Developing an Integrated Approach to Assess the Emergence Threat Associated with Influenza D Viruses’ Circulating in Europe

Recent studies have identified a new genus of the Orthomyxoviridae family, Influenza D virus (IDV). This virus was shown to infect farm animals including swine and cattle, and to efficiently replicate and transmit in ferrets (Hause et al., 2013; Liu et al., 2020), the animal model of choice for transmission of influenza A virus to humans. This partnering grant (Flu-D project) on IDV addressed the need for capacity building at EU level to improve the EU's scientific assessment capacity and international competitiveness. We have promoted cross-disciplinary cooperation between the partner institutes representing six Member States (BE, FR, IE, IT, LU, and SE). We have shown that the available antibody testing methods allow reliable influenza D diagnostics in partners’ laboratories but that molecular diagnostic systems required some primers/protocols adjustments. Serological results in European cattle suggest that influenza D virus is enzootic and antigenic maps generated with reference antisera showed 2 main antigenic clusters, matching the genetic clustering. Virus diversity is still unfolding with new virus introductions identified, as well as the discovery of new reassortants whose differential clinical impact or cross-protection levels are still poorly understood. A quantitative risk assessment model (QRAM) of IDV through introduction of cattle in a country or a herd was developed and refined including several mitigation measures (e.g. testing strategy, vaccination/biosecurity). Complementary, an innovative tool that estimated the biosecurity level of protection of a farm was developed and pre-tested. The present project led to ideas and data sharing, cross-consortium training, and to the sustainability of our influenza D network in Europe with perspectives on future collaborative projects.