investigation of a respiratory virus outbreak in an ACF in rural New South Wales in June 2009; and a non-influenza serosurvey undertaken in NSW in 2007 and 2008.

MAIN OUTCOME MEASURE

Prevalence of pandemic (H1N1) 2009 haemagglutination inhibition (HAI) antibody titres ≥ 1:40 (putative protective level) in pre-pandemic sera.

RESULTS

In total, 259 serum samples from individuals aged 60 years or older (range, 60-101 years) were tested. More than half of the individuals tested were women (151/259; 58.3%). About a third of individuals (37.5%) had cross-reacting HAI antibody titres ≥ 1:40. The prevalence of cross-reacting antibodies was highest in the oldest age groups (≥ 85 years), with more than 60% of these people having HAI antibody titres ≥ 1:40. The proportion of subjects with HAI antibody titres ≥ 1:40 decreased significantly and successively in younger groups to only 12% of those aged 60-64 years.

CONCLUSIONS

Our study suggests a pre-existing influenza A antibody reserve in most of the oldest group of people that was cross-reactive to the new pandemic (H1N1) 2009 virus; this is likely to be lifelong and to have provided them with clinical protection against the first wave of the pandemic. Pandemic influenza control measures need to focus more on younger adults naive to the pandemic virus and at increased risk of severe disease.

Design and performance of the CDC real-time reverse transcriptase PCR swine flu panel for detection of 2009 A (H1N1) pandemic influenza virus

Swine influenza viruses (SIV) have been shown to sporadically infect humans and are infrequently identified by the Influenza Division of the Centers for Disease Control and Prevention (CDC) after being received as unsubtypeable influenza A virus samples. Real-time reverse transcriptase PCR (rRT-PCR) procedures for detection and characterization of North American lineage (N. Am) SIV were developed and implemented at CDC for rapid identification of specimens from cases of suspected infections with SIV. These procedures were utilized in April 2009 for detection of human cases of 2009 A (H1N1) pandemic (pdm) influenza virus infection. Based on genetic sequence data derived from the first two viruses investigated, the previously developed rRT-PCR procedures were optimized to create the CDC rRT-PCR Swine Flu Panel for detection of the 2009 A (H1N1) pdm influenza virus. The analytical sensitivity of the CDC rRT-PCR Swine Flu Panel was shown to be 5 copies of RNA per reaction and 10(-1.3 - -0.7) 50% infectious doses (ID(50)) per reaction for cultured viruses. Cross-reactivity was not observed when testing human clinical specimens or cultured viruses that were positive for human seasonal A (H1N1, H3N2) and B influenza viruses. The CDC rRT-PCR Swine Flu Panel was distributed to public health laboratories in the United States and internationally from April 2009 until June 2010. The CDC rRT-PCR Swine Flu Panel served as an effective tool for timely and specific detection of 2009 A (H1N1) pdm influenza viruses and facilitated subsequent public health response implementation.

The role of swine in the generation of novel influenza viruses

The ecology of influenza A viruses is very complicated involving multiple host species and viral genes. Avian species have variable susceptibility to influenza A viruses with wild aquatic birds being the reservoir for this group of pathogens. Occasionally, influenza A viruses are transmitted to mammals from avian species, which can lead to the development of human pandemic strains by direct or indirect transmission to man. Because swine are also susceptible to infection with avian and human influenza viruses, genetic reassortment between these viruses and/or swine influenza viruses can occur. The potential to generate novel influenza viruses has resulted in swine being labelled 'mixing vessels'. The mixing vessel theory is one mechanism by which unique viruses can be transmitted from an avian reservoir to man. Although swine can generate novel influenza viruses capable of infecting man, at present, it is difficult to predict which viruses, if any, will cause a human pandemic. Clearly, the ecology of influenza A viruses is dynamic and can impact human health, companion animals, as well as the health of livestock and poultry for production of valuable protein commodities. For these reasons, influenza is, and will continue to be, a serious threat to the wellbeing of mankind.

Origins and evolutionary genomics of the novel swine-origin influenza A (H1N1) virus in humans--past and present perspectives

Swine influenza viruses cause annual epidemics and occasional pandemics claiming the lives of millions from the early history up to the present days. This virus has drawn on a bag of evolutionary tricks to survive in one or another form in both humans and pigs with novel gene constellations through the periodic importation or exportation of viral genes. A prime example is emergence of pandemic novel swine-origin influenza A (H1N1) virus (S-OIV) in 2009 that have transmitted to and spread among humans, resulting in outbreaks internationally. The phylogenetic analysis of sequences of all genes of the S-OIV, showed that its genome contained six gene segments that were similar to ones previously found in triple-reassortant swine influenza viruses circulating in pigs in North America. The genes encoding neuraminidase and M protein were most closely related to those in influenza A viruses circulating in swine populations in Eurasia. This unique genetic combination of influenza virus gene segments leading to the emergence of novel S-OIV that had not been seen before in the world. Here, it has been used evolutionary analysis to estimate the timescale of the origins and the early development of the S-OIV epidemic. This paper shows that it was derived from several viruses circulating in swine and makes a briefly review over the origins and evolutionary genomics of current S-OIV in humans with historical perspectives with a view to exhibition of evolutionary relationship between past and present origins of swine influenza viruses.

Receptor specificity of subtype H1 influenza A viruses isolated from swine and humans in the United States

The evolution of classical swine influenza viruses receptor specificity preceding the emergence of the 2009 H1N1 pandemic virus was analyzed in glycan microarrays. Classical swine influenza viruses from the α, β, and γ antigenic clusters isolated between 1945 and 2009 revealed a binding profile very similar to that of 2009 pandemic H1N1 viruses, with selectivity for α2-6-linked sialosides and very limited binding to α2-3 sialosides. Despite considerable genetic divergence, the 'human-like' H1N1 viruses circulating in swine retained strong binding preference for α2-6 sialylated glycans. Interspecies transmission of H1N1 influenza viruses from swine to humans or from humans to swine has not driven selection of viruses with distinct novel receptor binding specificities. Classical swine and human seasonal H1N1 influenza viruses have conserved specificity for similar α2-6-sialoside receptors in spite of long term circulation in separate hosts, suggesting that humans and swine impose analogous selection pressures on the evolution of receptor binding function.

Are there any differences in clinical and laboratory findings on admission between H1N1 positive and negative patients with flu-like symptoms?

Background

The World Health Organization alert for the H1N1 influenza pandemic led to the implementation of certain measures regarding admission of patients with flu-like symptoms. All these instructions were adopted by the Greek National Health System. The aim of this study was to retrospectively examine the characteristics of all subjects admitted to the Unit of Infectious Diseases with symptoms indicating H1N1 infection, and to identify any differences between H1N1 positive or negative patients. Patients from the ED (emergency department) with flu-like symptoms (sore throat, cough, rhinorhea, or nasal congestion) and fever >37.5°C were admitted in the Unit of Infectious diseases and gave pharyngeal or nasopharyngeal swabs. Swabs were tested with real-time reverse-transcriptase-polymerase-chain-reaction (RT-PCR).

Findings

Patients were divided into two groups. Group A comprised 33 H1N1 positive patients and Group B (control group) comprised of 27 H1N1 negative patients. The two groups did not differ in terms of patient age, co-morbidities, length of hospitalization, temperature elevation, hypoxemia, as well as renal and liver function. There were also no significant differences in severity on admission. C-reactive protein (CRP) (mean 12.8 vs. 5.74) and white blood count (WBC) (mean 10.528 vs. 7.114) were significantly higher in group B than in group A upon admission. Obesity was noted in 8 patients of Group A (mean 31.67) and 14 patients of Group B (mean 37.78). Body mass index (BMI) was lower in H1N1 positive than in H1N1 negative patients (mean 31.67 vs. 37.78, respectively; p = 0.009).

Conclusions

The majority of patients in both groups were young male adults. CRP, WBC and BMI were higher among H1N1 negative patients. Finally, clinical course of patients in both groups was mild and uneventful.

Molecular characterization and comparative analysis of pandemic H1N1/2009 strains with co-circulating seasonal H1N1/2009 strains from eastern India

During the peak outbreak (July-September 2009), a total 1886 patients were screened in eastern India, of which 139 (7.37%) and 52 (2.76%) were positive for pH1N1 and seasonal H1N1, respectively. Full-length HA1, NA, NS1 and PB1-F2 genes of representative strains were sequenced. Phylogenetic analysis of deduced amino acid sequences of pH1N1 strains revealed HA1 and NS1 to be of North American swine lineage, and the NA gene of Eurasian swine lineage. Consistent with previous reports, the PB1-F2 gene of pH1N1 strains was unique due to a mutation resulting in a truncated protein of 11 aa. The HA, NA and NS1 genes of H1N1/2009 strains clustered with H1N1 strains of 2000-2009, whereas a subset of strains contained a pH1N1-like truncated PB1-F2. The truncated PB1-F2 may confer the advantage of lower pathogenicity but higher replication and infectivity to the human H1N1 strains. This is the first report of seasonal H1N1/2009 strains with a pH1N1/2009-like gene segment.

2009 H1N1 influenza: a twenty-first century pandemic with roots in the early twentieth century

A swine-origin H1N1 triple-reassortant influenza A virus found to be a distant relative of the 1918 "Spanish flu" virus emerged in April 2009 to give rise to the first influenza pandemic of the 21st century. Although disease was generally mild and similar to seasonal influenza, severe manifestations including respiratory failure were noted in some, particularly those with underlying conditions such as asthma, pregnancy and immunosuppression. Children and younger adults accounted for most cases, hospitalizations and deaths. A reverse transcriptase-polymerase chain reaction assay was superior to antigen-based rapid tests for diagnosis. All 2009 H1N1 pandemic influenza strains were susceptible to 1 or more neuraminidase inhibitors. Monovalent, unadjuvanted 2009 H1N1 vaccines were licensed in the United States in September 2009 and initially targeted to younger individuals, pregnant women, caretakers of infants and healthcare providers. The 2009 H1N1 pandemic highlights the need for modernization of influenza vaccines, improved diagnostics and more rigorous evaluation of mitigation strategies.

Interspecies and intraspecies transmission of influenza A viruses: viral, host and environmental factors

Influenza A viruses are enveloped viruses belonging to the familyOrthomyxoviridaethat encompasses four more genera: Influenza B, Influenza C, Isavirus and Thogotovirus. Type A viruses belong to the only genus that is highly infectious to a variety of mammalian and avian species. They are divided into subtypes based on two surface glycoproteins, the hemagglutinin (HA) and neuraminidase (NA). So far, 16 HA and 9 NA subtypes have been identified worldwide, making a possible combination of 144 subtypes between both proteins. Generally, individual viruses are host-specific, however, interspecies transmission of influenza A viruses is not uncommon. All of the HA and NA subtypes have been isolated from wild birds; however, infections in humans and other mammalian species are limited to a few subtypes. The replication of individual influenza A virus in a specific host is dependent on many factors including, viral proteins, host system and environmental conditions. In this review, the key findings that contribute to the transmission of influenza A viruses amongst different species are summarized.