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 Orthomyxoviridaefamily, 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 requiredsome 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 unfoldingwithnew 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 wasdeveloped 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.