New Strain Of Influenza Research Articles

Influenza-associated illness is an important contributor to febrile convulsions in Danish children

To determine the burden of febrile convulsions attributed to influenza like illness in a western country during ten influenza seasons. Based on national Danish registries, we explored the association between influenza like illness (ILI) activity and weekly number of hospital admittances for febrile convulsions in time-series analyses. We included data on 59,870 admissions for febrile convulsions in children between three months and five years of age in the period 1995-2005. There was a significant relation between ILI-activity and number of children admitted for febrile convulsions with a systematic increase in admissions to pediatric wards about one week before the national surveillance system detected the corresponding rise in ILI-activity. The yearly number of admissions attributable to ILI varied from 11 to 47% of admissions and was highest during influenza epidemics. This was in particular observed in seasons when a new strain of influenza A/H3N2 was circulating. During these epidemics, influenza contributed to 29-47% of admissions. Influenza like illness is associated with a considerable burden of febrile convulsions in children, most pronounced in years with epidemics. As febrile convulsions are just one of many complications contributing to the burden of influenza in children, this should be taken into consideration when planning a vaccination strategy for preventing influenza-related morbidity in younger children.

Computational study on new natural polycyclic compounds of H1N1 influenza virus neuraminidase

A new strain of influenza A (H1N1) virus is a major cause of morbidity and mortality around the world. The neuraminidase of the influenza virus has been the most potential target for the anti-influenza drugs such as oseltamivir and zanamivir. However, the emergence of drug-resistant variants of these drugs makes a pressing need for the development of new neuraminidase inhibitors for controlling illness and transmission. Here a 3D structure model of H1N1 avian influenza virus neuraminidase type 1 (N1) was constructed based on the structure of the template H5N1 avian influenza virus N1. Upon application of virtual screening technique for N1 inhibitors, two novel compounds (ZINC database ID: ZINC02128091, ZINC02098378) were found as the most favorable interaction energy with N1. Docking results showed that the compounds bound not only in the active pocket, but also in a new hydrophobic cave which contains Arg368, Trp399, Ile427, Pro431 and Lys432 of N1. Our result suggested that both of the screened compounds containing the hydrophobic group bring a strong conjugation effect with Arg293, Arg368 Lys432 of N1 by pi-pi interaction. However, the control inhibitors zanamivir and oseltamivir do not have this effect. The details of N1-compound binding structure obtained will be valuable for the development of a new anti-influenza virus agent.

The evolution of influenza viruses

Influenza virus infection, one of the most common infectious diseases is a highly contagious airborne disease that causes an acute febrile illness and results invariable degrees of systemic symptoms, ranging from mild fatigue to respiratory failure and death. In addition to humans, influenza also infects a variety of animal species. Influenza A viruses also can infect domestic animals (pigs, horses, dogs, chickens and ducks) and some wild birds. Some of these influenza strains are species specific, but new strains of influenza may spread from other animal species to humans. These deadly strains produced 3 global pandemics in the last century, the worst of which occurred in 1918. Three pandemics of influenza have swept the world since the “Spanish” flu of 1918, the “Asian” flu pandemic of 1957, the “Hong Kong” flu pandemic of 1968, the “Swine” flu pandemic that began in April of 2009. The pandemic of 1957 probably made more people sick than the one of 1918, but the availability of antibiotics to treat the secondary infections that are the usual cause of death resulted in a much lower death rate. An influenza pandemic occurs only when the influenza virus mutates into something dangerously unfamiliar to our immune systems and yet is able to jump from human to human through a sneeze, cough or touch. Asia is the source of many outbreaks because swines, birds and humans live under the same roof, providing opportunity for viral mixing. The best way to prevent the sickness is to get yearly injections of a vaccine that prevents influenza.

Viral respiratory infections during the 2009 influenza A(H1N1) outbreak in the West Midlands Region, UK

In spring 2009 a new strain of influenza A(H1N1) emerged and caused a worldwide pandemic. This study utilized a large collection of respiratory specimens from suspected cases of influenza A(H1N1) in the UK West Midlands during the pandemic in order to investigate which other respiratory viruses were circulating and whether they played any role in the increased hospitalization rates seen during that period. Study specimens were selected from community and hospitalized patients positive and negative for influenza A(H1N1) and tested by PCR for other respiratory viruses. A number of infections diagnosed as influenza during the summer influenza outbreak were found to be due to other virus infections (most commonly rhinovirus). No statistically significant difference was found between the rates of respiratory virus co-infection with H1N1 in patients from community or hospital locations suggesting underlying factors were likely to be more significant than viral co-infections in determining severity of influenza A(H1N1) disease.

Acute Respiratory Distress Syndrome as a presenting manifestation in young patients infected with H1N1 influenza virus

Introduction The new strain of influenza A (H1N1) 2009, often referred to colloquially as “swine flu”, which was first detected in April 2009, raised to a pandemic of which the impact was not completely predictable. As reported, numerous cases with severe respiratory failure were also seen among young previously healthy people. Patients In the present study, we report eight cases of influenza A (H1N1) 2009 admitted to our medical intensive care with severe respiratory failure between November and December 2009 and in January 2011. All patients were older than 30 but younger than 50 years, had clinical and radiological evidence of an Acute Respiratory Distress Syndrome (ARDS) and needed invasive ventilatory support. Results Six of the eight patients had no relevant underlying disease; one had a pre-existing idiopathic lung fibrosis and another had a chronic obstructive pulmonary disease (COPD), an abuse of alcohol and an adiposities grade 3. Four patients needed an extracorporeal membrane oxygenation (ECMO) due to severe respiratory failure with global respiratory insufficiency that could not be treated by conservative ventilatory support. The one patient with a pre-existing lung fibrosis died shortly after lung transplantation despite use of an extracorporeal membrane oxygenation. One other patient died due to a subarachnoidal bleeding under the anticoagulatory regime during ECMO therapy. The adipose COPD-patient died due to septic shock with multiple organ failure without possibility for ECMO support. Conclusions The clinical course of severe cases of influenza A (H1N1) 2009-infection is markedly different from the disease pattern seen during epidemics of seasonal influenza. Most of the patients admitted to our intensive care unit due to influenza A (H1N1) 2009 associated ARDS were previously healthy young people.

Pandemic A/H1N1 influenza: Transmission of the first cases in Spain

Pandemic A/H1N1 influenza emerged in Mexico at the end of March 2009. Since then, it is still important to provide evidences that contributed to the international spread of the virus and to ascertain the attack rate of this new strain of influenza among the first cases in Spain that led to identify the first transmission in Europe. Three pandemic A/H1N1 influenza groups related to an overseas flight were studied: 71 student group, 94 remaining passengers, and 68 contacts of confirmed cases. The attack rate with their 95% confidence interval (CI) among the student group and contacts was calculated. On April 26th, when the first cases were notified, strong preventive measures were implemented among the student group and the contacts of the confirmed cases. On 27th April, the first pandemic A/H1N1 influenza cases confirmed in Spain were three students that came back from Mexico by airplane. A student generated the first native case in Spain and one of the first cases in Europe. Similar attack rates were found between the student group (14.1%; CI: 12.1-16.1) and their contacts (13.2%; CI: 4.4-22.0), but no cases among remaining passengers were detected, suggesting low transmission risk during air travel. The first cases of pandemic A/H1N1 influenza in Spain were imported by airplane from Mexico. Preventive efforts to reduce the impact of the influenza influenced that primary and secondary rates were lower than first estimations by WHO.

Energy Intake and Response to Infection with Influenza

Influenza is a worldwide public health concern, particularly with emerging new strains of influenza to which vaccines are ineffective, limited, or unavailable. In addition, the relationship between adequate nutrition and immune function has been repeatedly demonstrated. Mouse models provide strong evidence that energy extremes, including energy restriction (ER) and diet-induced obesity (DIO), have deleterious effects on the immune response to influenza infection. Both ER and DIO mice demonstrate increased susceptibility and mortality to influenza infection. The effects of ER are more pronounced during innate responses to influenza infection, whereas the effects of DIO are evidenced during innate and adaptive responses to both primary and secondary infection. There are striking similarities between ER and DIO during influenza infection, including impaired natural killer cell function and altered inflammation. Future studies must develop effective nutritional paradigms to offset the effects of these energy extremes on the immune response to an acute infection.

Influenza A/H1N1/2009 virus - experience of the clinical microbiology laboratory of the “L. Sacco” University Hospital in Milan

In the spring of 2009, a new variant of influenza A/H1N1 virus that had never been isolated before, was identified. From April 27 to December 31, 2009 the respiratory samples of 974 patients, obtained from suspected cases of pandemic influenza A virus infection, were analyzed at the Clinical Microbiology Laboratory of the “L. Sacco” University Hospital in Milan. The diagnosis of influenza A/H1N1 infection was performed initially through the use of different molecular biological methods: Seeplex® RV12 ACE Detection (Seegene), NUCLISENS® EASYQ® INFLUENZA A/B (bioMérieux), Influenza A/B Q-PCR Alert (Nanogen) running in parallel with rRT-PCR (CDC) to confirm the positivity to the new influenza virus, then was used a single specific test, Fast set H1N1v (Arrow Diagnostics). Retrospective study of data showed that 293 (30.1%) patients were positive for the new strain of influenza A/H1N1 virus and 8 (0.8%) for influenza A other than H1N1 virus.The distribution of influenza A/H1N1 cases showed two peaks, one on July (62.9%) and the other one on October (36%), moreover we observed that 155 patients (53%) out of 293 positive for influenza A/H1N1 virus aged under 20 years old. The first positivity peak was found in travelers and the second one, occurred 2-3 months prior to the classic seasonal epidemic influenza, was attributed to autochthonous cases , by which the virus had spread worldwide. The highest proportion of cases were among subjects aged from 0 to 20 years and, over this age the positivity rate decreased proportionally with increasing age, in agreement with data reported in other countries.

Physician privacy concerns when disclosing patient data for public health purposes during a pandemic influenza outbreak

BackgroundPrivacy concerns by providers have been a barrier to disclosing patient information for public health purposes. This is the case even for mandated notifiable disease reporting. In the context of a pandemic it has been argued that the public good should supersede an individual's right to privacy. The precise nature of these provider privacy concerns, and whether they are diluted in the context of a pandemic are not known. Our objective was to understand the privacy barriers which could potentially influence family physicians' reporting of patient-level surveillance data to public health agencies during the Fall 2009 pandemic H1N1 influenza outbreak.MethodsThirty seven family doctors participated in a series of five focus groups between October 29-31 2009. They also completed a survey about the data they were willing to disclose to public health units. Descriptive statistics were used to summarize the amount of patient detail the participants were willing to disclose, factors that would facilitate data disclosure, and the consensus on those factors. The analysis of the qualitative data was based on grounded theory.ResultsThe family doctors were reluctant to disclose patient data to public health units. This was due to concerns about the extent to which public health agencies are dependable to protect health information (trusting beliefs), and the possibility of loss due to disclosing health information (risk beliefs). We identified six specific actions that public health units can take which would affect these beliefs, and potentially increase the willingness to disclose patient information for public health purposes.ConclusionsThe uncertainty surrounding a pandemic of a new strain of influenza has not changed the privacy concerns of physicians about disclosing patient data. It is important to address these concerns to ensure reliable reporting during future outbreaks.

Duration of viral shedding in hospitalized patients infected with pandemic H1N1

BackgroundThe first influenza pandemic of the 21th century was ignited by a new strain of influenza A virus (A/H1N1pdm). Specific patient groups, including those with comorbidities, pregnant women, young children, older and immunocompromised patients, are at increased risk for serious influenza-related disease. This study was aimed at investigating the influence of clinical presentation, antiviral treatment and possible drug resistance-associated mutations, on the extent and duration of viral shedding in patients infected with A/H1N1pdm.MethodsAn observational study was performed, based on retrospective review of clinical and laboratory records of patients who were hospitalized for A/H1N1pdm infection at the National Institute for Infectious Diseases "L. Spallanzani", Rome, Italy, between April 24 and December 31, 2009. Among 119 hospitalized patients, 39 were selected for a post hoc analysis, based on the availability of serial nasopharyngeal swabs samples and related information.ResultsEleven out of the 39 study patients (28.2%) presented with pneumonia; 29 (74.4%) received antiviral treatment. Patients with pneumonia were significantly older than patients without pneumonia. The mean values of viral RNA concentration were not significantly increased in patients with pneumonia, but a significant increase in the duration of viral shedding was observed as compared to patients without pneumonia. In patients receiving antivirals, the viral RNA concentration was significantly reduced in comparison to untreated patients at days 4-5 after symptom onset, while the overall duration of viral shedding was only marginally affected. A significant correlation between duration of viral shedding and time elapsed between symptom onset and therapy start was observed, with a significant reduction of days of viral shedding when therapy was initiated within 2 days of symptoms appearance. No known drug resistance mutations were detected in patients with prolonged viral shedding.ConclusionsOur results show that severe respiratory illness is associated with delayed virus clearance in patients with A/H1N1pdm infection. Antivirals caused an early reduction of viral load, but only marginally affected the overall duration of shedding. Prolonged shedding was not associated with the emergence of strains carrying known drug-resistance mutations.

(P1-75) Medical Measurement against Disaster — From the Viewpoint of “Disaster Medicine Compendium”

The world must be resilient against major disasters, whether they are caused by natural hazards or human-related mechanisms. Nowadays, outbreaks of emerging infectious diseases, such as new strains of influenza, are a world wide problem. Special consideration is necessary against chemical, biological, radiological, or nuclear (CBRN) hazards.ResultsThe hardware/mechanical preparedness, measurements of the severe influence in mental/psychological aspects, official public system, incident command system, public education system, and the needs of vulnerable populations should be established prior to a disaster. It is also important to prepare the necessary medical resources. The technical skills needed for triage, emergency care, and appropriate transportation should be trained for.Discussion and ConclusionMeasures should be prepared both from the macroscopic viewpoint as well as microscopic approach. A “Disaster Medicine Compendium” consisting of 20 volumes with more than 5,000 pages, was developed in 2005. Currently, a new version is being prepared.

Retrospective Investigation of an Influenza A/H1N1pdm Outbreak in an Italian Military Ship Cruising in the Mediterranean Sea, May-September 2009

BackgroundClinical surveillance may have underestimated the real extent of the spread of the new strain of influenza A/H1N1, which surfaced in April 2009 originating the first influenza pandemic of the 21st century. Here we report a serological investigation on an influenza A/H1N1pdm outbreak in an Italian military ship while cruising in the Mediterranean Sea (May 24-September 6, 2009).MethodsThe contemporary presence of HAI and CF antibodies was used to retrospectively estimate the extent of influenza A/H1N1pdm spread across the crew members (median age: 29 years).FindingsDuring the cruise, 2 crew members fulfilled the surveillance case definition for influenza, but only one was laboratory confirmed by influenza A/H1N1pdm-specific RT-PCR; 52 reported acute respiratory illness (ARI) episodes, and 183 reported no ARI episodes. Overall, among the 211 crew member for whom a valid serological result was available, 39.3% tested seropositive for influenza A/H1N1pdm. The proportion of seropositives was significantly associated with more crowded living quarters and tended to be higher in those aged <40 and in those reporting ARI or suspected/confirmed influenza A/H1N1pdm compared to the asymptomatic individuals. No association was found with previous seasonal influenza vaccination.ConclusionsThese findings underline the risk for rapid spread of novel strains of influenza A in confined environment, such as military ships, where crowding, rigorous working environment, physiologic stress occur. The high proportion of asymptomatic infections in this ship-borne outbreak supports the concept that serological surveillance in such semi-closed communities is essential to appreciate the real extent of influenza A/H1N1pdm spread and can constitute, since the early stage of a pandemic, an useful model to predict the public health impact of pandemic influenza and to establish proportionate and effective countermeasures.

Scientific Report: Highlights of 24th ICAR, 8–11 May 2011, Sofia, Bulgaria

The 24th ICAR meeting was held in Sofia, Bulgaria, 8-11 May 2011. This report summarizes the presentations by the ICAR award winners, Earl Kern and Brian Gowen; the keynote address by Albert (ADME) Osterhaus; the Plenary lectures by Raina Fichorova, Ralf Bartenschlager and Esteban Domingo; the invited speakers for the symposia; and a few of those by contributors. This report aims to reflect the diversity of topics across different disciplines (chemistry to biology) discussed at ICAR: old viruses (smallpox), emerging viruses (SARS, new strains of influenza and flaviviruses), problematic viruses (HIV and HCV), sporadic viruses (arenaviruses), neglected viruses (enteroviruses), new research targets (for HCV) and new approaches (lethal mutagenesis). There were timely reports on promising compounds against adenoviruses, cytomegalovirus, HCV and HIV in clinical trials.This conference illuminated the constantly evolving field of antiviral chemotherapy by providing a forum to present and discuss new antiviral compounds, new uses for old compounds and exciting clinical results. This ICAR was a fitting testament to the 'father of antiviral chemotherapy', Bill Prusoff, who died aged 90 in April 2011.

Novel Swine Infl uenza AH1N1 and the Phase Six Pandemic

The family Orthomyxoviridae consists of Influenza A virus which is negative sense single stranded virus. The genome of the virus is segmented and possesses a peculiar trait of genetic reassortment. The influenza virus on its envelop consists of the antigenic glycoprotein like haemagglutinin (HA) and neuraminidase (NA). The changes in those glycoprotein components due to antigenic shift and antigenic drift leads to the development of new strain of Influenza A viruses. Now the novel swine influenza A/H1N1 strain has been detected from different parts of the world which is causing pandemic. World Health Organization has declared the pandemic phase six and more than 60 countries have reported the cases of novel influenza A/H1N1 strain including Nepal. As the disease is spreading world wide, it is a major public health concern for all the countries. And especially the developing countries like Nepal should immediately respond to the situation and should be well prepared to combat the disease before the disease spreads to enough population.

Amino acid sequence analysis and identification of mutations under positive selection in hemagglutinin of 2009 influenza A (H1N1) isolates

The 2009 flu pandemic is caused by a new strain of influenza A (H1N1) virus, A/H1N1/09. With its high transmissibility, this novel virus has caused a pandemic and infected over 600,000 people globally. By comparing the hemagglutinin (HA) gene and protein sequences among over 700 A/H1N1/09 isolates, mutations in the receptor-binding sites and antigenic epitope regions were identified. Among these mutations, T220 and E/G239 were found to be strongly positively selected over the course of spreading of the A/H1N1/09 virus worldwide. Interestingly, both sites are located in the highly variable epitope regions of HA1, and residue 239 also plays an important role in the receptor-binding process. Further analyses demonstrated that the percentage of T220 mutants among all isolates increased rapidly during the evolution, and that an E/G239 mutation could decrease the binding affinity of the virus with its cellular receptor. Thus, due to a potential functional importance of residues 220 and 239, mutations at these sites, as well as the significant of positive selection on these sites deserves more attention, while new vaccines and therapeutic drugs are developed against this novel virus.

Structure function studies on different structural domains of nucleoprotein of H1N1 subtype

Recent 2009 flu pandemic is a global outbreak of a new strain of influenza A virus subtype H1N1. The H1N1 virus has crossed species barrier to human and apparently acquired the capability to transmit this disease from human to human. The NP is a multifunctional protein that not only encapsidates viral RNA (vRNA), but also forms homo-oligomer and thereby maintains RNP structure. It is also thought to be the key adaptor for virus and host cell interaction. Thus, it is one of the factor that play a key role in the pathogenesis of influenza A virus infection. Therefore, to understand the cause of pathogenicity of H1N1 virus, we have studied the structure-function relationship of different domains of NP. Our results showed that conservative mutation in NP of various strains were pathogenic in nature. However, non-conservative mutation slightly abrogated oligomerization and was therefore less pathogenic. Our results also suggest that beside tail and body domain, head domain may also participate in an oligomerization process.

Mapping the risk of avian influenza in wild birds in the US.

BackgroundAvian influenza virus (AIV) is an important public health issue because pandemic influenza viruses in people have contained genes from viruses that infect birds. The H5 and H7 AIV subtypes have periodically mutated from low pathogenicity to high pathogenicity form. Analysis of the geographic distribution of AIV can identify areas where reassortment events might occur and how high pathogenicity influenza might travel if it enters wild bird populations in the US. Modelling the number of AIV cases is important because the rate of co-infection with multiple AIV subtypes increases with the number of cases and co-infection is the source of reassortment events that give rise to new strains of influenza, which occurred before the 1968 pandemic. Aquatic birds in the orders Anseriformes and Charadriiformes have been recognized as reservoirs of AIV since the 1970s. However, little is known about influenza prevalence in terrestrial birds in the order Passeriformes. Since passerines share the same habitat as poultry, they may be more effective transmitters of the disease to humans than aquatic birds. We analyze 152 passerine species including the American Robin (Turdus migratorius) and Swainson's Thrush (Catharus ustulatus).MethodsWe formulate a regression model to predict AIV cases throughout the US at the county scale as a function of 12 environmental variables, sampling effort, and proximity to other counties with influenza outbreaks. Our analysis did not distinguish between types of influenza, including low or highly pathogenic forms.ResultsAnalysis of 13,046 cloacal samples collected from 225 bird species in 41 US states between 2005 and 2008 indicates that the average prevalence of influenza in passerines is greater than the prevalence in eight other avian orders. Our regression model identifies the Great Plains and the Pacific Northwest as high-risk areas for AIV. Highly significant predictors of AIV include the amount of harvested cropland and the first day of the year when a county is snow free.ConclusionsAlthough the prevalence of influenza in waterfowl has long been appreciated, we show that 22 species of song birds and perching birds (order Passeriformes) are influenza reservoirs in the contiguous US.

2009 H1N1 Influenza Pandemic

The 2009 H1N1 influenza pandemic took health care workers worldwide by surprise. Early in the course of the pandemic it was determined that children and pregnant women were at high risk of increased morbidity and mortality from the novel influenza virus. The Centers for Disease Control and Prevention and state and local public health officials quickly rallied to develop treatment guidelines for the new strain of influenza A, including emergency approvals for off-label use of some antiviral drugs. Prevention of the spread of influenza via vaccination and environmental controls is critical to the health of children. The 2009 H1N1 influenza virus emerged too late to be included in the 2009/2010 seasonal influenza vaccine, so production of a monovalent vaccine was set in motion. Five months from when the first cases of novel H1N1 appeared in Mexico and the United States, a vaccine was being distributed to high-risk patients. Looking ahead to the 2010/2011 influenza season, it is difficult to predict 2009 H1N1 activity. The 2010/2011 seasonal influenza vaccine will include the 2009 H1N1 strain, so it is critical to get all children vaccinated early in the flu season.

H1N1 09 influenza—An aeromedical perspective

The Royal Flying Doctor Service, Queensland Section is the primary service provider for aeromedical retrieval and transfer within Queensland. During the recent H1N1 09 influenza pandemic the organisation was required to undertake substantial planning as well as revision of existing guidelines in light of a new strain of influenza of unknown transmissibility and virulence and potential increase in workload. This paper provides an overview of the experiences of the organisation during the H1N1 09 influenza pandemic including surge capacity planning, infection control measures unique to the aeromedical environment, caseload data and employee health impacts. The Royal Flying Doctor Service, Queensland Section is the primary service provider for aeromedical retrieval and transfer within Queensland. During the recent H1N1 09 influenza pandemic the organisation was required to undertake substantial planning as well as revision of existing guidelines in light of a new strain of influenza of unknown transmissibility and virulence and potential increase in workload. This paper provides an overview of the experiences of the organisation during the H1N1 09 influenza pandemic including surge capacity planning, infection control measures unique to the aeromedical environment, caseload data and employee health impacts.

In Silico Identification of the Potential Drug Resistance Sites over 2009 Influenza A (H1N1) Virus Neuraminidase

The outbreak and high speed global spread of the new strain of influenza A (H1N1) virus in 2009 poses a serious threat to the general population and governments. At present, the most effective drugs for the treatment of 2009 influenza A (H1N1) virus are neuraminidase inhibitors: mainly oseltamivir and zanamivir. The use of these two inhibitors will undoubtedly increase, and therefore it is more likely that drug-resistant influenza strains will arise. The identification of the potential resistance sites for these drugs in advance and the understanding of corresponding molecular basis to cause drug resistance are no doubt very important to fight against the new resistant influenza strains. In this study, first, the complexes of neuraminidase with the substrate sialic acid and two inhibitors oseltamivir and zanamivir were obtained by fitting them to the 3D structure of 2009 influenza A (H1N1) neuraminidase obtained by homology modeling. By using these complexes as the initial structures, molecular dynamics simulation and molecular mechanics generalized Born surface area (MM-GBSA) calculations were performed to identify the residues with significant contribution to the binding of substrate and inhibitors. By analyzing the difference of interaction profiles of substrate and inhibitors, the potential drug resistance sites for two inhibitors were identified. Parts of the identified sites have been verified to confer resistance to oseltamivir and zanamivir for influenza virus of the past flu epidemic. The identified potential resistance sites in this study will be useful for the development of new effective drugs against the drug resistance and avoid the situation of having no effective drugs to treat new mutant influenza strains.