by Avian influenza, commonly known as bird flu, is caused by infection with avian influenza (AI) virus strains that occur naturally among wild aquatic birds worldwide and can infect domestic poultry and other bird and animal species. The AI viruses do not normally infect humans. However, there is always a risk that an AI virus might mutate or reassort into a strain that is easily transmissible among humans and cause a pandemic.
Types of Bird Flu Viruses
There are different subtypes of avian influenza viruses based on two types of proteins on their surface: hemagglutinin (H) and neuraminidase (N). The H and N subtypes currently known to circulate in avian species include H5, H7, and H9.
– H5N1: The highly pathogenic H5N1 virus has spread globally and caused massive poultry outbreaks and some severe human infections Bird Flu. It was first detected in a goose in Guangdong, China in 1996 and spread to over 60 countries by 2006, causing huge economic losses.
– H7N9: A low pathogenic H7N9 virus emerged in China in 2013 and has since caused multiple waves of human infection. Most cases have had contact with live poultry. H7N9 poses an ongoing global public health threat due to recurring epidemics among humans.
– H9N2: H9N2 is a low pathogenic avian influenza virus that has been circulating in poultry in Asia and the Middle East since the late 1990s. It can infect and cause illness in humans on rare occasions.
Possible Pandemic Scenarios
While most AI viruses do not infect humans, they are constantly evolving which poses a risk of developing the ability to spread easily between people. There are primarily two ways this could potentially occur:
- Antigenic shift: This happens when an AI virus undergoing reassortment acquires gene segments from a human influenza virus. If the resulting hybrid virus retains the ability to infect humans while becoming easily transmissible, it could cause a pandemic.
- Gradual mutation: An AI virus may acquire mutations favoring its proliferation in humans while retaining stability in avian species through incremental changes over several months or years. This slow adaptation process could generate a pandemic strain without needing prior exposure to human viruses.
Global Surveillance and Response Efforts
In response to the pandemic potential of highly pathogenic AI, intensive surveillance programs have been established globally to monitor the viruses in domestic and wild bird populations. The WHO has developed a pandemic preparedness framework to help countries and the international community respond quickly and effectively through containment, communication, and collaboration.
When outbreaks occur, control strategies focus on stamping out the disease through culling of infected flocks, movement restrictions, quarantines, disinfection, and vaccination in some regions. Early detection through monitoring, prompt reporting, and rapid response are critical to controlling the spread and preventing pandemics. Public education regarding risks and appropriate handling of poultry also plays an important role.
Regional Bird Flu Impacts and Risks
Asia: Countries like China, Vietnam, Indonesia, Bangladesh, India face recurring H5N1, H7N9 outbreaks often linked to live bird markets. Millions of birds are culled during epidemics causing huge economic losses. Millions living in close proximity to poultry are at risk.
Africa: H5N1 spread to over 20 countries from 2005-2010. Poultry sectors collapsed as birds were culled. Surveillance remains limited in many resource-poor regions increasing likelihood of undetected spread or outbreaks.
Europe: Migratory wild birds play a role in AI virus introduction and spread. Countries conduct intensive surveillance and rapid response to contain outbreaks in commercial and backyard flocks. Risk of transmission to highly populated areas remains.
North America: Commercial poultry are highly vulnerable. Past H5N1, H7N3 outbreaks were contained through coordinated control programs avoiding wider spread. Risk exists from movements of wild birds and poultry/poultry products.
Human Cases and Pandemic Potential
Since 2003, 860 laboratory confirmed human cases of H5N1 infection have been reported to WHO, of which 455 died. However, sustained human-to-human transmission has not occurred so far. Sporadic cases of H7N9, H9N2 in humans have also been reported from different parts of the world.
While none of the currently circulating avian viruses have gained the ability to spread easily between humans, the continuing circulation in poultry and the risk of antigenic shift/mutation mean they pose an ongoing pandemic threat. Changes as small as 1-2 amino acids in the H or N proteins can enable airborne transmission in humans. An uncontrolled epidemic could have catastrophic consequences worldwide unless rapidly contained. Preparedness to respond to such a crisis is crucial.
*Note:
1. Source: Coherent Market Insights, Public sources, Desk research
2. We have leveraged AI tools to mine information and compile it
