Avian Influenza H5N1: Risks at the Human–Animal Interface

Abstract

Background: Great concern has arisen over the continued infection of humans with highly pathogenic avian influenza (HPAI) of the H5N1 subtype. Ongoing human exposure potentially increases the risk that a pandemic virus strain will emerge that is easily transmissible among humans. Although the pathogenicity of a pandemic strain cannot be predicted, the high mortality seen in documented H5N1 human infections thus far has raised the level of concern. Objectives: To define the three types of influenza that can affect humans, discuss potential exposure risks at the human–animal interface, and suggest ways to reduce exposure and help prevent development of a pandemic virus. Methods: This review is based on data and guidelines available from the World Health Organization, the scientific literature, and official governmental reports. Results: Epidemiological data on human exposure risk are generally incomplete. Transmission of HPAI to humans is thought to occur through contact with respiratory secretions, feces, contaminated feathers, organs, and blood from live or dead infected birds and possibly from contaminated surfaces. Consumption of properly cooked poultry and eggs is not thought to pose a risk. Use of antiviral containment and vaccination may protect against development of a pandemic. Conclusions: To most effectively decrease the risk of a pandemic, the public health and animal health sectors—those which are responsible for protecting and improving the health of humans and animals, respectively—must collaborate to decrease human exposure to HPAI virus, both by controlling virus circulation among poultry and by assessing the risks of human exposure to avian influenza virus at the human—animal interface from primary production through consumption of poultry and poultry products, and implementing risk-based mitigation measures.