Over the past year, at least 46 countries have recorded outbreaks of the bird flu strain H5N8 among both poultry and wild waterfowl. As a result, millions of birds across Europe, Asia and Africa have been culled.
In December 2020, the first H5N8 infections in humans were recorded, with seven Russian poultry workers testing positive for the virus. Although the people did not display any symptoms, the chickens did not fare so well. More than 100,000 from the 900,000-strong flock died.
Bird flu comes in a variety of different subtypes, with H5 and H7 particularly concerning due to their potential to affect humans and other animals (there was an outbreak of H5N1 bird flu in captive tigers in 2004).
Although rare in humans, bird flu can be deadly. Since 2003, there have been 862 cases of H5N1 bird flu worldwide. More than half of the people who caught H5N1 died.
Fortunately, human-to-human transmission has occurred in only a handful of cases. Most infections arise from contact with sick birds. But the ease with which influenza viruses can mutate means that the threat of a bird-flu pandemic looms large.
In June, China reported the first confirmed human infection of H10N3 bird flu, a rare strain. Scientists are calling for increased surveillance of poultry farms and wild birds—to find strains with pandemic potential, before they find us.