Sixty-two severe and critical patients with 2009 influenza A （H1N1） in Shanghai, China

Background Pandemic influenza A （H1N1） emerged rapidly in China in May 2009. Preliminary comparisons with seasonal influenza suggest that pandemic 2009 influenza A （HIN1） disproportionately affects younger ages and causes generally mild disease. To characterize disease progress, comorbidities, and treatment outcomes among consecutive severe and critically ill patients in a hospital served as a reference center for the care of patients with HIN1 in Shanghai, China.Methods A retrospective study on 62 severe and critically ill patients with 2009 influenza A （H1N1） was conducted in Shanghai Public Health Clinical Center. Demographic data, symptoms, comorbidities, disease progression, treatments, and clinical outcomes were collected for analysis.

Novel H1N1 influenza A virus infection in a patient with acute rejection after liver transplantation

BACKGROUND:The 2009 H1N1 influenza A virus was first identified in April 2009 and rapidly evolved into a pandemic. Recipients of solid-organ transplants have a higher risk for severe infection because of immunosuppression.There are limited reports of 2009 H1N1 influenza in liver transplant recipients,especially in China. METHODS:We present a case of a 48-year-old male liver transplant recipient with 2009 H1N1 influenza A virus.He received therapy for acute rejection after transplantation and was confirmed with H1N1 virus infection. RESULTS:The patient was started on oseltamivir(75 mg, orally twice daily)and had a benign hospital course,with defervescence and resolution of symptoms within 72 hours. The follow-up chest radiograph after discharge was normal. CONCLUSIONS:The 2009 H1N1 influenza in this hospitalized transplant recipient was relatively mild,and prolonged viral shedding was not noted.Oseltamivir can be a valid measure in immunocompromised individuals.

Traditional Chinese medicine as monotherapy or combined with oseltamivir in the treatment of H1N1 influenza:a systematic review and meta-analysis

Objective This study aimed to assess the efficacy and safety of traditional Chinese medicine,alone or in combination with oseltamivir,in patients with H1N1 Influenza.Methods In the present study,we searched the Cochrane Central Register of Controlled Trials,PUBMED,EMBASE,Chinese Biomedical Literature Database,China Science and Technology Journal Database,China National Knowledge Infrastructure Database,and WanFang Data for studies published in or before February 8,2022.Data were extracted and checked by two investigators.Review Manager 5.4 and STATA statistical software 16.0 were used for the data analysis.Results We identified 22 individual studies reporting data from 2292 individuals with H1N1 influenza.Compared with oseltamivir,the fever clearance duration[MD=-3.99,95%CI(-6.89,-1.09)]and sore throat relief time[MD=-5.39,95%CI(-10.19,-0.59)]in the intervention group of traditional Chinese medicine monotherapy or combined with oseltamivir were shorter.Maxingshigan was the primary component of Lianhuaqingwen.The subgroup analyses indicated that Maxingshigan shortened fever clearance time[MD=-3.23,95%CI(-5.60,-0.85)],and also had certain advantages in relieving sore throat[RR=-4.55,95%CI(-10.04,0.95)].However,as for the effective rate,fever duration,cough disappearance time,hospital length of stay,clinical symptoms time as well as viral shedding duration,there were no significant differences between the two groups.Besides,no serious adverse effects were reported in the included studies.Conclusion Although we couldn’t get a definitive conclusion due to the small sample sizes and high risk of bias in the included studies,most traditional Chinese medicine showed similar effects to oseltamivir in treating H1N1 influenza.Some were showed to have a statistically significant shorter time of fever clearance and sore throat remission when they were used alone or in combination with oseltamivir and were well-tolerated treatment,such as Maxingshigan.

The interaction between the 2009 H1N1 influenza A hemagglutinin and neuraminidase: mutations, co-mutations, and the NA stalk motifs

As the world is closely watching the current 2009 H1N1 pandemic unfold, there is a great interest and need in understanding its origin, genetic structures, virulence, and pathogenicity. The two surface proteins, hemagglutinin (HA) and neuraminidase (NA), of the influenza virus have been the focus of most flu research due to their crucial biological functions. In our previous study on 2009 H1N1, three aspects of NA were investigated: the mutations and co-mutations, the stalk motifs, and the phylogenetic analysis. In this study, we turned our attention to HA and the interaction between HA and NA. The 118 mutations of 2009 H1N1 HA were found and mapped to the 3D homology model of H1, and the mutations on the five epitope regions on H1 were identified. This information is essential for developing new drugs and vaccine. The distinct response patterns of HA to the changes of NA stalk motifs were discovered, illustrating the functional dependence between HA and NA. With help from our previous results, two co-mutation networks were uncovered, one in HA and one in NA, where each mutation in one network co-mutates with the mutations in the other network across the two proteins HA and NA. These two networks residing in HA and NA separately may provide a functional linkage between the mutations that can impact the drug binding sites in NA and those that can affect the host immune response or vaccine efficacy in HA. Our findings demonstrated the value of conducting timely analysis on the 2009 H1N1 virus and of the integrated approach to studying both surface proteins HA and NA together to reveal their interdependence, which could not be accomplished by studying them individually.

Gene Expression Profiles Comparison between 2009 Pandemic and Seasonal H1N1 Influenza Viruses in A549 Cells

Objective To perform gene expression profiles comparison so that to identify and understand the potential differences in pathogenesis between the pandemic and seasonal A （H1N1） influenza viruses. Methods A549 cells were infected with A/California/07/09 （H1N1） and A/GuangdongBaoan/51/08 （H1N1） respectively at the same MOI of 2 and collected at 2, 4, 8, and 24 h post infection （p.i.）. Gene expression profiles of A549 cells were obtained using the 22 K Human Genome Oligo Array, and differentially expressed genes were analyzed at selected time points. Results Microarrays results indicated that both of the viruses suppressed host immune response related pathways including cytokine production while pandemic H1N1 virus displayed weaker suppression of host immune response than seasonal H1N1 virus. Observation on similar anti-apoptotic events such as activation of apoptosis inhibitor and down-regulation of key genes of apoptosis pathways in both infections showed that activities of promoting apoptosis were different in later stage of infection. Conclusion The immuno-suppression and anti-apoptosis events of pandemic H1N1 virus were similar to those seen by seasonal H1N1 virus. The pandemic H1N1 virus had an ability to inhibit biological pathways associated with cytokine responses, NK activation and macrophage recognition .

Subtle differences in receptor binding specificity and gene sequences of the 2009 pandemic H1N1 influenza virus

A recent phylogenetic inference indicated that the 2009 pandemic H1N1 strains circulating from March 2009 to September 2009 could be divided into two closely related but distinct clusters. Cluster one contained most strains from Mexico, Texas, and California, and cluster two had most strains from New York, both of which were reported to co-circulate in all continents. The same study further revealed nine nucleotide changes in six gene segments of the new virus specific for the two clusters. In the current study, the informational spectrum method (ISM), a bioinformatics technique, was employed to study the receptor binding patterns of the two clusters. It discovered that while both groups shared the same primary human binding affinity, their secondary binding preferences were different. Cluster one favored swine binding as its secondary binding pattern, whereas cluster two mostly exhibited the binding specificity of A/South Carolina/1/18 (H1N1) (one of the 1918 flu pandemic strains) as its secondary binding pattern. Besides all the nine nucleotide changes found in the previous study, Random Forests were applied to uncover several new nucleotide polymorphisms in 10 genes of the strains between the two clusters, and several amino acid changes in the HA protein that might be accountable for the discrepancy of the secondary receptor binding patterns of the two clusters. Finally, entropy analysis was conducted to present a global view of gene sequence variations between the two clusters, which illustrated that cluster one had much higher genetic divergence than cluster two. Furthermore, it suggested a significant overall correspondence between the nucleotide positions of high importance in differentiating the two clusters and nucleotide positions of high entropy in cluster one.

Clinical Characteristics of H1N1 Influenza A-Associated Mild Encephalopathy with Reversible Splenial Lesion: 4 Pediatric Cases

Objective Mild encephalopathy with reversible splenial lesion(MERS)is associated with a variety of infections and anti-epileptic drug withdrawal.Here we report the clinical characteristics of H1N1 influenza A-associated MERS based on our experience of four pediatric cases.Methods A detailed retrospective analysis of four patients with H1N1 influenza A-associated MERS was performed at Guangzhou Women and Children’s Medical Center.Results All patients exhibited mild influenza-like illness and seizures.Three patients presented with a new-onset seizure with fever after 5 years of age.75%patients had altered mental status.For all four patients,influenza A(H1N1)viral RNA was detected in throat swab specimens at least twice.Brain magnetic resonance images revealed similar ovoid lesions in the corpus callosum,mainly in the splenium and for one patient in the splenium and genu of the corpus callosum.Only one patient had an abnormal electroencephalogram tracing.Cells and protein in the cerebrospinal fluid were normal in all patients.All patients received oseltamivir and one patient received intravenous immunoglobulin.As a result,all patients fully recovered after 2 months and showed no neurologic sequelae at discharge.Conclusion This case series provides insight towards clinical features of H1N1 influenza A-associated MERS.

Intergenic subset organization within a set of geographically-defined viral sequences from the 2009 H1N1 influenza A pandemic

We report a bioinformatic analysis of the datasets of sequences of all ten genes from the 2009 H1N1 influenza A pandemic in the state of Wisconsin. The gene with the greatest summed information entropy was found to be the hemagglutinin (HA) gene. Based upon the viral ID identifier of the HA gene sequence, the sequences of all of the genes were sorted into two subsets, depending upon whether the nucleotide occupying the position of maximum entropy, position 658 of the HA sequence, was either A or U. It was found that the information entropy (H) distributions of subsets differed significantly from each other, from H distributions of randomly generated subsets and from the H distributions of the complete datasets of each gene. Mutual information (MI) values facilitated identification of nine nucleotide positions, distributed over seven of the influenza genes, at which the nucleotide subsets were disjoint, or almost disjoint. Nucleotide frequencies at these nine positions were used to compute mutual information values that subsequently served as weighting factors for edges in a graph net-work. Seven of the nucleotide positions in the graph network are sites of synonymous mutations. Three of these sites of synonymous mutation are within a single gene, the M1 gene, which occupied the position of greatest graph centrality. It is proposed that these bioinformatic and network graph results may reflect alterations in M1-mediated viral packaging and exteriorization, known to be susceptible to synonymous mutations.

Screening of Potent Inhibitor of H1N1 Influenza NS1 CPSF30 Binding Pocket by Molecular Docking

The swine flu, H1N1 virus was outbroken in Mexico and the United States in April 2009 and then rapidly spread worldwide. The World Health Organization declared that the outbreak of influenza is caused by a new subtype of influenza H1N1 influenza virus. And researchers have isolated some oseltamivir resistance strains in 2009 swine flu which makes the imminency of research and development of new anti influenza drug. The CPSF30 binding pocket of effector domain in NS1 protein is very important in the replication of influanza A virus and is a new attractive anti flu drug target. But up to now there is no antiviral drug target this pocket. Here we employ molecular docking to screening of about 200,000 compounds. We find four novel compounds with high binding energy. Binding comformation analysis revealed that these small molecules can interact with the binding pocket by some strong hydrophobic interaction. This study find some novel small molecules can be used as lead compounds in the development of new antiinfluenza drug based on CPSF30 pocket.

Novel host markers in the 2009 pandemic H1N1 influenza a virus

The winter of 2009 witnessed the concurrent spread of 2009 pandemic H1N1 with 2009 seasonal H1N1. It is clinically important to develop knowledge of the key features of these two different viruses that make them unique. A robust pattern recognition technique, Random Forests, was employed to uncover essential amino acid markers to differentiate the two viruses. Some of these markers were also part of the previously discovered genomic signature that separate avian or swine from human viruses. Much research to date in search of host markers in 2009 pandemic H1N1 has been primarily limited in the context of traditional markers of avian-human or swine-human host shifts. However, many of the molecular markers for adaptation to human hosts or to the emergence of a pandemic virus do not exist in 2009 pandemic H1N1, implying that other previously unrecognized molecular determinants are accountable for its capability to infect humans. The current study aimed to explore novel host markers in the proteins of 2009 pandemic H1N1 that were not present in those classical markers, thus providing fresh and unique insight into the adaptive genetic modifications that could lead to the generation of this new virus. Random Forests were used to find 18 such markers in HA, 15 in NA, 9 in PB2, 11 in PB1, 13 in PA, 10 in NS1, 1 in NS2, 11 in NP, 3 in M1, and 1 in M2. The amino acids at many of these novel sites in 2009 pandemic H1N1 were distinct from those in avian, human, and swine viruses that were identical at these positions, reflecting the uniqueness of these novel sites.

Successful High-Dosage Dexamethasone Treatment of H1N1 Influenza A Pneumonia Complicated with Acute Necrotizing Encephalitis in an HIV-Infected Adult

Neurological manifestations in H1N1 influenza A infection are very rare, especially in adults, and its mechanism of action is still uncertain. Here, we reported the case of a 53-year-old woman with human immunodeficiency virus infection (HIV) who had H1N1 influenza A pneumonia complicated with very rare acute necrotizing encephalitis, although the HIV was under control. With prompt identification and administration of high dosage of dexamethasone, her mental status improved from stupor to clear, with minimal right hemiparesis. Further, brain magnetic resonance image revealed great resolution of mass effect. This dramatic improvement in response to the treatment may improve our understanding of the pathophysiology between H1N1 influenza A infection and acute necrotizing encephalitis.

Higher Viral Load and Prolonged Viral Shedding Period is Associated with Impaired Th17 Cell Response in Patients with H1N1 Influenza A

Objective To explore whether age,disease severity,cytokines and lymphocytes in H1N1 influenza A patients correlate with viral load and clearance.Methods Total of 70 mild and 16 severe patients infected with H1N1 influenza A virus were enrolled in this study.Results It was found that the patients under 14 years old and severe patients displayed significantly higher viral loads and prolonged viral shedding periods compared with the patients over 14 years old and mild patients,respectively(P < 0.05).Moreover,the patients under 14 years old and severe patients displayed significantly lower Th17 cell frequency than the patients over 14 years old and mild patients(P < 0.01).The viral shedding period inversely correlated with the frequency of IL-17+IFN-γ-CD4+ T cells.Additionally,the decreased concentration of serum TGF-β correlated with the decreased frequency of IL-17+IFN-γ-CD4+ T cells.Conclusions Both younger and severe patients are associated with higher viral loads and longer viral shedding periods,which may partially be attributed to the impaired Th17 cell response.

Reduning plus ribavirin display synergistic activity against severe pneumonia induced by H1N1 influenza A virus in mice

OBJECTIVE:To investigate synergistic effect of Reduning(RDN)injection plus ribavirin against severe pneumonia induced by H1 N1 influenza A virus in mice.METHODS:We established a mouse model of severe pneumonia induced by influenza A virus by infecting Balb/c mice with CA07 virus.We randomly assigned the infected mice into four groups,and treated them with normal saline(NS group),RDN(injection,86.6 mg/kg),ribavirin(injection,66.6 mg/kg)or double Ribavirin plus RDN group,the same dosage as used in the single treatments)for 5 d.Lung index and lung pathology were recorded or calculated in terms of the curative effective.Cytokines,NOD-like receptor family pyrin domain containing 3(NLRP3)inflammasome related protein including caspase-associated recruitment domain(CARD)domain Apoptosis-associated speck-like protein containing a caspase recruitment domain(ASC),caspase-1 and NOD-like receptor family,pyrin domain containing 3(NLRP3),and reactive oxygen species were simultaneously investigated.RESULTS:RDN plus ribavirin treatment,not RDN or ribavirin alone,provided a significant survival benefit to the influenza A virus-infected mice.The combination treatment protected the mice against severe influenza infection by attenuating the severe lung injury.The combined treatment also reduced the viral titers in mouse lungs and lung index,downregulated their immunocytokine levels,including IL-1βand IL-18,and down regulated the NLRP3,especially the transcription and translation of caspase-1.Meanwhile NS group had significantly higher reactive oxygen species(ROS)expression which could was dramatically reduced by the treatment of RDN plus ribavirin.CONCLUSION:Our study showed that RDN combined with ribavirin could protect the mice,and reduce the lung immunopathologic damage caused by severe influenza pneumonia.The mechanism could be that it reduced ROS produce and inhibited NLRP3 inflammasome activation so that mainly lower the downstream inflammatory cytokines IL-1βand IL-18.

HIF-1αpromotes virus replication and cytokine storm in H1N1 virus-induced severe pneumonia through cellular metabolic reprogramming

The mortality of patients with severe pneumonia caused by H1N1 infection is closely related to viral replication and cytokine storm.However,the specific mechanisms triggering virus replication and cytokine storm are still not fully elucidated.Here,we identified hypoxia inducible factor-1α(HIF-1α)as one of the major host molecules that facilitates H1N1 virus replication followed by cytokine storm in alveolar epithelial cells.Specifically,HIF-1αprotein expression is upregulated after H1N1 infection.Deficiency of HIF-1αattenuates pulmonary injury,viral replication and cytokine storm in vivo.In addition,viral replication and cytokine storm were inhibited after HIF-1αknockdown in vitro.Mechanistically,the invasion of H1N1 virus into alveolar epithelial cells leads to a shift in glucose metabolism to glycolysis,with rapid production of ATP and lactate.Inhibition of glycolysis significantly suppresses viral replication and inflammatory responses.Further analysis revealed that H1N1-induced HIF-1αcan promote the expression of hexokinase 2(HK2),the key enzyme of glycolysis,and then not only provide energy for the rapid replication of H1N1 virus but also produce lactate,which reduces the accumulation of the MAVS/RIG-I complex and inhibits IFN-α/βproduction.In conclusion,this study demonstrated that the upregulation of HIF-1αby H1N1 infection augments viral replication and cytokine storm by cellular metabolic reprogramming toward glycolysis mainly through upregulation of HK2,providing a theoretical basis for finding potential targets for the treatment of severe pneumonia caused by H1N1 infection.

Clinical characteristics of critical patients with pandemic influenza A(H1N1) virus infection in Chengdu,China

Objective： The critical illness of pandemic influenza A （H1N1） virus infection may be associated with relatively poor outcomes. The objective of this study is to describe clinical features and factors associated with the deaths of critical patients. Methods： Medical records of 26 critical patients with H1N1 infection admitted from Sept. 1 to Dec. 31, 2009, were retrospectively reviewed. Diagnosis was established by real-time reverse transcdptase- polymerase chain reaction （RT-PCR） assay. Results： The mean age of the patients was （40.4＋18.4） years and 73.1% of them were male. Clinical manifestations included fever, cough, and sputum production. The laboratory findings included leukocytosis, lymphopenia, C-reaction protein, and lactic dehydrogenase elevation. In this series, 17 subjects survived and 9 died. The parameters between the deaths and survivors were compared, which included acute physiology and chronic health evaluation II （APACHE II） scores （23.8＋10.1 vs. 14.3_＋6.6, P〈0.05）, sequential organ failure assessment （SOFA） scores （13.3_＋3.0 vs. 6.6_＋3.3, P〈0.05）, and multiple organ dysfunction syndrome （MODS） scores （7.4＋2.5 vs. 3.3＋1.7, P〈0.05）. The cases of deaths had higher incidences of cardiovascular failure （100% vs. 41.2%, P〈0.05）, renal failure （55.6% vs. 11.7%, P〈0.05）, encephalopathy （44.4% vs. 5.9%, P〈0.05）, hepatic failure （33.3% vs. 5.9%, P〈0.05）, and septic shock （33.3% vs. 17.6%, P〈0.05）. Conclusions： The critical patients with H1 N1 infection have high APACHE II, SOFA, and MODS scores, which may be associated with an increased risk of death and complex clinical courses.

Genetic characteristics of H1N1 influenza virus outbreak in China in early 2023

Dear Editor,Influenza A virus(IAV)exhibits rapid mutability and antigenic mutations.Since the 20th century,IAV has caused at least four pandemics(Yang et al.,2022).Presently,seasonal H_(3)N_(2)and H1N1 are the prevailing human-adaptive IAV subvariants responsible for human epidemics.The implementation of public health interventions since the commencement of the COVID-19 pandemic has effectively curtailed global influenza circulation(Olsen et al.,2021).Following the downregulation of the prevention and control strategies against COVID-19,global influenza activity is showing a recovery.

Severe Novel Influenza A(H1N1) in Shanghai:Clinical Features, Therapeutic Management and Risk Factors for Mortality

Objective To analyze the clinical features,therapeutic management and risk factors for mortality of patients with severe novel A(H1N1)influenza in Shanghai,China.Methods All patients were diagnosed by influenza A(H1N1)virus mRNA detection.Chest CT scan,routine blood,hepatic function,humoral and cellular immunity,sputum smears,and sputum cultures were performed.Logistic analysis was applied to identify risk factors for mortality.Results Total of 68 patients were enrolled in this study,the primary clinical symptoms including cough(66,97.1%),expectoration(41,60.3%),and polypnea(41,60.3%).Altogether,37(54.4%)and 11(16.2%)patients were infected with bacterial and fungal,respectively.CT scan demonstrated that 67(98.6%)patients had pneumonia.Oxygen therapy,oseltamivir,antibiotic and antifungal drugs were performed in 68(100%),66(97.1%),39(57.4%),and 11(16.2%)patients,respectively.Finally,4 of 68 patients died.Logistic analysis demonstrated that there was a significant correlation between the percentage of neutrophils and mortality before therapy and direct bilirubin content and mortality after therapy,respectively.Conclusions Patients with severe H1N1 influenza were susceptible to bacterial and/or fungal infection.The risk factors for mortality may be associated with pre-therapeutic neutrophil percentage and post-therapeutic direct bilirubin content.

Comorbid presentation of severe novel influenza A （H1N1） and Evans syndrome： a case report

One 22-month-old boy who was admitted for a fever lasting 6 days as well as a cough and wheezing lasting 2 days was reported. He was diagnosed with influenza A （H1N1, severe type）, severe pneumonia, acute respiratory distress syndrome （ARDS）, Evans syndrome and multiple organ failure. This is the first case of novel influenza A （HIN1） and Evans syndrome. The pathogenesis is still unknown.

Distinctive clinical and laboratory features of COVID-19 and H1N1 influenza infections among hospitalized pediatric patients

Background It had been documented in many studies that pediatric coronavirus disease 2019(COVID-19)is characterized by low infectivity rates,low mortalities,and benign disease course.On the other hand,influenza type A viruses are recognized to cause severe and fatal infections in children populations worldwide.This study is aimed to compare the clinical and laboratory characteristics of COVID-19 and H1N1 influenza infections.Methods A retrospective study comprising 107 children hospitalized at Abha Maternity and Children Hospital,Southern region of Saudi Arabia,with laboratory-confirmed COVID-19 and H1N1 influenza infections was carried out.A complete follow-up for all patients from the hospital admission until discharge or death was made.The clinical data and laboratory parameters for these patients were collected from the medical records of the hospital.Results Out of the total enrolled patients,73(68.2%)were diagnosed with COVID-19,and 34(31.8%)were diagnosed with H1N1 influenza.The median age is 12 months for COVID-19 patients and 36 months for influenza patients.A relatively higher number of patients with influenza had a fever and respiratory symptoms than COVID-19 patients.In contrast,gastrointestinal symptoms were observed in a higher number of COVID-19 patients than in influenza patients.A statistically significant increase in white cell counts is noted in COVID-19 but not in influenza patients(P<0.05).There are no obvious variations in the mean period of duration of hospitalization between COVID-19 and influenza patients.However,the total intensive care unit length of stay was longer for influenza compared to COVID-19 patients.Conclusions A considerable number of children infected with COVID-19 and H1N1 influenza were noted and reported in this study.There were no significant variations in the severity of the symptomatology and laboratory findings between the two groups of patients.Significant differences between these patients in some hospitalization factors and diagnosis upon admission also were not observed.However,more severe clinical manifestations and serious consequences were observed among pediatric patients hospitalized with influenza infections than among those with COVID-19.

Insights from investigating the interactions of natural product inhibitors with neuraminidase of the 2009 H1N1 influenza virus

Neuraminidase(NA) plays a biologically vital role in the replication of influenza virus, and NA inhibitors(NAIs) are most widely used in the clinical anti-flu therapy. NA of 2009 H1 N1 influenza virus(09 N1) possesses a different substrate-binding cavity compared with other NA subtypes, making 09 N1 a more appropriate starting point for the discovery of potent 09 N1 inhibitors. As natural products are of great structural diversity, research on the interaction between natural NAIs and 09 N1 can throw light on the design of new structural NAIs. In this study, we, for the first time, conducted molecular docking procedure with GOLD on 10 natural inhibitors to 09 N1, and acquired their binding modes with 09 N1. The docking results showed that the active site S1 was important in the binding of NAIs to 09 N1. Then five scaffolds were extracted from these NAIs with interactions to site S1, and these could be used in the structural modification of NAIs. Besides, we found that the addition of H-bonding interaction with the active site could improve the NA inhibitory activity of NAIs, and it might be the reason why the approved NAIs showed high efficiency. Two terminal hydrophobic sites(Terminal 1 and Terminal 2) with no interactions to the approved NAI zanamivir were found in the 09 N1 active cavity, and four NAIs were first found to bind with the terminals. Till now, there are few studies on the meaning of Terminal 2 in the binding of NAI to NA, which could be a new direction for the rational design of NAIs.