Abstract
zoonotic influenza A virus subtype groups in 29 countries, Taiwan, and Hong Kong have caused human infections, with differing severity and frequency. The frequency of novel influenza virus detection is increasing, and human infections with influenza A(H5N1) and A(H7N9) viruses are now annual seasonal occurrences in Asia. The study of the epidemiology and virology of animal influenza viruses is key to understanding pandemic risk and informing preparedness. This supplement brings together select recent articles that look at the risk of emergence and transmission of and approaches to prevent novel influenza virus infections.
Influenza presents 2 major challenges to public health. The first comes from a small group of seasonal human influenza viruses that cause respiratory disease worldwide, especially notable as annual epidemics in temperate climes. Although seasonal influenza is generally of low severity, high annual attack rates globally result in substantial global respiratory and circulatory mortality, especially in high-risk groups such as the elderly. Seasonal influenza is vaccine preventable, although because the virus is constantly evolving, vaccine requires annual or semiannual updates to maintain its effectiveness. The second challenge is the threat posed by the emergence of a novel virus from a great reservoir of diverse influenza A viruses that exist among birds and other animals. These viruses can leap unpredictably across the species barrier to cause human illness and global pandemics with high case-fatality rates, such as occurred in 1918 and for which widespread vaccination may not be possible in time to prevent a significant number of illnesses and deaths. Key to this capability of influenza A viruses to change unpredictably is a segmented RNA genome that allows reassortment to create new viruses that are novel to the human immune system and can cause severe disease. The constant adaptation and exchange of genes between influenza viruses in different species, including at the animal-human interface, continue to pose a critical challenge to the prediction of and preparation for the emergence of pandemic viruses.
In this supplement, we bring together a selection of articles that reflect work to better understand influenza A viruses of zoonotic concern, their risk to public health and global health security, and effective measures to prevent their emergence as pandemic agents.