Avian Influenza A(H5)

Due to the ongoing threat of Highly Pathogenic Avian Influenza A(H5N1) to animal and human health, the Center for Outbreak Response Innovation (CORI) conducted a scenario-based risk assessment to consider human health risks both now and in potential future scenarios. Risk assessments aim to enable structured consideration of complex scenarios, likelihoods, and consequences to determine the negative health impacts that may occur and inform decisions around future policy and operational action. Risk assessments allow policymakers to understand how the implementation of protective measures and future planning for worst-case scenarios can improve health outcomes. These assessments offer value by providing a systematic way to estimate risk with incomplete or imperfect information; this is critical because decisions must be made even in the absence of plentiful data. Therefore, the risk assessment will be updated as additional data become available.

The purpose of this document is to consider possible future developments regarding HPAI A(H5N1) transmission and describe corresponding risks to human populations in the US should a given scenario occur. In each scenario, we consider the risk to four distinct populations: people in regular contact with affected animal populations (e.g., farm workers, veterinarians, backyard flock owners), close contacts of those individuals, healthcare workers, and the general public. In determining these risks, we consider several factors, including transmission pathways, animal-to-human transmission dynamics, morbidity and mortality rates, the outbreak’s current status, and potential events that could exacerbate the situation. Additionally, the assessment considers the effectiveness of preventive measures, ongoing response operations, and political factors that may influence the outbreak’s progression.