It never left, but now avian flu is making a comeback after the discovery of a rare mutation of the H5N1 virus which, in a mink farm in northeastern Spain, in Galicia, caused the first mammalian transmission to mammal under controlled conditions.
Previously in New England there had been another epidemic among mammals, but in seals, therefore in wild animals that are difficult to study and control.
The outbreak in mink dates back to October 2022, but research describing it has now been published, along with analysis of the genetic sequence of the virus.
However, the data indicate that the virus has not acquired the ability to be transmitted to humans.
"Up until now, the H5N1 virus had only made sporadic jumps in the mammalian population", but that of the mink farm in Galicia "is a significant case because, based on the data collected, the virus has spread within the farm , between mammal and mammal", Isabella Monne, of the Istituto Zooprofilattico delle Venezie, author of the article with colleagues Bianca Zecchin, Alice Fusaro, Francesco Bonfante, Edoardo Giussani and Calogero Terregino told ANSA.
The first signature of the research is Montserrat Agüero, of the Central Veterinary Laboratory of the Spanish Ministry of Agriculture.
The virus found in Galicia belongs to the family responsible for the current avian epidemic in Europe, indicated with the initials 2.3.4.4b, and the T271A mutation, found in the PB2 gene of the virus, has become a special watch.
"In this case - continues the researcher - an intensive mammal farm came into contact with a virus after infection events in wild birds and there was transmission within the farm".
"It is an event that reminds us that avian flu must be treated as a problem that can affect other species. Also from an ecological point of view - she adds - it is extremely important because a lethal virus in wild birds implies a loss of biodiversity ".
This is indicated, for example, by the Australian black swans decimated by the
avian flu, as denounced by the article published recently in the journal Genome Biology.
"It's one of too many examples," notes the researcher.
The difficulty is being able to block the virus that circulates among wild species to prevent the leap of species, i.e. that the virus acquires the ability to infect new species to ensure survival: after birds, mammals, up to humans.
Other mutations were also found in the breeding in Galicia, "of which we do not know the meaning".
The good news, Monne adds, is that "no mutations capable of transmitting the virus from one man to another have been identified".
It is a different case from the one that in 2003, in a chicken farm in the Netherlands, had caused at least 83 passages of the virus from animals to humans, but no transmission from man to man.
Even the virus circulating then was very different from the one seen in Spanish breeding.
"So far there have been very rare sporadic cases in humans, all related to direct contact with infected animals," notes the researcher.
The most recent occurred in 2021 in Great Britain and
Surveillance is a must, the researchers write in the paper.
The reports are frequent and also in France the avian flu virus since the summer of 2022 has forced the reduction of 4.6 million polii.
"The more the virus continues to circulate, the more it has the possibility of finding new hosts. Type A influenza viruses - notes Monne - have a higher evolutionary frequency: they are interested in adapting to as many hosts as possible".