Local persistence and global dissemination play a significant role in the circulation of influenza B viruses in Leyte Island, Philippines

Analysis of influenza trend and impact of COVID-19 in Kezhou, Xinjiang for 8 consecutive years

To study the trend of influenza and the impact of coronavirus disease 2019 (COVID‐19) in Kezhou, Xinjiang from 2013 to 2020. The data of influenza in Kezhou, Xinjiang from January 1, 2013, to December 31, 2020, were collected by the China Influenza Surveillance Information System to study the trend of ILI proportion, the distribution of influenza‐like cases in different age groups, the positive cases and positive rate of influenza, and the trend of different influenza subtypes, and to analyze the impact of COVID‐19 epidemic on influenza. The proportion of ILI in the Xinjiang Kezhou area was mainly children under 15 years old, and children under 5 years old accounted for the largest proportion. The proportion of ILI, the number of influenza‐positive cases, and the influenza‐positive proportion were mainly in winter and spring, especially in December and January each year. At the same time, this study found that the overall trend of H3N2 influenza in this region was on the rise, and the outbreaks in 2018 and 2019 were dominated by novel H1N1 and H3N2, respectively. The trend of influenza in Kezhou, Xinjiang is on the rise, and the prevention and control measures of COVID‐19 have significantly reduced the data of influenza. It is necessary to strengthen the vaccination work and maintain the basic prevention and control measures of respiratory infectious diseases to prevent and control influenza more effectively.

[Comprehensive understanding of viral diseases by field, molecular, and theoretical studies]

Viral diseases are responsible for substantial morbidity and mortality and continue to be of great concern. To ensure better control of viral infections, I have been tackling the issue as a medical doctor, an academic researcher, and a public health officer. Especially, I have studied respiratory viruses, such as the influenza virus, from the perspectives of molecular virology, theoretical modeling, and field epidemiology. RNA biology and its involvement with viral life-cycle and pathogenicity are central topics of molecular study, while mathematical models of transmission dynamics and phylogenetics are major components of theoretical research. As a field epidemiologist, I work with public health authorities during viral disease outbreaks. I was deployed to West Africa for viral hemorrhagic fever outbreak responses as a WHO consultant, and I have served the Japanese Government as an advisor for COVID-19 countermeasures. I would like to integrate various approaches from clinical medicine to epidemiology, theoretical modeling, evolutionary biology, genetics, and molecular biology in my research. In that way, we could gain a more comprehensive understanding of viral diseases. I hope these findings will help ease the disease burden of viral infections around the world.

Characterization of Influenza A and B Viruses Circulating in Southern China During the 2017-2018 Season

The trivalent seasonal influenza vaccine was the only approved and available vaccine during the 2016–2018 influenza seasons. It did not include the B/Yamagata strain. In this study, we report an acute respiratory disease outbreak associated with influenza B/Yamagata infections in Guangzhou, Southern China (January through March, 2018). Among the 9914 patients, 2241 (22.6%) were positive for the influenza B virus, with only 312 (3.1%) positive for the influenza A virus. The influenza B/Yamagata lineage dominated during this period in Southern China. The highest incidence of influenza A virus infection occurred in the children aged 5–14 years. In contrast, populations across all age groups were susceptible to the influenza B virus. Phylogenetic, mutations, and 3D structure analyses of hemagglutinin (HA) genes were performed to assess the vaccine-virus relatedness. The recommended A/H1N1 vaccine strain (A/Michigan/45/2015) during both 2017–2018 and 2018–2019 was antigen-specific for these circulating isolates (clade 6B.1) in Spring 2018. An outbreak of influenza B/Yamagata (clade 3) infections in 2018 occurred during the absence of the corresponding vaccine during 2016–2018. The recommended influenza B/Yamagata vaccine strain (B/Phuket/3073/2013) for the following season (2018–2019) was antigen-specific. Although there were only a few influenza B/Victoria infections in Spring 2018, five amino acid mutations were identified in the HA antigenic sites of the 19 B/Victoria isolates (clade 1A), when compared with the 2016–2018 B/Victoria vaccine strain. The number was larger than expected and suggested that the influenza B HA gene may be more variable than previously thought. One of the mutations (K180N) was noted to likely alter the epitope and to potentially affect the viral antigenicity. Seven mutations were also identified in the HA antigenic sites of 2018–2020 B/Victoria vaccine strain, of which some or all may reduce immunogenicity and the protective efficacy of the vaccine, perhaps leading to more outbreaks in subsequent seasons. The combined epidemiological, phylogenetic, mutations, and 3D structural analyses of the HA genes of influenza strains reported here contribute to the understanding and evaluation of how HA mutations affect vaccine efficacy, as well as to providing important data for screening and selecting more specific, appropriate, and effective influenza vaccine candidate strains.

Influenza B associated paediatric acute respiratory infection hospitalization in central vietnam

Background

Influenza B is one of the major etiologies for acute respiratory infections (ARI) among children worldwide; however, its clinical‐epidemiological information is limited. We aimed to investigate the hospitalization incidence and clinical‐epidemiological characteristics of influenza B‐associated paediatric ARIs in central Vietnam.

Methods

We collected clinical‐epidemiological information and nasopharyngeal swabs from ARI children hospitalized at Khanh Hoa General Hospital, Nha Trang, Vietnam from February 2007 through June 2013. Nasopharyngeal samples were screened for 13 respiratory viruses using Multiplex‐PCRs. Influenza B‐confirmed cases were genotyped by Haemagglutinin gene sequencing. We analyzed the clinical‐epidemiological characteristics of influenza B Lineages (Victoria/Yamagata) and WHO Groups.

Results

In the pre‐A/H1N1pdm09 period, influenza B‐associated ARI hospitalization incidence among children under five was low, ranging between 14.7 and 80.7 per 100 000 population. The incidence increased to between 51.4 and 330 in the post‐A/H1N1pdm09. Influenza B ARI cases were slightly older with milder symptoms. Both Victoria and Yamagata lineages were detected before the A/H1N1pdm09 outbreak; however, Victoria lineage became predominant in 2010‐2013 (84% Victoria vs 16% Yamagata). Victoria and Yamagata lineages did not differ in demographic and clinical characteristics. In Victoria lineage, Group1 ARI cases were clinically more severe compared to Group5, presenting a greater proportion of wheeze, tachypnea, and lower respiratory tract infection.

Conclusions

The current results highlight the increased incidence of influenza B‐related ARI hospitalization among children in central Vietnam in the post‐A/H1N1pdm09 era. Furthermore, the difference in clinical severity between Victoria lineage Group1 and 5 implies the importance of influenza B genetic variation on clinical presentation.

Analyses of Evolutionary Characteristics of the Hemagglutinin-Esterase Gene of Influenza C Virus during a Period of 68 Years Reveals Evolutionary Patterns Different from Influenza A and B Viruses

Infections with the influenza C virus causing respiratory symptoms are common, particularly among children. Since isolation and detection of the virus are rarely performed, compared with influenza A and B viruses, the small number of available sequences of the virus makes it difficult to analyze its evolutionary dynamics. Recently, we reported the full genome sequence of 102 strains of the virus. Here, we exploited the data to elucidate the evolutionary characteristics and phylodynamics of the virus compared with influenza A and B viruses. Along with our data, we obtained public sequence data of the hemagglutinin-esterase gene of the virus; the dataset consists of 218 unique sequences of the virus collected from 14 countries between 1947 and 2014. Informatics analyses revealed that (1) multiple lineages have been circulating globally; (2) there have been weak and infrequent selective bottlenecks; (3) the evolutionary rate is low because of weak positive selection and a low capability to induce mutations; and (4) there is no significant positive selection although a few mutations affecting its antigenicity have been induced. The unique evolutionary dynamics of the influenza C virus must be shaped by multiple factors, including virological, immunological, and epidemiological characteristics.