Hasta ahora, la “gripe aviar” ha afectado a unos 60 millones de aves\u00a0en los Estados Unidos desde principios de 2022 y a decenas de millones m\u00e1s en todo el mundo. Pero si el pat\u00f3geno letal pudiera adaptarse para propagarse f\u00e1cilmente en mam\u00edferos como el vis\u00f3n, los expertos temen que eventualmente pueda hacerlo en humanos.<\/p>\n
Bloody snouts, clumsiness\u2014these were among the signs last October that mink on a Spanish fur farm had a problem. The subsequent identification of the culprit, highly pathogenic avian influenza H5N1, now has health experts warning that humans might also be facing their own problem. So far the \u201cbird flu\u201d has affected about\u00a060 million birds\u00a0<\/a>in the United States since the beginning of 2022 and\u00a0tens of millions<\/a>\u00a0more around the world. But if the lethal pathogen were able to adapt to spread easily in mammals like mink, experts fear it could eventually do so in humans.<\/p>\n Mink are known to be susceptible to human respiratory diseases. And during the COVID pandemic, crowded farms dealt with repeated\u00a0animal outbreaks<\/a>, including some that infected workers. This led to fears that intensive mink farming could spawn dangerous new variants. Likewise, outbreaks of highly pathogenic avian influenza on farms could change the characteristics of a virus that at this point doesn\u2019t transmit effectively among people. In the worst-case scenario, a mutated virus could spark a pandemic; a novel influenza could rip around the world in populations with little immunity. Virologist Elisa P\u00e9rez\u00a0told<\/a>\u00a0the Spanish newspaper\u00a0El Pais,\u00a0<\/em>\u201cIn Europe there had never been such an outbreak in mink before, there were only a few cases described in China. We had never had such a big scare.\u201d P\u00e9rez told the newspaper that mink farms should be closed:\u00a0\u201cWhat else needs to happen?\u201d<\/p>\n According to an\u00a0article<\/a>\u00a0this month in the journal\u00a0Eurosurveillance<\/em>, the mink outbreak of highly pathogenic avian influenza H5N1 in A Coruna, a province in northwest Spain, began near a manure storage area. About 50,000 animals lived on the farm in wire cages in 30 partially open barns. \u00a0Within weeks, the disease had spread across the complex and minks were dying at a rate of over 4 percent, up from an expected rate of 0.2 to 0.3 percent. The spread across the farm indicated \u201cthat an onward transmission of the virus to other minks may have taken place,\u201d the authors wrote. \u201cIt can be assumed that wild birds may have played a major role in the virus introduction into the farm.\u201d<\/p>\n Mink farms, where thousands of animals can share close quarters, could set up a corollary to a controversial experiment conducted more than a decade ago. That\u2019s when a team in the Netherlands mutated highly pathogenic avian influenza H5N1 and infected ferrets with it. Researchers then took samples from those ferrets and used them to infect other ferrets. After several steps like this, the avian virus had evolved to spread through the air between mammals. Scientists on twitter noted that outbreaks on mink farms could similarly allow the avian virus to mutate as it spreads. \u201cSuch outbreaks of avian flu in mink farms are highly suboptimal,\u201d Francois Balloux, a professor at the University College London\u2019s Genetics Institute wrote<\/a>, \u201cas they create natural \u2018passaging experiments\u2019 in a mammalian host, which could lead the virus to evolve higher transmissibility in mammals.\u201d<\/p>\n The World Health Organization\u2019s incoming chief scientist, Jeremy Farrar, tweeted out\u00a0his concern<\/a>, as well. \u201cAvian H5N1 has caused outbreaks in humans with high mortality now found transmit between minks. Risk of evolution in mammals & acquisition of [human to human] transmission,\u201d he wrote.<\/p>\n Isabella Monne, a veterinarian at \u00a0IZSVe, an institute with the Italian National Public Health Service, and one of the authors of the report, told the\u00a0Bulletin<\/em>\u00a0that it\u2019s not likely each affected animal came into contact with wild birds. \u201cWe may assume that the transmission was caused either by direct contact among infected animals or by indirect contact with infected biological materials.\u201d She cautioned that while the infection likely spread on the farm, it\u2019s not yet clear how. \u201cSpecific experimental trials are needed to clarify the transmissibility of the virus and in particular to define the capability of the virus to spread via the aerosol route.\u201d<\/p>\n Minks are raised for their pelts, which are used in fashion. Before the COVID pandemic,\u00a0El Pais<\/em>\u00a0reported, there were some 2,900 mink farms in the European Union. By the start of 2021, that number dropped to 755, as governments ordered culls and closures. But the industry could grow again.\u00a0Denmark announced plans<\/a>\u00a0to import mink from other countries, including Spain, and to allow farming of the animals to resume this year.<\/p>\n No workers were infected at the Spanish farm. Nor did the mink farm viruses have the \u201cmost relevant \u2026 genetic changes\u201d known to make the avian virus better adapted to humans, Monne said. Still, in the midst of what Monne called an \u201cunprecedented panzootic\u201d\u2014a pandemic among animals\u2014of highly pathogenic avian influenza, the farm outbreak qualifies as a red flag.<\/p>\n \u201cThe continuous circulation of the virus poses great risks and may result in more spillover events in mammals. This would undoubtedly cause consequences difficult to predict,\u201d Monne said. \u201cA virus that is able to transmit to mammals needs to be stopped before it may become a matter of public health concern as we learnt from the SARS-CoV2 lesson.\u201d<\/p>\n