PANDEMICSCould Bird Flu in Mink Signal Threat of a Human Pandemic?

By Jeannette Cwienk

Published 7 February 2023

A bird flu outbreak on a Spanish mink farm has alarmed scientists. The virus may be spreading for the first time from mammal to mammal — and could become a danger for humans.

It started in October 2022, when several dead mink were discovered on a farm in Galicia in northwestern Spain. Veterinarians initially blamed the coronavirus. But tests revealed that the highly pathogenic avian flu virus H5N1 was the culprit.

To stop the spread of the dangerous pathogen, more than 50,000 mink on the farm were killed. 

While farm workers themselves were not infected, the case remains a cause of concern for scientists.

Mink Farm Outbreak ‘Incredibly Concerning’
The spread of the virus from birds to other species is nothing new. The pathogen that causes bird flu, or avian influenza, has been found in raccoons, foxes and seals, though these remain isolated cases.

While there have been some cases of H5N1 infecting humans, the World Health Organization has said there’s no evidence of human-to-human transmission so far. 

When the disease has spread to humans and other mammals, it has been via direct contact with excrement from infected birds or their carcasses, according to Timm Harder, an avian influenza expert at the Friedrich Loeffler Institute’s diagnostic virology department in Germany.

But the mink outbreak appears to be a rare case where mammals are transmitting the disease to each other rather than through direct contact with an infected bird. This is something “new,” said Harder.

Part of the problem is that mink are intensively farmed. They’re kept in high numbers in confined spaces, which means infection spreads rapidly in the highly susceptible mammals, said Harder.

Harder added that researchers have identified several pathogen mutations in the mink, one of which allows “the virus to better reproduce in mammals.”

Scientists are worried that the virus, which has led to the deaths of tens of millions of birds globally, could spread to more mink farms and become “more transmissible.”

This is incredibly concerning,” said Tom Peacock, a virologist at Imperial College London, in an interview with the scientific journal, Science. “This is a clear mechanism for a H5 pandemic to start.”

Could Avian Influenza Trigger a Human Pandemic?
Of the 868 known cases of H5N1 infection in humans worldwide between January 2003 and November 2022, 457 were fatal, according to the WHO.

However, because there has been no sustained human-to-human transmission, the risk of human infection from avian flu is low, said the WHO.

Some highly pathogenic avian influenza viruses have an increased potential to cause new zoonotic diseases — which are transmissible from animals to humans and vice versa.

While Timm Harder said there are “numerous hurdles for a more extensive adaptation to humans,” he added the mutations seen in the virus that infected mink must be further