Epidemiological and Virological Characterization of Influenza B Virus Infections

While influenza A viruses comprise a heterogeneous group of clinically relevant influenza viruses, influenza B viruses form a more homogeneous cluster, divided mainly into two lineages: Victoria and Yamagata. This divergence has complicated seasonal influenza vaccine design, which traditionally contained two seasonal influenza A virus strains and one influenza B virus strain. We examined the distribution of the two influenza B virus lineages in Israel, between 2011-2014, in hospitalized and in non-hospitalized (community) influenza B virus-infected patients. We showed that influenza B virus infections can lead to hospitalization and demonstrated that during some winter seasons, both influenza B virus lineages circulated simultaneously in Israel. We further show that the influenza B virus Yamagata lineage was dominant, circulating in the county in the last few years of the study period, consistent with the anti-Yamagata influenza B virus antibodies detected in the serum samples of affected individuals residing in Israel in the year 2014. Interestingly, we found that elderly people were particularly vulnerable to Yamagata lineage influenza B virus infections

Forty Five Percent of the Israeli Population were Infected with the Influenza B Victoria virus During the Winter season 2015-16

While infection with influenza A viruses has been extensively investigated, infections with influenza B viruses which are commonly categorized into the highly homologous Victoria and Yamagata lineages, are less studied, despite their considerable virulence. Here we used RT-PCR assays, hemagglutination inhibition assays and antibody titers to determine the levels of influenza B infection. We report of high influenza B Victoria virus prevalence in the 2015-16 winter season in Israel, affecting approximately half of the Israeli population. We further show that the Victoria B virus infected individuals of all ages and that it was present in the country throughout the entire winter season. The vaccine however included the inappropriate Yamagata virus. We propose that a quadrivalent vaccine, that includes both Yamagata and Victoria lineages, should be considered for future influenza vaccination

Epidemiological and Virological Characterization of Influenza B Virus Infections.

While influenza A viruses comprise a heterogeneous group of clinically relevant influenza viruses, influenza B viruses form a more homogeneous cluster, divided mainly into two lineages: Victoria and Yamagata. This divergence has complicated seasonal influenza vaccine design, which traditionally contained two seasonal influenza A virus strains and one influenza B virus strain. We examined the distribution of the two influenza B virus lineages in Israel, between 2011-2014, in hospitalized and in non-hospitalized (community) influenza B virus-infected patients. We showed that influenza B virus infections can lead to hospitalization and demonstrated that during some winter seasons, both influenza B virus lineages circulated simultaneously in Israel. We further show that the influenza B virus Yamagata lineage was dominant, circulating in the county in the last few years of the study period, consistent with the anti-Yamagata influenza B virus antibodies detected in the serum samples of affected individuals residing in Israel in the year 2014. Interestingly, we found that elderly people were particularly vulnerable to Yamagata lineage influenza B virus infections

Phylogenetic tree.

<p>Bayesian maximum-clade-credibility time-scaled phylogenetic tree (BEAST) generated using 74 partially sequenced influenza B HA gene (476 bp), obtained from patient samples collected between 2012 and 2014 in Israel.</p

Temporal of influenza B infection.

<p>The percentages of hospitalized (A) and community (B) patients, during the winter seasons of 2011–2014. *p<0.05.</p

Infections with influenza viruses in Israel between 2011–2014.

<p>The percent of hospitalized (A) and community (B) patients infected with influenza A(H3N2), B and A(H1N1)pdm viruses between 2011–2014. *p<0.05.</p

Viruses included in the vaccine.

<p>Viruses included in the vaccine.</p

Gender distribution in hospitalized patients.

<p>The gender distribution of hospitalized Victoria-infected (A) and Yamagata-infected (B) patients between 2011–2014.</p

Age distribution of the influenza B-infected patients.

<p>The yearly age distribution of hospitalized (A) and community (B) patients positive for infection of influenza B viruses: Victoria and Yamagata between 2011–2014. Summary of the ages over the years in shown in (C-D).</p