Genetic changes power H5N1 virus spread, severity in animals
Why in news:
- A study published recently has found that the H5N1 virus (clade 184.108.40.206b), which spread among wild birds across 30 countries or territories across continents by February 2022 collected different combinations of genes through reassortment with viruses circulating in wild birds in North America.
- The reassortant A(H5N1) viruses are genotypically and phenotypically diverse, with many causing severe disease with dramatic neurologic involvement in mammals.
- The viruses have distinct in vitro characteristics including increased virus replication rates and ability to cause severe disease outcomes with dramatic neurologic involvement in mammalian animal models.
- The virus has a proclivity to target the central nervous system.
- Influenza A virus subtype H5N1 (A/H5N1)is a subtype of the influenza A virus which can cause illness in humans and many other species.
- A bird-adapted strain of H5N1, called HPAI A(H5N1)for highly pathogenic avian influenza virus of type A of subtype H5N1, is the highly pathogenic causative agent of H5N1 flu, commonly known as avian influenza (“bird flu”).
- It is enzootic (maintained in the population) in many bird populations, especially in Southeast Asia.
- One strain of HPAI A(H5N1) is spreading globally. after first appearing in Asia.
- It is epizootic (an epidemic in nonhumans) and panzootic (affecting animals of many species, especially over a wide area), killing tens of millions of birds and spurring the culling of hundreds of millions of others to stem its spread.
- HPAI A(H5N1) is considered an avian disease, although there is some evidence of limited human-to-human transmission of the virus.
- A risk factor for contracting the virus is handling of infected poultry, but transmission of the virus from infected birds to humans has been characterized as inefficient.
Spread to animals:
- The highly contagious H5N1 virus can also occasionally spillover from birds to animals through direct or indirect contact with infected birds or their droppings.
- There have been several reports on 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.
- 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.
- It is primarily transmitted to humans through close contact with infected birds or animals, either through handling infected poultry or exposure to contaminated environments.
- In the recent months, a few sporadic cases of human H5N1 infections have also been reported from Ecuador, Cambodia, and more recently in Chile.
- However, since the virus does not yet transmit efficiently among humans, the World Health Organization (WHO) has assessed the risk of H5N1 to humans to be low.