Bird flu viruses gaining function through natural mixing, warn scientists

The bird flu virus’ resurgence began with an 11-year-old. In February 2023, the schoolgirl was admitted to a hospital in Phnom Penh with severe pneumonia – within a day, she was dead. Tests soon revealed that she had contracted avian influenza: Cambodia hadn’t reported a human case of bird flu since 2014, but the hiatus was over. Since then, 39 more people have been infected and 15 have died in the Southeast Asian country – a case fatality rate of roughly 40 per cent. Researchers have been scratching their heads as to why, after nine years, this particular stain of H5N1 suddenly started jumping from birds to people again. The strain or clade called 2.3.2.1 had been circulating for almost a decade without spilling into humans. What changed? Now, a paper in Emerging Infectious Diseases offers clues. Scientists say the apparent rise in human cases has coincided with the virus gaining new genetic material and, potentially, new powers of infection, from a second flu virus via a process known as “reassortment”.