A One Health Imperative for Global Health Governance

Avian influenza or bird flu (caused by the H5N1 virus) is a contagious viral disease affecting domestic and wild birds and, less frequently, mammals. Authorities confirmed an outbreak in Kerala in late December, impacting poultry farms. While birds are the natural reservoir for this category of influenza viruses, transmission to humans occurs through contact with infected birds or contaminated settings such as poultry farms and markets where birds are sold. Human-to-human transmission of H5N1 has not yet been reported. However, over the past several years, scientists have warned of its potential to cross the species barrier — from infecting birds to humans — triggering a global health crisis. This threat underscores the urgency of understanding and addressing diseases that emerge at the human-animal interface and the significance of a ‘One Health’ approach to global health governance.

The World Health Organization (WHO) approximates that the flu infects 1 billion individuals every year, leaving 3-5 million with severe illness, of which hundreds of thousands are fatal.

Flu Through the Ages

The flu has been a public health threat for centuries, with the first documented influenza pandemic having occurred as early as 1510. The World Health Organization (WHO) approximates that the flu infects 1 billion individuals every year, leaving 3-5 million with severe illness, of which hundreds of thousands are fatal. Belonging to the family of viruses known as orthomyxoviruses, several different subtypes of influenza viruses exist, with influenza A and B posing significant threats to humans. Notably, influenza A has caused 4 pandemics since the beginning of the 20^th century, influenza B has never caused a pandemic, influenza C causes mild diseases, and influenza D does not infect humans. The 1918 Spanish Flu was caused by an influenza A strain, H1N1, which affected a third of the world’s population at the time and caused 50 million deaths globally. Each year, different influenza A and B strains emerge, causing seasonal flu. For instance, in the United States, the Centers for Disease Control and Prevention (CDC) reported that the 2024-2025 flu was caused primarily by H1N1 and H3N2 strains.

Avian Influenza

Meanwhile, bird flu infections — another influenza A subtype (H5N1) — have been rising globally over the past several years, following the first reported case in China in 1996. According to the World Health Organization (WHO), between 2003 and 2024, 900 human H5N1 cases were reported, with a fatality rate of 48 percent. A genetically related H1N1 virus, commonly known as swine flu, caused a pandemic in 2009, with global deaths estimated between 151,700 and 575,400. The current H5N1 outbreak began in 2021 in North America and has affected over 180 million birds. In addition, 1,000 dairy herds have been affected since H5N1 was first detected in dairy cows in March 2024. Seventy cases of H5N1 have been reported in humans in the US, including one death.

Closer to home, H5N1 was detected last month in Kerala after a large number of ducks and chickens died unexpectedly. Rapid Response Teams (RRTs) immediately implemented biosecurity protocols comprising culling operations and the destruction of eggs and poultry feed.

Closer to home, H5N1 was detected last month in Kerala after a large number of ducks and chickens died unexpectedly. Rapid Response Teams (RRTs) immediately implemented biosecurity protocols comprising culling operations and the destruction of eggs and poultry feed. Surveillance and containment measures have been heightened across the state to control the spread of the disease. In January 2025, three tigers and one leopard died in Maharashtra after being infected by H5N1. This marked the first case of the disease causing death amongst wildlife held in captivity in India.

Impact of Avian Influenza

The World Health Organization (WHO) places the public health risk posed by H5N1 as low for the general population and low to moderate for individuals exposed through occupational factors. There are no commercially available H5N1 vaccines for humans, as infections remain comparatively rare, indicating that population-level vaccination is not considered necessary. Moreover, seasonal flu vaccines are not designed to protect against avian influenza.

Avian influenza not only affects animal health and causes animal mortality, but it also impacts food security, global food supply chains, and disturbs biodiversity. For instance, the current outbreak in the US triggered egg shortages and price escalation, and caused a decline in overall milk yield, as H5N1 reduces milk production in dairy cattle. Collectively, this demonstrates how avian influenza outbreaks have the potential to create food security and economic challenges that extend beyond the human and animal health sector, impacting trade and global supply chains.

Collectively, this demonstrates how avian influenza outbreaks have the potential to create food security and economic challenges that extend beyond the human and animal health sector, impacting trade and global supply chains.

Viral Genome Reassortment

Presently, the main concern highlighted by scientists is the potential for an avian influenza strain to undergo significant genetic changes that would allow it to cross the species barrier and directly infect humans. Influenza viruses are RNA viruses that tend to accumulate mutations or minor genetic changes on a regular basis. These changes may alter their infectivity or pathogenicity and form the basis for why new flu vaccines are needed almost every year. Larger genetic changes may enable them to jump from infecting one species to another. This occurs in influenza viruses through genetic reassortment or the swapping of genetic material between flu strains and can occur when a human or animal cell is infected with two kinds of virus simultaneously. Figure 1 illustrates how a potential genetic reassortment could occur if a human cell were to be infected by an avian flu virus and a seasonal flu virus simultaneously, resulting in a novel strain with unknown pathogenicity and no existing vaccine, capable of infecting humans.

Figure 1. Diagrammatic representation of how a flu virus reassortment would occur

Source: Scientific American

While this is very rare, reassortment was responsible for all but one of the human flu pandemics, including the 2009 swine flu pandemic, where genetic reassortment of human, swine, and bird influenza viruses occurred. Reassortment between avian influenza strains is relatively common and has been occurring with increasing frequency since 2020. Scientists are concerned that since numerous H5N1 strains are circulating in poultry, wild birds, and dairy cows, concomitant with seasonal flu strains, it may only be a matter of time before a new strain emerges. A recent modelling study by Indian researchers demonstrated that in the case of H5N1, sustained human-to-human transmission will likely occur after 2-10 individuals are infected. The study highlights how narrow the window is between a zoonotic spillover event and sustained transmission amongst humans. While reassortments are infrequent, monitoring of potential changes requires continual surveillance across human, animal, and environmental systems.

While this is very rare, reassortment was responsible for all but one of the human flu pandemics, including the 2009 swine flu pandemic, where genetic reassortment of human, swine, and bird influenza viruses occurred.

Pandemic Agreement

Globally, there have been no cases of H5N1 transmission between humans. Nevertheless, viral spread across species and geographies, exacerbated by climate change and the COVID-19 pandemic underscore the need for a ‘One Health’ approach to controlling disease. In May 2025, the World Health Assembly adopted the landmark Pandemic Agreement, which includes One Health, acknowledging that previous frameworks struggled to address zoonotic diseases effectively. A part of the agreement – the Pathogen Access and Benefit Sharing (PABS) mechanism – that deals with the sharing of pathogen information with pandemic potential and the development of medical countermeasures to tackle disease is still being negotiated. The Intergovernmental Working Group (IGWG) that works on the draft text will reconvene this month to deliberate over the operationalisation aspects of PABS, including the effective implementation of a One Health approach. This includes global coordination and implementation at national levels to ensure that surveillance, reporting, and data-sharing occur across public health, veterinary, agricultural, food, and environmental sectors and engage with local communities and high-risk populations like poultry farmers.

Conclusion

The next global health crisis could very well be of zoonotic origin. The widespread nature of the ongoing H5N1 outbreak impacts not only animal and human health but also endangers species diversity and the supply of animal-sourced foods. The occurrence of infection (and fatalities) in mammals underscores the virus’s ability to infect multiple species, including humans. Effectively operationalising a One Health approach to emerging global health challenges within a global governance framework is now of utmost importance.

Lakshmy Ramakrishnan is an Associate Fellow with the Centre for New Economic Diplomacy at the Observer Research Foundation.

The views expressed above belong to the author(s). ORF research and analyses now available on Telegram! Click here to access our curated content — blogs, longforms and interviews.