New Avian H5N1 Flu Strain Spreads Faster Than Ever: Study

Dec 05, 2024
News

New Avian H5N1 Flu Strain Spreads Faster Than Ever: Study (Image Credits: iStock)

A recently identified strain of avian flu shows low infectious rates but an increased ability to transmit through the air, according to a study published in Nature Microbiology. This development raises concerns about its potential impact on public health and livestock industries worldwide.
The virus strain, isolated from a polecat, mink, and an infected dairy worker in Texas, carries mutations that enhance its ability to spread via air. Researchers from Erasmus University Medical Center in the Netherlands identified two mutations: PB2-E627K, found in the Texas strain, and PB2-T271A, observed in polecat and mink strains. Both mutations were shown to enable transmission between ferrets, an animal model commonly used to study influenza due to its similarities to human infection.
The study highlights the urgency of containing outbreaks, particularly among cattle, to minimize the risk of transmission to farm workers and other mammals. Additionally, the possibility of milk contamination underscores the broader implications for public health.
Ferrets: Model for Influenza Research
To evaluate the virus’s transmission capabilities, scientists conducted experiments on ferrets, which serve as an ideal model for studying influenza. Ferrets mimic human flu infection patterns and transmission routes, making them invaluable for assessing public health risks.
In the study, ferrets were exposed to aerosol samples containing airborne virus particles. The experiment tested six different viruses, including the 2009 H1N1 seasonal flu, the 2005 H5N1 wild-type virus from Indonesia, and modified strains. Among the samples, viruses from 2024—part of clade 2.3.4.4b—showed notable transmissibility. This clade has been rapidly spreading among poultry, wild birds, and various mammals, causing a global epizootic.
Spread and Impact in the US
In March 2024, the virus was detected in dairy cows in the United States, subsequently spreading across 695 dairy herds in 15 states. Among humans, 55 cases have been reported, mostly linked to exposure to infected poultry or cattle.
Testing on ferrets revealed that one in four of the animals became infected when exposed to strains from the polecat and dairy worker. However, the 2005 H5N1 strain from Indonesia did not transmit via air, emphasizing the evolving nature of the newer strains.
“Our results indicate that recent A(H5N1) viruses exhibit a low but increased level of infectious virus shedding into the air compared with older A(H5N1) viruses,” the researchers stated.
Concerns About Mammalian Adaptation
The study raises alarms about the virus’s potential adaptation to mammals, including humans. The researchers observed that airborne-transmissible viruses replicate more efficiently in the upper respiratory tract, releasing higher viral RNA levels into the air compared to non-transmissible variants.
“These findings align with previous studies showing that airborne-transmissible viruses exhibit faster replication and release in the air, increasing the risk of transmission,” the study noted.
Proactive Measures: Vaccine Development
In response to the potential threat, the United Kingdom has contracted the production of over five million doses of the human H5 influenza vaccine. The vaccine will be manufactured by CSL Seqirus UK Limited, a leading vaccine producer.
“It is important for us to be prepared against a range of different influenza viruses that may pose human health risks,” said Meera Chand, Emerging Infection Lead at the UK Health Security Agency, in a press statement.
As avian flu strains continue to evolve, the study underscores the importance of rigorous surveillance, timely containment measures, and proactive public health preparedness. Enhanced research and vaccine development efforts will be critical in mitigating the risks associated with this emerging threat.
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