H5N1

1. Context 

2. Avian Influenza

• Avian Influenza, also known as Avian or Bird Flu, is a form of influenza caused by a virus found in birds.
• Avian Flu is similar to variants found in animals and humans – caused strains of influenza that have adapted to specific hosts.

3. Avian Influenza Type A viruses

• Type A viruses are classified based on two proteins on their surfaces – Hemagglutinin (HA) and Neuraminidase (NA). There are about 18 HA subtypes and 11 NA subtypes.
• Several combinations of these two proteins are possible e.g., H5N1, H7N2, H9N6, H17N10, H18N11, etc.
• All known subtypes of influenza A viruses can infect birds, except subtypes H17N10 and H18N11, which have only been found in bats.

Image Source: The Hindu

4. Effect on Birds

• Although avian influenza has different subtypes, H5N1 is a highly pathogenic subtype that causes mortality in birds.
• Since 2022, the virus has infected over 100 million birds across the globe, resulting in the deaths of over 50 million and the culling of millions of poultry.
• Unlike previous outbreaks of highly pathogenic subtypes of avian influenza, H5N1 is heavily impacting wild bird species, including many which were on the verge of extinction. 
• While it is difficult to ascertain how many wild birds have been affected by the virus, a significant impact has been seen in eagles, pelicans, geese, waterfowl, gulls, falcons, and shorebirds, in addition to the highest possible impact on poultry seen till date, at least in the U.S.
• The impact of H5N1 on wild bird populations has varied depending on several factors, such as the level of exposure, geographical locations, and migratory patterns of the affected species. 
  
• High mortality in wild birds due to the virus could lead to significant ecological consequences, including the vulnerability of predators and alterations in species composition in affected ecosystems, and therefore a possible impact on biodiversity not just limited to avian species. 
• It has raised concerns regarding the spread of the virus among critically endangered avian populations.  

5. Spreading to animals

• The highly contagious H5N1 virus can also occasionally spill over from birds to animals through direct or indirect contact with infected birds or their droppings. 
  
• Worryingly, there have been several reports on the spillover of H5N1 to mammals during the current outbreak from different countries, infecting species such as sea lions, minks, foxes, wild bears, and skunks, apart from domestic animals such as dogs and cats.
• In 2023 alone, H5N1 caused the deaths of over 3,000 sea lions in Peru. In a recent yet ­to­ be peer ­reviewed study, scientists found that the virus could efficiently spread between ferrets in the laboratory.
  
• The only known cases of the virus spreading between mammals were reported in minks that were raised in close confinement on a farm in Spain.
• The transmission of H5N1 from birds to mammals is rare, but when it does occur, it can be a cause for concern, as the virus could accumulate mutations and acquire the ability to potentially initiate human outbreaks.
• H5N1 has a high mortality rate of over 60% in humans and is primarily transmitted to humans through close contact with infected birds or animals, either through handling infected poultry or exposure to contaminated environments.

6. Enhanced Measures

• As the current H5N1 outbreak continues unabated with devastating impact on the avian population globally, and with significant ecological and economic consequences, the time has never been better to initiate efforts for preparedness towards building better, more efficient vaccines for avians and humans.
• Genomic surveillance should be done to map the continued evolution of the virus.
• Moreover, enhanced biosecurity measures are required to protect both animal and public health.

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