Avian Influenza: Proactive Surveillance Under the “One Health” Framework

The recent avian influenza outbreak that ravaged India in late 2020 and early 2021 was marked by high infection and mortality rates among wild birds. Every affected region of the country moved quickly to step up surveillance and measures aimed at controlling the spread of the disease within its borders. This episode highlights the need to proactively monitor outbreaks in the wild, protect the natural environment to curb the spread of disease, and deepen our understanding of the interface between wildlife and domestic animals.   Avian influenza is a highly contagious viral disease that affects both domestic and wild birds. The disease is present worldwide, but different viral strains—some more lethal than others—are distributed across various regions of the globe. According to the World Organisation for Animal Health (WOAH), wild waterfowl, such as geese and ducks, are the natural reservoirs of influenza A viruses, from which regular re-emergences occur. India has become a global hotspot for the circulation of the highly pathogenic H5N1 influenza virus. The country lies at the heart of the Central Asian flyway, which spans 30 countries and supports 279 populations of 182 species of waterbirds. It provides both a vital wintering refuge for many species of migratory waterfowl and year-round habitat for several resident bird species, including domesticated birds. The most recent avian influenza outbreak affected 14 Indian states in late 2020 and early 2021. It was characterized by a high infection rate and significant mortality among wild animals. The highly pathogenic H5N1 and H5N8 viral strains were detected in poultry and wild birds. As of February 12, 2021, a total of 449,271 poultry had been culled to control the spread of the disease, in accordance with the National Action Plan for the Prevention, Control, and Containment of avian influenza. Could this have been prevented? To be better prepared and respond more effectively in the event of the emergence of new pathogens or viral strains, researchers propose implementing year-round passive and active surveillance in risk areas. This would require rapid tests to confirm the cause of death in wild birds. Viruses are, in fact, highly sensitive to temperature. Their RNA degrades very rapidly when exposed to heat. A simplified system is therefore needed to analyze samples in real time as cases are reported, in order to immediately determine the cause and the viral strain. This outbreak particularly highlights the importance of proactive surveillance to understand the prevalence of avian influenza viruses and prevent them through early warnings—but not only that. There is an urgent need to better understand the virus’s interactions with its potential hosts and the environment. Surveillance of wildlife and its interactions with livestock populations and the environment would help fill the gaps in our knowledge on this subject, which are hindering prevention policies. Integrating surveillance into the “One Health” framework—which would encompass the entire virus transmission network—would lead to a better understanding of the behavior of avian influenza viruses as a whole, thereby enabling more accurate predictions of virus emergence. Indeed, while it is known that a wide variety of species and cold water temperatures enhance viral survival in certain regions of the world, the role of poultry in viral circulation in India implies that this pathogen is active there year-round, even outside the migratory season. The higher the poultry density, the greater the risk of an epidemic. This is evidence that the interaction between poultry and wild birds fuels H5N1 outbreaks. Water also plays a role. Since the virus is shed through the intestinal tract, bodies of water can serve as vectors of transmission. In fact, the risk of an outbreak is highest on poultry farms that have access to bodies of water inhabited by wild species, regardless of the density of the birds. Proximity to lakes, rivers, and coastal wetlands is particularly conducive to the emergence of avian influenza on poultry farms. These factors are further exacerbated by the fact that unprotected wetlands are often under constant pressure from urbanization and pollution. Avian influenza and other zoonotic diseases are present in the environment, and as human activities encroach on the natural habitats and biotopes used by wild species, the risk of transmission increases. With habitat loss and the increase in poultry populations, the buffer zone between wild birds and domestic birds is shrinking, leading to more interactions and transmissions. It is therefore essential to involve communities in the management of unprotected wetlands if we are to hope to limit future avian influenza outbreaks. Everything is interconnected and interrelated. With these factors in mind, a geographical study of certain regions would make it possible, in particular, to identify risk areas for an outbreak in order to break the cycle of viral transmission—for example, by preventing the mixed use of surface water by domestic poultry and wild species. In this context, the “One Health” framework of viral interconnections and interactions provides key insights for predicting, minimizing, and controlling outbreaks, benefiting wildlife, agriculture, the environment, and human health alike.