United States: Health experts and authorities have raised concerns because there is a high chance that bird flu, which was first reported in a poultry farm in 1996, will transform into a major threat and can trigger a flu pandemic.
The concerns have been raised after the flu has shown mutations and newer sub-types and clades have been seen. It is to be noted that since 2021, the virus has targeted as many as 485 species, including 25 from bird groups and 48 from mammal species. By mid-2024, as many as 142 outbreaks had been reported among animals across the world, including penguins and polar bears, according to Down to Earth.
It is to be noted that majorly the outbreaks have been seen in five geographical regions and were linked to various strains, such as HxNx (1), H5Nx (48), H5N1 (85), H5N5 (2), H7N5 (1) and H7N8 (5). The experts have outlined that these strains pose a growing threat of a potential pandemic.
HPAI now targets different mammals!
Earlier, HPAI was only associated with dangers to poultry, but now the infection has evolved to infect wild birds as well as other mammals, raising the concerns of the World Health Organisation (WHO) that could be responsible for the next global pandemic.
According to the data shared by the US Centers for Disease Control and Prevention (CDC), for the first time, the H5N1 strain was reported in a domestic waterfowl in southern China, and during that time, around six (6) humans lost their lives because of the same in China as well as Hong Kong. The incident was reported in 1997, as per the reports by Down to Earth.
Since that time, the virus has caused infection to 860 people, and the mortality rate has also exceeded 50 percent. The United Nations has mentioned that since its initial detection, the virus can be recognized as a public health concern.
Following this time, the virus was again reported in China and other parts of Asia in the year 2003 – when it caused widespread outbreaks. The infection continued to spread, and by 2005, the infection was detected among different continents, including Africa, the Middle East, and Europe.
With the passing of time, the hemagglutinin (HA) gene of the virus diversified into various genetic groups (clades), and between the years 2014 and 2016, the multiple genetic lineages, which are commonly referred to as genotypes, also started to detect. Along with this, the gene swapping resulted in the emergence of the new subtypes, which were named H5N6 and H5N8.
The HA gene once diverged into clade 2.3.4.4, propagated across the continents of Asia, Africa, Europe, the Middle East, and North America. Within this vast geographic spread, H5 viruses amalgamated with various neuraminidase (NA) genes, detected in wild avians and domesticated fowls alike.
Emerging between 2018 and 2020, a new variant, clade 2.3.4.4b of H5N1, proliferated globally by 2021-2023, as per Down to Earth.
Research highlights that millions of birds have succumbed, either directly due to infection or culled as a containment measure, on a global scale.
In 2022, this clade inflicted a grievous toll on marine life, claiming the lives of thousands of marine mammals in South America. A pre-print study titled Massive Outbreak of Influenza A H5N1 in Elephant Seals at Península Valdés, Argentina: Increased Evidence for Mammal-to-Mammal Transmission chronicled an unprecedented mortality event involving approximately 17,000 southern elephant seals in October 2023.
This year alone, H5N1 has infiltrated 191 bovine herds across 13 states in the US, infecting over 100 million animals across 48 states. The virus has now been identified in the most remote areas of the globe, including Antarctica, with concerns that it may soon reach the Pacific Islands and New Zealand — territories hitherto untouched.
The Food and Agriculture Organization of the United Nations has indicated that the clade 2.3.4.4b A (H5N1) viruses, though resulting in a limited number of human cases, have triggered significant outbreaks among mammalian species, including aquatic mammals, according to Down to Earth.
Among humans, officials have documented 15 new cases of the virus contracted from poultry and dairy cattle. Between 2003 and 2023, 878 individuals tested positive for the H5N1 virus, with 458 fatalities, reflecting a mortality rate of 52 percent.
The CDC has voiced concern over mutations observed in diverse mammal species, particularly in the ongoing panzootic, deeming them a substantial threat.
A study published in The Lancet in May 2024 cautioned that the pandemic risk posed by this virus remains elevated. For avian influenza viruses to become pandemics, they must achieve human-to-human transmission and replicate efficiently. The study noted that “this typically necessitates reassortment with human influenza viruses, or the virus could undergo adaptation — a process that might be protracted but could be hastened by frequent infection of mammals and humans,” according to Down to Earth.
In an April 2024 email interview, Professor Suresh Kuchipudi, chair of the Department of infectious diseases and microbiology at the Center for Vaccine Research, University of Pittsburgh School of Public Health, US, remarked, “While we cannot precisely predict the virulence of the virus should it gain the capacity for human transmission, it is prudent to assume — based on current data — that it is likely to cause more severe disease in humans than COVID-19, and we must prepare for this potential global health emergency.”