A uncommon and complicated avian flu pressure in a toddler traveler reveals how globally circulating viruses are reshaping native outbreaks—and highlights crucial surveillance gaps in South Asia.
Influenza A (H5N1/hen flu) virus particles (spherical and rod-shaped; pink and yellow). Artistic composition and colorization/results by NIAID; transmission electron micrograph imagery is courtesy CDC. Scale has been modified/to not scale. Credit score: CDC and NIAID.
A workforce of Australian scientists has just lately recognized extremely pathogenic avian influenza A(H5N1) virus clade 2.3.2.1a in a toddler who traveled again to Australia from India.
They’ve characterised the virus and printed a report within the Heart for Illness Management and Prevention (CDC)’s journal Rising Infectious Ailments.
Background
Extremely pathogenic avian influenza (HPAI) A(H5N1) clade 2.3.4.4b has emerged from goose/Guangdong lineage HPAI H5N1 viruses after a long time of evolution. This viral clade circulates dominantly worldwide and causes an infection in wild and home birds and mammals.
Regardless of the worldwide predominance of clade 2.3.4.4b, a range of HPAI H5N1 clades at present flow into in poultry in Asia. Since 2005, greater than 900 zoonotic infections have been recorded. Contact with contaminated poultry is the first trigger of those infections. Nonetheless, human-to-human transmission has but to be detected.
Numerous HPAI H5N1 clades have been discovered to trigger human infections in Asia. Eleven human infections brought on by HPAI H5N1 clade 2.3.2.1c have been reported in Cambodia prior to now two years. In China, 91 human infections brought on by HPAI H5N6 and two infections brought on by clade 2.3.4.4b H5N1 have been recorded since 2014.
Extremely pathogenic avian influenza A(H5N1) virus clade 2.3.2.1a persistently circulates in South Asia, particularly in India and Bangladesh. Though this clade not often infects people, two circumstances have been detected in these areas to this point. Nonetheless, poultry-related outbreaks of H5N1 have been reported in Ranchi, India, in 2023 and 2024, roughly 400 km from Kolkata, the place the kid on this research visited.
On this research, scientists have characterised HPAI H5N1 clade 2.3.2.1a an infection in a toddler traveler returning to Australia from India.
Examine particulars
The research concerned a 2.5-year-old beforehand wholesome lady who returned to Australia after visiting Kolkata, India, in February 2024. The kid developed an sickness in Kolkata and was hospitalized after returning to Australia.
She was subsequently admitted to the intensive care unit (ICU) with respiratory failure requiring mechanical air flow. She was handled with a 5-day course of oseltamivir beginning on day 3 after admission. She absolutely recovered and was discharged after 2.5 weeks.
Respiratory samples collected from the affected person have been examined utilizing routine next-generation sequencing, which recognized the H5N1 virus, designated as A/Victoria/149/2024 (H5N1).
Characterization of the virus
The phylogenetic evaluation of the recognized virus revealed that it’s a reassortant virus consisting of 4 segments just like clade 2.3.2.1a viruses circulating in Bangladesh. The 4 segments have been hemagglutinin, neuraminidase, nucleoprotein, and nonstructural segments.
Additional evaluation revealed that the matrix section (regulation of viral replication) is just like HPAI H5N1 clade 2.3.4.4b viruses, which predominantly flow into worldwide and have been detected in birds in Asia.
The polymerase primary 2, polymerase primary 1, and polymerase acidic segments confirmed similarity with the latest clade 2.3.4.4b low pathogenicity avian influenza viruses detected in wild birds and poultry in Asia since 2020. This reassortment means that clade 2.3.4.4b viruses, which have disseminated globally by way of wild birds, are reworking the genetic construction of different H5N1 clades endemic in poultry.
Mammalian adaptation
The evaluation of viral segments for mammalian adaptation, virulence, and antiviral susceptibility indicated retention of preferential binding to avian α2–3 however to not the mammalian α2–6 sialic acid receptors.
The viral segments didn’t present any markers for mammalian adaptation, virulence, or pathogenicity. Nonetheless, the virus confirmed susceptibility to oseltamivir and baloxavir marboxil.
Examine significance
The research describes the identification and characterization of extremely pathogenic avian influenza A(H5N1) virus clade 2.3.2.1a in an Australian baby traveler getting back from India. The virus is a beforehand unreported reassortant consisting of clades 2.3.2.1a, 2.3.4.4b, and wild hen low-pathogenicity avian influenza gene segments.
These findings name for sturdy monitoring of significant influenza A circumstances in vacationers who’ve returned from areas with circulating avian influenza viruses. Subtyping these extreme and even deadly viruses, particularly H5N1 and H5N6 viruses at present circulating in South Asia, is important for lowering nonseasonal influenza infections and initiating antiviral therapies promptly.
The case research reported right here highlights the numerous lack of H5N1 surveillance knowledge in India, with solely two H5 sequences reported from the nation since 2020. In distinction, 314 sequences have been recorded in Bangladesh throughout the identical interval, additional underscoring the necessity for complete surveillance efforts.
The viral genome characterised on this research is just like that of a deadly case in New Delhi in 2021 and genetically just like the H5N1 viruses current in Bangladesh. Though the New Delhi case was brought on by contact with poultry, the present Australian case had no confirmed contact with poultry or uncooked poultry merchandise. This lack of confirmed publicity highlights the problem in figuring out the mode and route of an infection, significantly in areas with restricted knowledge on circulating viruses.
The advanced genetic recombination origins of the recognized virus reveal that clade 2.3.4.4b viruses proceed to play a significant position in shaping the evolution of different H5N1 clades, emphasizing the significance of world surveillance.
Total, the research highlights the necessity for elevated surveillance of persistent HPAI H5Nx infections in Asia.
