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Changes in the H5N1 virus are 'concerning', according to the ECDC, and may suggest its potential to jump to humans is increasing. Mutations spotted in the H5N1 bird flu virus are “concerning” and may suggest the potential for avian influenza to jump to humans is increasing, according to the European Centre for Disease Control. In a situation report published this week, the agency said that although the threat in Europe remains low for the general public, and low to moderate for those in frequent contact with birds, the risk assessments contain “high uncertainty” That’s because the increasing transmission of H5N1, including its introduction to the Americas and the spread in animals, has offered unprecedented opportunities for the virus to shift and reassort – a process where different strains of the same pathogen combine into something new. “The expansion of mammal species identified infected with A(H5N1) viruses, as well as the detection of viruses carrying markers for mammalian adaptation in other genes such as the PB2 that correlated with increased replication and virulence in mammals, is of concern,” the ECDC said this week. “Although the virus retained a preferential binding for avian-like receptors, several mutations associated to increased zoonotic potential were detected. The PB2 gene was recently identified in mink in Spain. H5N1 jumped from wild birds to thousands of farmed animals – within weeks, more than four per cent had died from haemorrhagic pneumonia. In total, 50,000 mink were culled. “In most of the mammalian cases where the virus has been sequenced, we have seen a specific mutation in the PB2 gene, which allows the virus to replicate at a different body condition,” Dr
Michelle Wille, an expert in avian viruses at the University of Sydney, previously told the Telegraph. “The mutation is cropping up more because there are more mammalian cases, which is likely [because of] the staggering number of avian cases.” She added that in experiments in ferrets from a decade ago, scientists identified a handful of mutations that would be needed to allow for efficient mammal-to-mammal transmission. Unlike PB2, these have not yet been spotted in nature – but the more transmission that occurs, the greater the risk that this could occur. Last month a woman in China was hospitalised with H5N1, while a young girl died earlier this month and her father was quarantined in Cambodia after contracting the virus. Sequencing of the Cambodia cases found that the virus did have the mutations expected to allow it to infect humans, but that there were no signs that the pathogen has changed to better spread between people. “The small adaptations we observe have been detected in spillover events into humans in the past, and have not resulted in sustained human-to-human transmission,” said Dr Erik Karlsson, director of the National Influenza Center of Cambodia and acting head of virology at the Institut Pasteur du Cambodge, which sequenced the virus. In the latest ECDC assessment, the agency said any reports of transmission events to and potentially between animals should be closely followed – especially in pigs, which are known to harbour both animal and human diseases. Just yesterday, Canada announced that eight skunks found dead in late February in Richmond and Vancouver were infected with avian influenza. They likely contracted the diseases after scavenging infected wild birds, according to officials. The ECDC also warned that there are no signs of the outbreak dwindling, and that the circulation of H5N1 may instead increase in the coming months, as “breeding bird colonies move inland with possible overlap with poultry production areas”.
ECDC report (March 13, 2023):
https://www.ecdc.europa.eu/sites/default/files/documents/avian-influenza-overview-march-2023.pdf
