When it comes to coronavirus we are getting used to grim news: death rates, new cases, second waves, surges, spikes, so-called 'Long Covid'.
But an alarming new development in Denmark this week has rather eclipsed the familiar litany of doom. Twelve people in the north of the country are reported to have become infected with a mutated version of coronavirus that they caught from mink.
Denmark is the world's biggest producer of mink fur, with a turnover of some 1.1 billion euros a year. Now it is about to embark on a massive cull of around 17 million mink housed in 1,500 farms.
Naturally the fur industry — which employs 2,500 people — is in uproar over the move, but it appears the Danish government had little choice.
Twelve people in the north of Denmark are reported to have become infected with a mutated version of coronavirus that they caught from mink. Pictured: A mink breeder holds up a mink as police forcibly gain access to his farm
Although the human victims of the mutated mink virus were not severely ill, scientists at the Danish State Serum Institute discovered that the mutated coronavirus appeared to weaken the body's ability to form antibodies against it. 'The new strain has showed diminished sensitivity towards antibodies,' the researchers warned.
This could threaten the effectiveness of any future vaccine against the Covid-19 virus. In other words, even if the human immune system defences are bolstered by a new vaccine (or by naturally-produced antibodies to Covid-19), we may well not be immune to the new mink-mutated version.
So, are we witnessing the start of a frightening new chapter in the story of Covid-19 in which the virus proves it can mutate into multiple new forms that infect pets and livestock, then come back to re-infect humans all over again?
Possibly. It was back in April that virologists at Erasmus University in Rotterdam first came across cases of the coronavirus jumping from humans to mink and back again. This is a process known as zoonosis.
Denmark is about to embark on a massive cull of around 17 million mink housed in 1,500 farms. Pictured: Employees from the Danish Veterinary and Food Administration and the Danish Emergency Management Agency wearing protective equipment work to kill minks in Gjol, Denmark
In evolutionary terms, switching between species, intermingling with other viruses and 'swapping' genes, is a way for any virus to ensure its survival by constantly confounding the immune systems of its host — animal or human.
When I raised the prospect of this threat with one of Europe's foremost virology experts, Simon Wain-Hobson, of the Pasteur Institute in France, he said: 'If anyone isolated a novel coronavirus from such a mammal, then I'd gulp.'
Well, this week it was the turn of the Danish prime minister Mette Frederiksen to gulp.
When she announced the cull, she said that unless prompt action was taken the mutated mink virus might have 'devastating consequences worldwide'.
Denmark is not the only country forced to take action. In June, authorities in the Netherlands began gassing tens of thousands of mink because of coronavirus infection.
A month later, Spain culled 100,000 mink after cases were detected at a farm in the Aragón province.
Neither cull is believed to have eradicated the problem, but evidence shows the Danish didn't catch their mink pandemic from either the Dutch or the Spanish.
Theirs appears to be an entirely separate outbreak, which demonstrates how the problem of human-animal-human infection can occur again and again.
Naturally the fur industry — which employs 2,500 people — is in uproar over the move, but it appears the Danish government had little choice. Stock picture.
History shows that viruses which evolve in animals and jump species to infect humans are among humankind's most dangerous and enduring foes.
Pandemic flu, for example, originated in poultry and pigs. Measles came originally from cows.
Newly-emerging killers such as Ebola, SARS and Covid-19 came from bats. Once the viruses learn how to 'shape-shift' in this way, they can go on to acquire even more lethal powers.
The concern comes down to this: when the virus jumps from humans to other animals, it can effectively learn deadly new tricks that may make it more infectious, more deadly and might enable the virus to defeat the best drugs or vaccines. This learning process is called 'viral recombination'.
It happens when two different virus strains infect the same animal cell, co-mix, then produce new viruses that have some genes from both 'parents'.
Thus, instead of finding a vaccine to defeat Covid-19 once and for all, we could end up playing an endless game of smack the rat (or cat, or mink, or bat, hamster, ferret, or macaque — they've all been found Covid-infected), as the virus continuously mutates, shifts species then returns to re-infect us again.
It is in intensive farming — such as the mink industry — that this threat becomes most alarming.
When a virus spreads rapidly through a large, dense pop- ulation (animal or human) it can evolve into ever-deadlier forms even faster.
Because, in this situation, it does not matter if the virus kills its host extremely quickly (and so reduces its own chance of survival) — it can easily jump across to another of the same species, and simply claim victim after victim in a vast murderous spree.
In September, Dutch virologists warned in the online journal bioRxiv that their evidence indicated the mink virus has indeed been evolving more quickly than it had done inside humans.
Urgent studies are now under way to find out how and why mink have been able to catch and spread the infection.
So should we be worried here in the UK? Where farmed mink are concerned, Britain might, at first glance, appear to be immune.
After decades of animal-welfare protests, Parliament banned all fur farming in 2000. By that time, only 11 mink farms were still operating here, producing about 100,000 pelts annually.
However, escapes of American mink from fur farms meant that the animals have been breeding here in the wild since the late 1950s. By 1967, the species had become established in half of England, Wales and lowland Scotland.
This is hardly a surprise, because once mink break out they are notoriously hard to contain, not least because they are such powerful swimmers.
They can devastate entire populations of ground-nesting birds and water voles.
In recent years, though, the UK Mammal Society says UK wild mink numbers have fallen significantly. This is probably thanks to the fact the carnivores have hunted their favourite prey, the water vole, to near extinction.
Disturbingly, however, evidence already shows it is not only mink that are implicated in this doomsday cycle of human-animal-human infection. Some of our closest and most beloved companions may become involved.
A study presented to the European Society of Clinical Microbiology and Infectious Diseases by scientists at the University of Guelph in Ontario, Canada, suggests that a large proportion of pet dogs and cats may already have caught Covid-19 from their owners.
The study, revealed in September, showed that in households where humans had caught Covid-19 and survived, the pets also had high levels of Covid-19 — as evidenced by antibodies in their blood.
Some 88 per cent of cats and 20 per cent of dogs examined for the study tested positive.
Similarly, a report in the journal Emerging Infectious Diseases says that researchers in Hong Kong who tested 50 cats from Covid-19 infected households found that six cats tested positive for it.
'Feline-to-human transmission is theoretically possible,' the researchers warned.
We now know from Denmark's experience with mink that the virus can learn to evolve and reinfect humans in a genetically altered state.
How long before regular infection of companion animals such as dogs and cats enables Covid-19 to learn whole new levels of terrifying abilities?