The emergence of coronavirus cases in mink populations in at least six countries worries the international community.
A mutated version of the virus would have been transmitted to twelve people in Denmark.
The country has announced the slaughter of its 15 million mink.
Six countries have so far reported cases of Covid-19 in mink farms, the World Health Organization (WHO) said on Sunday.
"To date, six countries, namely Denmark, the Netherlands, Spain, Sweden, Italy and the United States have reported cases of SARS-CoV-2 in mink farms from the World Organization for Animal Health, "the WHO said in a statement.
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The threat looms over vaccine development
The announcement comes after Danish Prime Minister Mette Frederiksen on Wednesday announced the slaughter of all of the country's more than 15 million mink, claiming that a mutated version of SARS-Cov-2, which could threaten the effectiveness of 'a future vaccine, had been transmitted by these animals to twelve people.
The mutation of a virus is trivial and often harmless, according to the scientific community.
But in the case of this strain, called "Cluster 5", it implies, according to the first studies, a lower efficiency of human antibodies, which threatens the development of a vaccine against Covid-19.
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"Initial observations suggest that the clinical presentation, severity and transmission of infected individuals are similar to those of other circulating SARS-CoV-2 viruses," notes the WHO.
"However, this variant, called the 'cluster 5' variant, presents a combination of mutations or changes that had not been observed before", adds the UN specialized agency, stressing that "the implications of the changes identified in this variant are not yet fully understood ".
WHO calls for new scientific studies
Preliminary results, notes the WHO, indicate that this particular variant associated with mink, identified both in mink and in the twelve human cases, exhibits "moderately reduced sensitivity to neutralizing antibodies".
WHO is calling for new scientific and laboratory studies to be set up to verify these results and understand what the consequences could be on the development of treatments and vaccines.
"Although it is believed that the virus is ancestrally linked to bats, the origin of the virus and the intermediate host (s) of SARS-CoV-2 have not yet been identified," recalls the WHO.