Seasonal, avian, and novel H1N1 influenza: prevention and treatment modalities

Accounting for cross-immunity can improve forecast accuracy during influenza epidemics

Previous exposure to influenza viruses confers cross-immunity against future infections with related strains. However, this is not always accounted for explicitly in mathematical models used for forecasting during influenza outbreaks. We show that, if an influenza outbreak is due to a strain that is similar to one that has emerged previously, then accounting for cross-immunity explicitly can improve the accuracy of real-time forecasts. To do this, we consider two infectious disease outbreak forecasting models. In the first (the "1-group model"), all individuals are assumed to be identical and cross-immunity is not accounted for. In the second (the "2-group model"), individuals who have previously been infected by a related strain are assumed to be less likely to experience severe disease, and therefore recover more quickly, than immunologically naive individuals. We fit both models to estimated case notification data (including symptomatic individuals as well as laboratory-confirmed cases) from Japan from the 2009 H1N1 influenza pandemic, and then generate synthetic data for a future outbreak by assuming that the 2-group model represents the epidemiology of influenza infections more accurately. We use the 1-group model (as well as the 2-group model for comparison) to generate forecasts that would be obtained in real-time as the future outbreak is ongoing, using parameter values estimated from the 2009 epidemic as informative priors, motivated by the fact that without using prior information from 2009, the forecasts are highly uncertain. In the scenario that we consider, the 1-group model only produces accurate outbreak forecasts once the peak of the epidemic has passed, even when the values of important epidemiological parameters such as the lengths of the mean incubation and infectious periods are known exactly. As a result, it is necessary to use the more epidemiologically realistic 2-group model to generate accurate forecasts. Accounting for cross-immunity driven by exposures in previous outbreaks explicitly is expected to improve the accuracy of epidemiological modelling forecasts during influenza outbreaks.

Bioinformatics design and experimental validation of influenza A virus multi-epitopes that induce neutralizing antibodies

Pandemics caused by influenza A virus (IAV) are responsible for the deaths of millions of humans around the world. One of these pandemics occurred in Mexico in 2009. Despite the impact of IAV on human health, there is no effective vaccine. Gene mutations and translocation of genome segments of different IAV subtypes infecting a single host cell make the development of a universal vaccine difficult. The design of immunogenic peptides using bioinformatics tools could be an interesting strategy to increase the success of vaccines. In this work, we used the predicted amino acid sequences of the neuraminidase (NA) and hemagglutinin (HA) proteins of different IAV subtypes to perform multiple alignments, epitope predictions, molecular dynamics simulations, and experimental validation. Peptide selection was based on the following criteria: promiscuity, protein surface exposure, and the degree of conservation among different medically relevant IAV strains. These peptides were tested using immunological assays to test their ability to induce production of antibodies against IAV. We immunized rabbits and mice and measured the levels of IgG and IgA antibodies in serum samples and nasal washes. Rabbit antibodies against the peptides P11 and P14 (both of which are hybrids of NA and HA) recognized HA from both group 1 (H1, H2, and H5) and group 2 (H3 and H7) IAV and also recognized the purified NA protein from the viral stock (influenza A Puerto Rico/916/34). IgG antibodies from rabbits immunized with P11 and P14 were capable of recognizing viral particles and inhibited virus hemagglutination. Additionally, intranasal immunization of mice with P11 and P14 induced specific IgG and IgA antibodies in serum and nasal mucosa, respectively. Interestingly, the IgG antibodies were found to have neutralizing capability. In conclusion, the peptides designed through in silico studies were validated in experimental assays.

The tree shrew is a promising model for the study of influenza B virus infection

Background

Influenza B virus is a main causative pathogen of annual influenza epidemics, however, research on influenza B virus in general lags behind that on influenza A viruses, one of the important reasons is studies on influenza B viruses in animal models are limited. Here we investigated the tree shrew as a potential model for influenza B virus studies.

Methods

Tree shrews and ferrets were inoculated with either a Yamagata or Victoria lineage influenza B virus. Symptoms including nasal discharge and weight loss were observed. Nasal wash and respiratory tissues were collected at 2, 4 and 6 days post inoculation (DPI). Viral titers were measured in nasal washes and tissues were used for pathological examination and extraction of mRNA for measurement of cytokine expression.

Results

Clinical signs and pathological changes were also evident in the respiratory tracts of tree shrews and ferrets. Although nasal symptoms including sneezing and rhinorrhea were evident in ferrets infected with influenza B virus, tree shrews showed no significant respiratory symptoms, only milder nasal secretions appeared. Weight loss was observed in tree shrews but not ferrets. V0215 and Y12 replicated in all three animal (ferrets, tree shrews and mice) models with peak titers evident on 2DPI. There were no significant differences in peak viral titers in ferrets and tree shrews inoculated with Y12 at 2 and 4DPI, but viral titers were detected at 6DPI in tree shrews. Tree shrews infected with influenza B virus showed similar seroconversion and respiratory tract pathology to ferrets. Elevated levels of cytokines were detected in the tissues isolated from the respiratory tract after infection with either V0215 or Y12 compared to the levels in the uninfected control in both animals. Overall, the tree shrew was sensitive to infection and disease by influenza B virus.

Conclusion

The tree shrew to be a promising model for influenza B virus research.

Electronic supplementary material

The online version of this article (10.1186/s12985-019-1171-3) contains supplementary material, which is available to authorized users.

Zoonotic Influenza and Human Health-Part 2: Clinical Features, Diagnosis, Treatment, and Prevention Strategies

Purpose of Review

Zoonotic influenza viruses are those influenza viruses that cross the animal-human barrier and can cause disease in humans, manifesting from minor respiratory illnesses to multiorgan dysfunction. The increasing incidence of infections caused by these viruses worldwide has necessitated focused attention to improve both diagnostic as well as treatment modalities. In this second part of a two-part review, we discuss the clinical features, diagnostic modalities, and treatment of zoonotic influenza, and provide an overview of prevention strategies.

Recent Findings

Illnesses caused by novel reassortant avian influenza viruses continue to be detected and described; most recently, a human case of avian influenza A(H7N4) has been described from China. We continue to witness increasing rates of A(H7N9) infections, with the latest (fifth) wave, from late 2016 to 2017, being the largest to date. The case fatality rate for A(H7N9) and A(H5N1) infections among humans is much higher than that of seasonal influenza infections. Since the emergence of the A(H1N1) 2009 pandemic, and subsequently A(H7N9), testing and surveillance for novel influenzas have become more effective. Various newer treatment options, including peramivir, favipiravir (T-705), and DAS181, and human or murine monoclonal antibodies have been evaluated in vitro and in animal models.

Summary

Armed with robust diagnostic modalities, antiviral medications, vaccines, and advanced surveillance systems, we are today better prepared to face a new influenza pandemic and to limit the burden of zoonotic influenza than ever before. Sustained efforts and robust research are necessary to efficiently deal with the highly mutagenic zoonotic influenza viruses.

The Chinese prescription lianhuaqingwen capsule exerts anti-influenza activity through the inhibition of viral propagation and impacts immune function

Background

Lianhuaqingwen Capsule (LH-C) is a traditional Chinese medicine (TCM) formula used to treat respiratory tract infectious diseases in Chinese. The aim of this study was to determine the antiviral activity of LH-C and its immunomodulatory effects on viral infection.

Method

The in vitro cytotoxicity and antiviral activity of LH-C was determined by MTT and Plaque reduction assays. Time course study under single-cycle virus growth conditions were used to determine which stage of viral replication was blocked. The effect of LH-C on the nuclear export of the viral nucleoprotein was examined using an indirect immunofluorescence assay. The regulation to different signaling transduction events and cytokine/chemokine expression of LH-C was evaluated using Western blotting and real-time RT-PCR. After virus inoculation, BALB/c mice were administered with LH-C of different concentrations for 5 days. Body-weight, viral titers and lung pathology of the mice were measured, the level of inflammatory cytokines were also examined using real-time RT-PCR.

Results

LH-C inhibited the proliferation of influenza viruses of various strain in vitro, with the 50% inhibitory concentration (IC₅₀) ranging from 0.35 to 2 mg/mL. LH-C blocked the early stages (0–2 h) of virus infection, it also suppressed virus-induced NF-kB activation and alleviated virus-induced gene expression of IL-6, IL-8, TNF-a, IP-10, and MCP-1 in a dose-dependent manner. LH-C treatment efficiently impaired the nuclear export of the viral RNP. A decrease of the viral titers in the lungs of mice were observed in groups administered with LH-C. The level of inflammatory cytokines were also decreased in the early stages of infection.

Conclusions

LH-C, as a TCM prescription, exerts broad-spectrum effects on a series of influenza viruses, including the newly emerged H7N9, and particularly regulates the immune response of virus infection. Thus, LH-C might be a promising option for treating influenza virus infection.

Electronic supplementary material

The online version of this article (doi:10.1186/s12906-017-1585-7) contains supplementary material, which is available to authorized users.

The Chinese prescription lianhuaqingwen capsule exerts anti-influenza activity through the inhibition of viral propagation and impacts immune function

BACKGROUND

Lianhuaqingwen Capsule (LH-C) is a traditional Chinese medicine (TCM) formula used to treat respiratory tract infectious diseases in Chinese. The aim of this study was to determine the antiviral activity of LH-C and its immunomodulatory effects on viral infection.

METHOD

The in vitro cytotoxicity and antiviral activity of LH-C was determined by MTT and Plaque reduction assays. Time course study under single-cycle virus growth conditions were used to determine which stage of viral replication was blocked. The effect of LH-C on the nuclear export of the viral nucleoprotein was examined using an indirect immunofluorescence assay. The regulation to different signaling transduction events and cytokine/chemokine expression of LH-C was evaluated using Western blotting and real-time RT-PCR. After virus inoculation, BALB/c mice were administered with LH-C of different concentrations for 5 days. Body-weight, viral titers and lung pathology of the mice were measured, the level of inflammatory cytokines were also examined using real-time RT-PCR.

RESULTS

LH-C inhibited the proliferation of influenza viruses of various strain in vitro, with the 50% inhibitory concentration (IC50) ranging from 0.35 to 2 mg/mL. LH-C blocked the early stages (0-2 h) of virus infection, it also suppressed virus-induced NF-kB activation and alleviated virus-induced gene expression of IL-6, IL-8, TNF-a, IP-10, and MCP-1 in a dose-dependent manner. LH-C treatment efficiently impaired the nuclear export of the viral RNP. A decrease of the viral titers in the lungs of mice were observed in groups administered with LH-C. The level of inflammatory cytokines were also decreased in the early stages of infection.

CONCLUSIONS

LH-C, as a TCM prescription, exerts broad-spectrum effects on a series of influenza viruses, including the newly emerged H7N9, and particularly regulates the immune response of virus infection. Thus, LH-C might be a promising option for treating influenza virus infection.

Adapting global influenza management strategies to address emerging viruses

Death by respiratory complications from influenza infections continues to be a major global health concern. Antiviral drugs are widely available for therapy and prophylaxis, but viral mutations have resulted in resistance that threatens to reduce the long-term utility of approved antivirals. Vaccination is the best method for controlling influenza, but vaccine strategies are blunted by virus antigenic drift and shift. Genetic shift in particular has led to four pandemics in the last century, which have prompted the development of efficient global surveillance and vaccination programs. Although the influenza pandemic of 2009 emphasized the need for the rapid standardization of global surveillance methods and the preparation and dissemination of global assay standards for improved reporting and diagnostic tools, outbreaks of novel influenza strains continue to occur, and current efforts must be enhanced by aggressive public education programs to promote increased vaccination rates in the global population. Recently, a novel H7N9 avian influenza virus with potential to become a pandemic strain emerged in China and was transmitted from animals to humans with a demonstrated >20% mortality rate. Sporadic outbreaks of highly lethal avian virus strains have already increased public awareness and altered annual vaccine production strategies to prevent the natural adaption of this virus to human-to-human transmission. Additional strategies for combating influenza include advancement of new antivirals for unexploited viral or host cellular targets; novel adjuvants and alternate vaccine delivery systems; and development of universal protein, DNA, or multivalent vaccines designed to increase immune responsiveness and enhance public health response times.

Human monoclonal antibodies broadly neutralizing against influenza B virus

Influenza virus has the ability to evade host immune surveillance through rapid viral genetic drift and reassortment; therefore, it remains a continuous public health threat. The development of vaccines producing broadly reactive antibodies, as well as therapeutic strategies using human neutralizing monoclonal antibodies (HuMAbs) with global reactivity, has been gathering great interest recently. Here, three hybridoma clones producing HuMAbs against influenza B virus, designated 5A7, 3A2 and 10C4, were prepared using peripheral lymphocytes from vaccinated volunteers, and were investigated for broad cross-reactive neutralizing activity. Of these HuMAbs, 3A2 and 10C4, which recognize the readily mutable 190-helix region near the receptor binding site in the hemagglutinin (HA) protein, react only with the Yamagata lineage of influenza B virus. By contrast, HuMAb 5A7 broadly neutralizes influenza B strains that were isolated from 1985 to 2006, belonging to both Yamagata and Victoria lineages. Epitope mapping revealed that 5A7 recognizes 316G, 318C and 321W near the C terminal of HA1, a highly conserved region in influenza B virus. Indeed, no mutations in the amino acid residues of the epitope region were induced, even after the virus was passaged ten times in the presence of HuMAb 5A7. Moreover, 5A7 showed significant therapeutic efficacy in mice, even when it was administered 72 hours post-infection. These results indicate that 5A7 is a promising candidate for developing therapeutics, and provide insight for the development of a universal vaccine against influenza B virus.

Influenza virus is classified into types A, B and C. Influenza A virus is further divided into many subtypes, all of which exist in animals, indicating pandemic potential. By contrast, influenza B virus circulates almost exclusively in humans and, as there is no evidence for reassortment with influenza A virus, there is no indication of pandemic potential. Hence, there is far less accumulated research information regarding influenza B virus than influenza A virus. Influenza B virus, which is classified into two phylogenetic lineages, does, however, cause annual epidemics in humans and is therefore as essential to control as influenza A virus. Recently, the development of a universal vaccine and therapeutic strategies using human monoclonal antibodies (HuMAbs) has been gathering great interest. The present study reports a HuMAb neutralizing a wide range of influenza B viruses of both lineages. This HuMAb recognizes the conserved region of hemagglutinin. Moreover, therapeutic efficacy of this HuMAb was also confirmed by in vivo animal experiments. Thus, this study provides insight for the development of broad-spectrum therapeutics and a universal prophylactic vaccine against influenza B virus.

Immunity toward H1N1 influenza hemagglutinin of historical and contemporary strains suggests protection and vaccine failure

Evolution of H1N1 influenza A outbreaks of the past 100 years is interesting and significantly complex and details of H1N1 genetic drift remains unknown. Here we investigated the clinical characteristics and immune cross-reactivity of significant historical H1N1 strains. We infected ferrets with H1N1 strains from 1943, 1947, 1977, 1986, 1999, and 2009 and showed each produced a unique clinical signature. We found significant cross-reactivity between viruses with similar HA sequences. Interestingly, A/FortMonmouth/1/1947 antisera cross-reacted with A/USSR/90/1977 virus, thought to be a 1947 resurfaced virus. Importantly, our immunological data that didn't show cross-reactivity can be extrapolated to failure of past H1N1 influenza vaccines, ie. 1947, 1986 and 2009. Together, our results help to elucidate H1N1 immuno-genetic alterations that occurred in the past 100 years and immune responses caused by H1N1 evolution. This work will facilitate development of future influenza therapeutics and prophylactics such as influenza vaccines.

Influenza Virus: A Brief Overview

Influenza is a major public health concern, infecting 5-15% of the global population annually. Influenza virus belongs to family Orthomyxoviridae, and has three types A, B and C. Infection by influenza virus A is most common and severe, generally found in humans. It spreads rapidly and affects human population across large geographical region within short period of time with varying degree of pathology from mild to severe. Wild aquatic birds and other animal species like birds, pigs, ferret, horses, seals, whales, mink, giant anteaters, cats and dogs are the reservoir for the influenza A virus. Influenza B and C viruses have very limited host range and appear predominantly in humans. Influenza virus gains pandemic potential through genetic reassortment called "genetic shift" with complete renewal of surface antigen and a small but gradual genetic change by mutations which make it to adapt efficiently in human population called "genetic drift". Although, the epidemiology related to influenza infection has been studied from several years but some facts associated to disease transmission has poorly understood. This article reviews the important aspects of virological, epidemiological and clinical features related to influenza virus for better understanding of disease transmission and its pathogenesis.

Using sentinel surveillance system to monitor seasonal and novel H1N1 influenza infection in Houston, Texas: outcome analysis of 2008-2009 flu season

The advent of the novel H1N1 virus prompted the Houston Department of Health and Human services (HDHHS) to use the existing sentinel surveillance system to effectively monitor the situation of novel H1N1 virus in the Houston metropolitan area. The objective of this study was to evaluate the demographic characteristics and common symptoms associated with confirmed cases of seasonal influenza and Novel H1N1 virus reported to HDHHS between October 2008 and October 2009. A total of 30 providers were randomly selected using the probability proportional to size (PPS) sampling technique to participate in a sentinel surveillance system. The system was used to effectively monitor both seasonal and novel H1N1 virus in the Houston metropolitan area. These providers collected and submitted specimens for testing at HDHHS laboratory from patients with influenza-like illness (ILI) symptoms who visited their clinics during the period, October 2008 and October 2009. These data formed the basis of the current study. Data obtained were subjected to both descriptive and inferential statistical analyses using SAS software version 9.1.3. Overall a total of 1,122 ILI cases were reported to HDHHS by sentinel providers and tested by HDHHS laboratory. Of this number 296 (67.5%) specimens tested positive for influenza A; 140 (32.0%) for influenza B, and 2 (0.46%) for influenza A/B. Two hundred and fifty-nine (59%) were confirmed cases of seasonal influenza and 179 (41%) were novel H1N1 subtype, respectively. The median ages for seasonal influenza and novel H1N1 virus were 7 and 8 years, with majority of the cases reported among children of age 5-9 years. Fever was the most common symptom reported among patients with seasonal flu and novel H1N1 virus, followed by cough. Twenty-three percent (23%) of patients who were vaccinated against seasonal flu prior to the epidemic were infected with seasonal flu virus. The sentinel surveillance system provided timely data on the circulating ILI that assisted in making decisions regarding response activities for both seasonal and novel H1N1 influenza.

Comparative analyses of pandemic H1N1 and seasonal H1N1, H3N2, and influenza B infections depict distinct clinical pictures in ferrets

Influenza A and B infections are a worldwide health concern to both humans and animals. High genetic evolution rates of the influenza virus allow the constant emergence of new strains and cause illness variation. Since human influenza infections are often complicated by secondary factors such as age and underlying medical conditions, strain or subtype specific clinical features are difficult to assess. Here we infected ferrets with 13 currently circulating influenza strains (including strains of pandemic 2009 H1N1 [H1N1pdm] and seasonal A/H1N1, A/H3N2, and B viruses). The clinical parameters were measured daily for 14 days in stable environmental conditions to compare clinical characteristics. We found that H1N1pdm strains had a more severe physiological impact than all season strains where pandemic A/California/07/2009 was the most clinically pathogenic pandemic strain. The most serious illness among seasonal A/H1N1 and A/H3N2 groups was caused by A/Solomon Islands/03/2006 and A/Perth/16/2009, respectively. Among the 13 studied strains, B/Hubei-Wujiagang/158/2009 presented the mildest clinical symptoms. We have also discovered that disease severity (by clinical illness and histopathology) correlated with influenza specific antibody response but not viral replication in the upper respiratory tract. H1N1pdm induced the highest and most rapid antibody response followed by seasonal A/H3N2, seasonal A/H1N1 and seasonal influenza B (with B/Hubei-Wujiagang/158/2009 inducing the weakest response). Our study is the first to compare the clinical features of multiple circulating influenza strains in ferrets. These findings will help to characterize the clinical pictures of specific influenza strains as well as give insights into the development and administration of appropriate influenza therapeutics.

Clinical predictors of novel influenza A (H1N1)infection in Korea

PURPOSE

Pandemic influenza A (H1N1) virus has spread rapidly and prompt diagnosis is needed for successful treatment and prevention of transmission. We investigated clinical predictors, validated the use of previous criteria with laboratory tests, and evaluated the clinical criteria for H1N1 infection in the Korean population.

MATERIALS AND METHODS

We analyzed clinical and laboratory evaluation data from outpatient clinics at Severance Hospital in Seoul, Korea between November 11 and December 5, 2009.

RESULTS

This analysis included a total of 828 patients. Of these, 372 (44.9%) patients were confirmed with H1N1 infection by real-time reverse transcriptase-polymerase chain reaction (RT-PCR). The most common and predictive symptom was cough (90.3%, OR 8.87, 95% CI 5.89- 13.38) and about 40% of H1N1-positive patients were afebrile. The best predictive model of H1N1 infection was cough plus fever or myalgia. The sensitivities, specificities, positive predictive values, and negative predictive values of our suggested criteria were 73.9%, 69.5%, 66.4%, and 76.6%, respectively.

CONCLUSION

Cough was the most common independent symptom in patients with laboratory-confirmed H1N1 infection, and while not perfect, the combination of cough plus fever or myalgia is suggested as clinical diagnostic criteria. Health care providers in Korea should suspect a cough without fever to be an early symptom of H1N1 infection.

Peramivir: An Intravenous Neuraminidase Inhibitor for the Treatment of 2009 H1N1 Influenza

Objective:

To review the efficacy and safety of peramivir, an unapproved neuraminidase inhibitor recently granted an Emergency Use Authorization (EUA) by the Food and Drug Administration (FDA) for the treatment of 2009 H1N1 influenza in select patients.

Data Sources:

Literature was accessed via MEDLINE (1950–April 2010) using the search terms peramivir, BCX-1812, RWJ 270201, influenza H1N1, swine influenza, and neuraminidase inhibitors. The manufacturer of peramivir, BioCryst Pharmaceuticals, was contacted for unpublished data and information presented at recent scientific meetings. Information was obtained from the Centers for Disease Control and Prevention (CDC) and FDA Web sites. The mandatory requirements for the EUA for peramivir were also consulted.

Study Selection and Data Extraction:

Available English-language literature was reviewed and selected based on relevance, as was information from the CDC, FDA, and the drug manufacturer.

Data Synthesis:

The 2009 H1N1 influenza pandemic has necessitated the selective use of intravenous peramivir, an unapproved neuraminidase inhibitor. Intravenous peramivir has been studied in 4 clinical trials, 2 of which compared the drug to oseltamivir. Dose adjustments are required in pediatric patients and in those with impaired renal function. Clinicians wishing to use peramivir must request authorization from the CDC to confirm patient characteristics warranting its use and to verify the prescriber's understanding of dosing considerations and unapproved status.

Conclusions:

Peramivir has shown efficacy for the treatment of 2009 H1N1 influenza; however, it has yet to receive FDA approval. Peramivir is used in hospitalized adult and pediatric patients with suspected or laboratory-confirmed 2009 H1N1 influenza meeting specific criteria, including those unable to receive inhaled or oral neuraminidase inhibitors, those who have not responded to other neuraminidase inhibitors, or when drug delivery by a route other than intravenous is not feasible.

Production of pharmaceutical-grade recombinant aprotinin and a monoclonal antibody product using plant-based transient expression systems

Plants have been proposed as an attractive alternative for pharmaceutical protein production to current mammalian or microbial cell-based systems. Eukaryotic protein processing coupled with reduced production costs and low risk for mammalian pathogen contamination and other impurities have led many to predict that agricultural systems may offer the next wave for pharmaceutical product production. However, for this to become a reality, the quality of products produced at a relevant scale must equal or exceed the predetermined release criteria of identity, purity, potency and safety as required by pharmaceutical regulatory agencies. In this article, the ability of transient plant virus expression systems to produce a wide range of products at high purity and activity is reviewed. The production of different recombinant proteins is described along with comparisons with established standards, including high purity, specific activity and promising preclinical outcomes. Adaptation of transient plant virus systems to large-scale manufacturing formats required development of virus particle and Agrobacterium inoculation methods. One transient plant system case study illustrates the properties of greenhouse and field-produced recombinant aprotinin compared with an US Food and Drug Administration-approved pharmaceutical product and found them to be highly comparable in all properties evaluated. A second transient plant system case study demonstrates a fully functional monoclonal antibody conforming to release specifications. In conclusion, the production capacity of large quantities of recombinant protein offered by transient plant expression systems, coupled with robust downstream purification approaches, offers a promising solution to recombinant protein production that compares favourably to cell-based systems in scale, cost and quality.

A universal long-term flu vaccine may not prevent severe epidemics

BACKGROUND

Recently, the promise of a new universal long-term flu vaccine has become more tangible than ever before. Such a vaccine would protect against very many seasonal and pandemic flu strains for many years, making annual vaccination unnecessary. However, due to complacency behavior, it remains unclear whether the introduction of such vaccines would maintain high and stable levels of vaccination coverage year after year.

FINDINGS

To predict the impact of universal long-term flu vaccines on influenza epidemics we developed a mathematical model that linked human cognition and memory with the transmission dynamics of influenza. Our modeling shows that universal vaccines that provide short-term protection are likely to result in small frequent epidemics, whereas universal vaccines that provide long-term protection are likely to result in severe infrequent epidemics.

CONCLUSIONS

Influenza vaccines that provide short-term protection maintain risk awareness regarding influenza in the population and result in stable vaccination coverage. Vaccines that provide long-term protection could lead to substantial drops in vaccination coverage and should therefore include an annual epidemic risk awareness programs in order to minimize the risk of severe epidemics.

Swine Influenza (H1N1) pneumonia: clinical considerations

Influenza is a viral zoonosis of birds and mammals that has probably existed since antiquity. Attack rates of influenza are relatively high but mortality is relatively low. Influenza mortality is highest in the very young, the very old, and the immunosuppressed. Influenza has the potential for rapid spread and may involve large populations. This article examines the swine influenza (H1N1) strain of recent origin, and compares the microbiology, epidemiology, clinical presentation, differential, clinical, and laboratory diagnosis, therapy, complications, and prognosis with previous recorded outbreaks of avian and human seasonal influenza pneumonias.