The mink are mammals and hence the alarm that has been unleashed worldwide when a study has determined that the mink that fell ill and died from hemorrhagic pneumonia on a Galician fur farm (in Carral, A Coruña) were affected by the mink virus. avian influenza A H5N1, which would have jumped from wild birds to these animals, in which it would have mutated.
The SARS-CoV-2 coronavirus has taught us something about mutations and pandemics, and in this case there are reference points that justify concern: the influenza virus (H1N1), for which the WHO declared a moderate pandemic in 2009. In addition, the current A bird flu outbreak in Europe has forced the culling of more than 50 million poultry, and in autumn seagulls and gannets were found on Galician beaches that had died from this virus.
Mink can contract both avian and human flu, and what worries scientists is that mink act as a vehicle for transmitting a flu virus that is very serious, or even fatal, to people. Eurosurveillance, a European journal on surveillance, epidemiology, prevention and control of infectious diseases, has revealed that the A H5N1 influenza virus detected at the Carral mink farm in October presents a rare mutation. As a result of the outbreak, 51,986 mink have been slaughtered. The 12 farm workers have been in quarantine, but luckily none of them have been affected by the virus.
The outbreak began in early October, when an increase in mink mortality was detected, which led the farm’s clinical veterinarian to collect samples from the affected animals, which were analyzed at the Algete Central Veterinary Laboratory (LCV). , under the Ministry of Agriculture, where they tested negative for the SARS-CoV-2 coronavirus, but positive by real-time RT-PCR for the HPAI A (H5N1) virus. After confirming the presence of the virus on the farm, on October 18 the animal health services ordered the slaughter of the minks and the farm was also disinfected.
A mutation with possible implications for public health
“The viruses detected in the mink farm are distinguished from all H5N1 clade 2.3.4.4b viruses characterized so far in the avian population in Europe because they have a rare mutation (T271A) in the PB2 gene, which may have implications for public health. In fact, the same mutation is present in the avian-type PB2 gene of the 2009 pandemic influenza A (H1N1) virus of swine origin”, indicates the report in which the Istituto Zooprofilattico Sperimentale delle Venezie, the laboratory of reference for avian flu in Europe, the Central Veterinary Laboratory of Algete and the Xunta.
The outbreak at the mink farm shows that the virus can mutate and be transmitted rapidly between mammals, which is why the Ministry of Health has asked for “extreme precautionary measures”
The origin of the outbreak is still unknown, but it is suspected that it could be linked to the wave of H5N1 virus infections in wild birds that were found sick or dead on the coasts of A Coruña and Lugo just before the mortality rate increased in the minks of this farm. And it is that, as the report says, “no cases of AI were reported in poultry farms that supply poultry by-products. (…) This hypothesis is further supported given that the minks were raised in a partially open building and may have been in contact with wild birds.”
The document also adds that “the A/gull/France/22P015977/2022-like genotype has been diagnosed in multiple species of seabirds across Europe, including common gannets and gulls, which were the species involved in the mortality events.” by H5N1 registered in Galicia in the weeks prior to the mink”.
Influenza viruses that pass from animals to humans
The World Health Organization has warned that the diversity of flu viruses that are passing from animals to people is “alarming.” In 2022, 37 outbreaks of highly pathogenic avian influenza in poultry were detected in Spain alone, the last two on a farm with 150,000 laying hens in Guadalajara and on another with 1,500 geese in La Cistérniga (Valladolid), according to data from the Ministry of Agriculture. At the Guadalajara farm, two workers became infected with the virus, but did not experience symptoms.
Although the virus spreads easily between birds, it is very rare for it to be transmitted from bird to human, and it has not been able to transmit effectively between people, but the outbreak in mink on the Galician farm shows that it is a pathogen capable of mutating and adapting rapidly to move from mammal to mammal, for which reason the Ministry of Health has asked people who have poultry to “extreme precautionary measures”, although the European health authorities consider that the risk of contagion in the general population it is “low”.
He Dr Jeremy Farrar, an expert in emerging diseases and scientific director of the WHO, has alerted the outbreak in Spain on his Twitter account. “The greatest risk for a devastating flu pandemic is that an avian or other animal flu virus infects an intermediate mammal and evolves, transmitting between mammals and between humans, who would have little or no immunity,” says the doctor. British, which also rightly warned of rare pneumonia in the Chinese city of Wuhan on December 31, 2019, and which recommends that vaccines and treatments be developed for each type of animal flu.
Elisa Pérez, an expert virologist in emerging viruses at the Animal Health Research Center, expressed her concern in statements to the newspaper El País: “It is quite scary. In Europe there had never been such an outbreak in mink, there were only a few cases described in China. We had never had such a big scare ”. And she advises that all mink farms be closed as soon as possible, of which some 755 were still active in Europe at the beginning of 2021, according to an EFSA report.
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