With reports of avian flu sweeping through minks in Spain, foxes in the UK, and now other mammals across the world, concern is growing about the threat both to human and animal health from H5N1. Although the position from WHO is that the risk to humans is “low”, experts are unsure about the implications that the increasing infections in mammals will have.  

Human risk 

The messaging at the moment is clear: the risk to humans is low. However, as Gavi notes, the “more often bird flu infects mammals, the more chance it has to evolve” to infect mammalian hosts better. This ability to mutate was of concern when experts noticed genetic mutations in samples from the infected minks in Spain that have also been seen in other infected mammals.  

“This could be the lightning fuse that gives it the ability to spread between people.”  

On the other hand, Gavi reminds us to consider the many changes that would need to happen before we see “real transmission capability”.  

Past pandemics 

Another point that Gavi raises is the possibility that the pandemic influenza in 1918 could have been a bird flu, mutated to affect the upper airways for greater transmissibility. However, things were different then, with no vaccines or antivirals. Are we in a better position to face an influenza pandemic? 


The call to vaccinate birds in the UK resounded against the official position that ineffective vaccination could in fact undermine containment efforts. For people, we have a couple of options that “do not produce really good, strong immune responses”, WHO’s Professor Ian Barr told Gavi. Furthermore, potential to scale up is limited by the development process.  

WHO’s message in February 2023 was of caution, but emphasised the organisation’s intent to “engage with manufacturers to make sure that if needed, supplies of vaccines and antivirals would be available for global use”.  

Agricultural concerns 

From a different perspective, experts are also worried about the consequences of these outbreaks on the agricultural industry. Professor Tim Uyeki of the CDC told Stat News that it presents a “major problem”. Professor Marion Koopmans of Erasmus Medical Centre warns that we are “playing with fire”. Each new outbreak increases the chances of mutation, and adds fuel to the fire of fear.  

The question remains, will we handle this emerging threat with the surveillance and sensitivity that WHO is encouraging, or will we allow things to escalate further? For more on how we plan to address this growing threat, come to the World Vaccine Congress in Washington