Researchers have revealed that a 13-year-old girl from British Columbia, Canada, who was hospitalised in November 2024 after contracting bird flu, was infected with clade 2.3.4.4b, genotype D1.1 of the Highly Pathogenic Avian Influenza (HPAI) A or H5N1 virus. This strain is currently spreading widely among wild bird populations globally.
The same genotype was also detected in a worker in Louisiana, the United States, who was hospitalised in December 2024 after exposure to infected birds in a backyard poultry flock.
In findings published in The New England Journal of Medicine on December 31, 2024, scientists emphasised the urgent need for vigilant surveillance of emerging mutations and an assessment of the potential for human-to-human transmission.
“The mutations evident in the Canadian case highlight the urgent need for vigilant surveillance of emerging mutations and assessment of the threat of human-to-human transmission,” the researchers stated.
The samples from the teenaged patient, collected a week after the onset of symptoms, revealed three mutations potentially linked to increased virulence and human adaptation: E627K in the polymerase basic 2 gene and E186D and Q222H in the H5 haemagglutinin gene. However, it remains unclear whether these mutations were present in the infecting virus or emerged during the course of the illness.
The patient, who had a history of mild asthma and elevated body mass index, experienced severe symptoms, including cough, vomiting, diarrhoea and fever. Despite her relatively high viral load, treatment alleviated these symptoms and she was discharged on November 28, 2024 with improved respiratory status.
In an accompanying editorial, scientists stressed the importance of a coordinated approach to address the threat posed by HPAI. “These reports show several critical features of the threat of HPAI to human health and how we might respond,” they wrote, calling for collaboration among human and veterinary medicine, public health leadership, healthcare providers and occupational authorities, particularly in agriculture.
“The One Health paradigm is foundational to this outbreak, yet to date, genomic sequencing data that have been collected from animals frequently lack critical metadata,” the researchers underlined.
Further findings from a study of 46 infected individuals in the US revealed that 45 cases were linked to animal exposure, including poultry and cattle, with one case having an undetermined source. The median age of those infected was 34 years and all experienced mild symptoms, such as conjunctivitis, fever and respiratory issues.
None of the patients were hospitalised and no fatalities were reported.
“Among the 45 case patients with animal exposures, the median age was 34 years and all had mild A (H5N1) illness; none were hospitalised and none died. A total of 42 patients (93 per cent) had conjunctivitis, 22 (49 per cent) had fever and 16 (36 per cent) had respiratory symptoms; 15 (33 per cent) had conjunctivitis only,” the study detailed.