2023-08-16 14:09:00
Bird flu outbreaks are fairly common and pose a significant threat to wild birds, poultry and – if the bird flu virus acquires enough mutations – possibly even humans. Currently, the highly pathogenic H1N1 subtype is spreading at an unprecedented rate in North America and Europe.
To better understand the dynamics of avian flu epidemics, a team of scientists led by ETH Zürich recently investigated the epidemic caused by another subtype of avian flu (H7N9) in China from 2013 to 2017, which not only decimated a large number of poultry, but also killed 616 people who had been in close contact with infected poultry.
Experts analyzed published genetic sequences of H7N9 viruses isolated from infected poultry and humans in metropolitan Shanghai and Guangdong to build phylogenetic trees that could reveal how the disease spread in Chinese poultry markets, which play a key role in transmission between animals, as well as from animals to humans.
Analyzes provided evidence that the H7N9 virus was likely circulating in poultry for several months before it was first detected in poultry markets and in humans, suggesting that between 2013 and 2016 – when the virus has caused relatively few symptoms in poultry – it has actually affected more markets. than previously thought. As the virus mutated and started causing more severe symptoms in poultry from 2016, affected animals were easier to identify.
“Our results underscore the importance of not waiting until cases of bird flu are discovered, because then the virus has probably already been circulating for some time,” said the study’s lead author, Tanja Stadler, professor of biostatistics. and Computational Evolution at ETH Zürich. “Instead, it would be wise to continuously monitor the health of animals in their barns and in live poultry markets. »
Although some scientists have speculated that the virus was repeatedly introduced between regions by carrying infected birds, the phylogenetic trees that the researchers reconstructed show no such pattern, suggesting that it rather quietly circulated through various poultry markets in urban areas before being first detected.
Despite the fact that the H7N9 outbreak was limited to China due to improved hygiene measures in poultry markets, as well as a mass poultry vaccination campaign that started in 2017 – initiatives capable of significantly mitigating the outbreak in animals and dramatically reducing rates of transmission to humans – isolated outbreaks are still occurring (with the last recorded human death in 2019), highlighting the insidious nature of bird flu epidemics.
Additionally, as virus genomes constantly mutate, the risk of H7N9 and other influenza strains becoming a threat to birds and mammals (including humans) remains. These results underscore the need for more effective and coordinated efforts to detect influenza infections early, in order to avoid massive outbreaks that could potentially lead to a new pandemic.
The study is published in the journal Proceedings of the National Academy of Sciences.
—
Par Andrei Ionescu, Terre.com Personal editor
1692199096
#learn #previous #bird #flu #outbreaks