Differences in Patient Age Distribution between Influenza A Subtypes

Since the spring of 1977, two subtypes of influenza A virus (H3N2 and H1N1) have been seasonally infecting the human population. In this work we study the distribution of patient ages within the populations that exhibit the symptomatic disease caused by each of the different subtypes of influenza virus. When the publicly available extensive information is pooled across multiple geographical locations and seasons, striking differences emerge between these subtypes. We report that the symptomatic flu due to H3N2 is distributed across all age groups, whereas H1N1 causes symptomatic disease mainly in a younger population. These distinct characteristic spectra of age groups, possibly carried over from previous pandemics, are consistent with previous findings on the evolutionary dynamics of each subtype. Moreover, they are relevant to age-related risk assessments, modeling of epidemiological networks for specific age groups, and age-specific vaccine design. Recently, a novel H1N1 virus has spread around the world. Preliminary reports suggest that this new strain causes symptomatic disease in the younger population in a similar fashion to the seasonal H1N1 strains

Direct-acting antiviral treatment outcomes in people infected with endemic compared to epidemic hepatitis C virus subtypes in England.

Background: Current evidence suggests reduced efficacy of direct-acting antiviral (DAA) treatment among people with endemic Hepatitis C virus (HCV) subtypes rare to high-income countries. We aimed to determine real-world DAA treatment outcomes of people with endemic HCV subtypes in England. Methods: Data were collected through a national treatment program. People who had their virus subtyped between 2019-2023, were resident in England and had an outcome recorded for their first DAA treatment episode, were included. Subtypes were divided into epidemic and endemic in England; endemic subtypes were confirmed with whole genome sequencing and resistance associated substitutions (RAS) were determined. Logistic regression was used to determine associations between treatment outcome and exposure variables. Results: In people with an outcome recorded, 93 with an endemic and 8671 with an epidemic HCV subtype were identified, of whom 49.5% (46/93) and 91.8% (7953/8668) achieved a sustained virological response at 12 weeks post end of DAA treatment (SVR12), respectively. In the multivariable model, people with an endemic subtype had 93% (aOR 0.07 95%CI 0.04-0.12, P=<0.001) reduced odds of achieving SVR12. Treatment with sofosbuvir/velpatasvir or glecaprevir/pibrentasvir was successful for genotypes 1, 2, 4 and 5 (SVR12 100%, n=13) but not 3 (27.3%, n=22) endemic subtypes. Sofosbuvir/velpatasvir/voxilaprevir was successful for GT3 endemic subtypes at retreatment (SVR12 11/12, 91.7%). Treatment failures for genotypes 1, 3 and 4 were likely mediated by naturally occurring baseline NS5A RAS (median n=2). Discussion: This study provides further evidence that endemic HCV subtypes lead to sub-optimal DAA efficacy, which may impact global HCV elimination