Bird Flu 2016 Variant Came Close to Human Receptor Binding, Highlighting Pandemic Risks

Recent research has revealed that a bird flu virus sampled in 2016 and no longer circulating was merely a single mutation away from acquiring the ability to bind to human cell receptors. This discovery underscores the potential threat posed by certain avian influenza strains, which could adapt to infect humans more readily and possibly lead to a pandemic.

The studies conducted by Utrecht University researchers, including Robert de Vries and Geert-Jan Boons, examined how bird flu viruses interact with cell receptors in different species. Viruses need to attach to specific receptors to infect host cells, and these receptors vary among animals. While bird flu viruses, particularly the H5N1 subtype, can cause severe disease in birds and occasionally infect mammals like minks, seals, and cattle, they have not yet been able to sustain human-to-human transmission.

In their analysis of two bird flu variants from 2016, researchers found that one required several mutations to gain the ability to bind human receptors, whereas the other needed only a single mutation. Remarkably, this single mutation could have enabled the virus to infect human cells, highlighting how close some strains are to crossing species barriers.

Further investigations focused on the current circulating bird flu in American cattle. Despite initial concerns, recent findings published in Nature show that this strain binds to bird, but not human, receptors. This specificity is linked to receptor differences; cow receptors are more similar to bird receptors than to human ones. Therefore, the current circulating virus remains unlikely to infect humans, but the proximity of these viruses to the ability to do so remains concerning.

While this situation does not constitute an immediate threat, experts emphasize the importance of vigilant monitoring. De Vries stresses that the virus's potential to evolve necessitates close observation and thorough testing of new variants. The differing approaches to bird flu containment between the U.S. and Europe highlight the importance of strict biosecurity measures, such as culling infected farms, to prevent the virus from further evolution and spillover into humans.

The ongoing presence of bird flu in animals and its occasional human infections underscore the risks associated with intensive livestock farming and close animal-human interactions. As outbreaks continue globally, experts warn that failure to manage these viruses properly could have serious public health consequences in the future.