ABSTRACT
BACKGROUND Influenza viral load (VL) can be a decisive factor in determining the antiviral efficacy in viral clearance. OBJECTIVE This study aimed to evaluate the rate of infection and the role of influenza VL on the clinical spectrum of illnesses among different patient groups attended at a tertiary hospital in Brazil. METHODS Samples were collected from patients presenting acute respiratory infection from 2009 to 2013. Overall, 2262 samples were analysed and distributed into three groups: (i) asymptomatic (AS); (ii) symptomatic outpatients (OP); and (iii) hospitalised patients (HP). VL (expressed in Log10 RNA copies/mL) was calculated through a quantitative real-time one-step reverse transcription-polymerase chain reaction (RT-PCR) assay aimed at the M gene, with human RNAseP target as internal control and normalising gene of threshold cycle values. FINDINGS A total of 162 (7.16%) H1N1pdm09 positive samples were analysed. Patients aged from 0.08 to 77 years old [median ± standard deviation (SD): 12.5 ± 20.54]. Children with 5 to 11 years old presented the highest detection (p < 0.0001). AS patients had the lowest VL, with a significant difference when compared with symptomatic patients (p = 0.0003). A higher VL was observed within two days of disease onset. Ten patients (HP group) received antiviral treatment and were followed up and presented a mean initial VL of 6.64 ± 1.82. A complete viral clearance for 50% of these patients was reached after 12 days of treatment. MAIN CONCLUSIONS It is important to evaluate AS patients as potential spreaders, as viral shedding was still present, even at lower VL. Our results suggest that patients with underlying diseases and severe clinical symptoms may be considered for prolonged viral treatment.
Subject(s)
Humans , Male , Female , Infant, Newborn , Infant , Child, Preschool , Child , Adolescent , Adult , Aged , Young Adult , Respiratory Tract Infections/virology , Influenza, Human/virology , Influenza A Virus, H1N1 Subtype/genetics , RNA, Viral/genetics , Acute Disease , Viral Load , Influenza A Virus, H1N1 Subtype/classification , Influenza A Virus, H1N1 Subtype/pathogenicity , Real-Time Polymerase Chain Reaction , Middle AgedABSTRACT
Objective@#To understand the epidemiological characteristics of influenza A(H1N1)pdm09 virus in Sichuan population during the monitoring period of 2018-2019, and to clarify the antigenic variation, the gene characteristics and the matching of current epidemic strains, vaccine strains, representative strains at home and abroad.@*Methods@#A total of 118 strains of influenza A(H1N1)pdm09 virus isolated in Sichuan region influenza network laboratory from April 2018 to March 2019 were selected. The hemagglutination inhibition (HI) assay was conducted for antigen analysis. The HA and NA genes of 16 strains with low-response strains were sequenced. Phylogenetic analysis and amino acid locus variation analysis were applied using BioEdit and MEGA5.0 software.@*Results@#The result of the antigen analysis demonstrated that more than 95% of the A(H1N1) pdm09 influenza viruses detected were similar to the WHO recommended vaccine strain A/Michigan/45/2015. The analysis of HA gene characteristics showed that some low-response strains had amino acid site variation in the Sa, Sb and Cb regions of the HA protein. A total of 15 low-response strains belonged to the 6B.1 branch. And their evolutionary relationship were close to the representative strains A/beijin-xicheng/SWL1633/2018 and A/brisbane/02/2018, which were popular at home and abroad. Compared with A/sichuan/1/2009, there are mutations involving 6, 14 and 1 amino acid sites in the antigen-determining regions (Sa, Sb, Ca and Cb), non-determined regions and receptor binding site(RBS) respectively. No amino acid site mutations related to resistance to NA gene were found.@*Conclusions@#In 2018-2019, the epidemic A(H1N1) pdm09 influenza virus in Sichuan is consistent with the global epidemic characteristics, which also matched with vaccine strains recommended by WHO in the northern hemisphere. Compared with A/sichuan/1/2009 which was the first isolated in China in 2009, there were amino acid sites mutations in antigen-determining region and receptor binding site of the HA protein, and the transmembrane region of the NA protein, drug and antibody binding sites.
ABSTRACT
Objective@#To evaluate the effect of vaccine and provide scientific evidence for prevention and control of influenza virus, this study aims to analyze the characteristics of genomic variation of influenza A (H1N1) pdm09 viruses in Inner Mongolia.@*Methods@#The 16 viral strains were selected randomly according to the influenza A (H1N1) pdm09 viruses isolated from network laboratories in Inner Mongolia, 2013-2017. The hemagglutinin(HA) and neuraminidase(NA) genomic sequences were obtained by using RT-PCR and sequencing, and genomic characteristics were analyzed via bioinformatics.@*Results@#Compared to the A/California/07/2009 vaccine strain, the relatively obvious variation of antigen of influenza A (H1N1) pdm09 viruses in Inner Mongolia since 2014, and the vaccine provided a poor protection to influenza A (H1N1) pdm09 virus infection, while the A/Michigan/45/2015 vaccine strain recommended by WHO recently has a satisfactory protective effects. Several viral isolates from Inner Mongolia increased the binding force of virus in human upper respiratory tract because of D222N and D222G substitution within HA. E119K and H275Y substitution within NA gene of viral strains, suggesting that the viruses were resistant to NA inhibitors.@*Conclusions@#The influenza A (H1N1) pdm09 viruses had gradual variations as time went on, and the WHO recommended vaccine was relatively lagging. Virulent strains and drug-resistant strains appeared in the population, and the genetic characteristics of influenza virus surveillance should be strengthened to find the new mutants of virus in time, which provide evidence for the prevention and control of influenza.
ABSTRACT
To study the biological characteristics and mutations of influenza A(H1N1)pdm09 virus isolated from one case of pneumonia of unknown etiology (PUE),which would provide references for clinical treatment and disease control,the throat swab specimen from the PUE case was isolated in the Madin-Darby Canine Kidney (MDCK) cells,and then the antigenicity,pathogenicity and drug resistance of influenza A (H1N1) pdm09 virus were analyzed after sequencing.As a result,one influenza virus strain was isolated from the specimen and named as A/FujianGulou/SWL64/2016(H1N1).The similarities of nucleotide sequences and amino acids sequences compared with the vaccine strain A/California/07/2009 (H1N1) were 96.9％-98.9％ and 96.7％-99.5％,respectively.Eighteen amino acids had mutated in the HA and 4 mutations,K163Q,S185T,S203T and D222N,were involved in 3 different epitopes,which indicated that the antigenic drift had occurred in the influenza virus.The D222N mutation associated with receptor binding site made the virus infect lower respiratory tract more easily.The virus was still amantadine-resistance and oseltamivir-sensitive.In conclusion,the influenza A (H1N1) pdm09 virus in this study have occurred antigenic drift and has the molecular characterization of causing severe pneumonia,so further surveillance should be performed to prevent and control the influenza epidemic.
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Objective@#To understand the viral etiology of a clustered case of human infection outbreak in the middle school of Huai’an city.@*Methods@#Nasopharyngeal swab samples from patients were collected and rapidly detected by Real-time RT-PCR and the target virus isolated in cells. Furthermore, HA1 segments of target virus were amplified by RT-PCR and sequenced. The genetic and phylogenetic analysis based on HA1 genes was computed.@*Results@#Influenza A(H1N1)pdm09 viral nucleic acid in 11 nasopharyngeal swab samples from patients in the outbreak were positive. Compared to the vaccine strains A/California/07/2009, the Huai’an isolates, nucleotide identity was 97.7%-98.1%, and amino acid identity was 96.6%-97.4%. Phylogenetic analysis of HA1 segment sequences indicated that the Huai’an strains from the outbreak were related closely to the viruses isolated in the year of 2014. Sequence analysis indicated that the Huai’an isolates had no amino acid substitution in the receptor binding sites and glycosylation sites, while in the Ca1 of antigenic determinant of HA1 the Huai’an isolates had an amino acid substitution of S for T at 220.@*Conclusions@#The pathogen of the clustered case of human infection was Influenza A(H1N1)pdm09 virus. Though the Huai’an isolates had one animo acid substitution in the Ca1 of antigenic determinant, the antigenicity characteristic remained unchanged.