TAG: GS 3: SCIENCE AND TECHNOLOGY
THE CONTEXT: The spread of High Pathogenic Avian Influenza (HPAI) H5N1, commonly known as avian flu, has recently garnered significant attention due to its increasing transmission to various mammal species, including domestic cats.
EXPLANATION:
- This situation has raised concerns among scientists and health authorities about the potential risks of zoonotic spillover, where the virus could jump from animals to humans, potentially leading to a new pandemic.
Spread of Avian Flu to Mammals
- Since May 2022, avian flu has infected up to 23 mammal species, causing illness, severe disease, and even death in some cases.
- The US Department of Agriculture reported that 374 animals have contracted the virus, with the most affected species including 97 red foxes, 82 house mice, 43 skunks, and 36 domestic cats.
- Infections have also been documented in mountain lions (22 cases), harbor seals (21 cases), and various other species such as raccoons, deer mice, and bobcats.
Domestic Cats: A Growing Concern
- Among the various mammals affected, the spread of avian flu among domestic cats has become a major concern.
- Recent research indicates that the latest strain of H5N1 (clade 2.3.4.4b) poses increased risks to felines.
- The study, titled Avian Influenza Virus Infections in Felines: A Systematic Review of Two Decades of Literature, emphasizes the need for close monitoring of avian flu infections in felines, given the emerging threat of a human pandemic caused by the virus.
Potential for Zoonotic Spillover
- Domestic cats, which often serve as human companions, have the potential to act as pathways for the transmission of avian influenza viruses to humans.
- Felines are known to feed on dead wild birds, which may carry the virus, thereby becoming hosts for the virus’s adaptation to mammals.
- The study also highlighted instances of feline-to-feline transmission, suggesting that the virus could spread within feline populations, further increasing the risk of zoonotic spillover.
Rise in Feline Infections
- Over the past two decades, the study found that 2023 saw the highest number of infections in domestic cats, coinciding with the spread of the latest H5N1 clade among mammals.
- The researchers identified approximately 486 cases of avian flu virus infections in felines, with 249 resulting in death.
- The current strain of H5N1 has shown a 67% fatality rate in infected cats, underscoring the severity of the situation.
Geographic Distribution of Infections
- The study documented avian flu infections in 12 feline species across seven geographical regions and 17 countries.
- Asia, particularly Southeast Asia, reported the highest rate of infection at 54%, followed by Europe at 24% and North America at 12%.
- Infections in felines have been reported not only in the US but also in Finland, Italy, France, Peru, Poland, and South Korea.
- These infections have affected domestic cats as well as wild felines like bobcats, lynx, lions, and caracals.
Transmission Pathways and Human Risk
- The majority of feline avian flu cases have resulted from bird-to-feline transmission, where infected birds were fed to the cats.
- However, three cases involved feline-to-feline transmission, and two cases involved infection from cattle that were fed raw milk and colostrum.
- Despite these alarming developments, the US Centers for Disease Control and Prevention (CDC) has classified the risk to humans as low, with no direct human infections reported from cats to date.
- Since March 2024, there have been 13 human cases of avian flu reported in the US, linked to 189 dairy herds across 13 states.
- However, these cases have not been directly connected to domestic cats or other mammal species, and the overall risk of human infection remains low according to current data.
Avian Flu or H5N1
- Avian flu refers to an infectious viral illness that mainly infects and spreads among poultry and some wild birds.
- There are different strains of bird flu virus, which have been circulating for a very long time among at least 100 bird species, including wild waterfowl, such as ducks and geese, without much harming them.
- From time to time, a form of the flu virus jumps from wild birds to poultry farms, and replicates in cramped warehouses of farmed birds.
- It then quickly evolves into a highly pathogenic flu virus that causes a larger wave of illness and death than usual among birds.
- The currently circulating type of H5N1 is one such highly pathogenic flu virus.
- It has “descended from a virus that caused an outbreak on a goose farm in Guangdong, China, in 1996.
- That virus — one of a type of virus known as H5N1 — was highly pathogenic and killed more than 40 per cent of the farm birds it infected.
- The new version of H5N1 first emerged in Europe in 2020 and then rapidly reached Europe, Africa, and Asia.
- By late 2021, it had spread to North America and in the fall of 2022, it appeared in South America.
- In February 2024, the virus stormed through mainland Antarctica.
