Else Beekman
Bird flu is evolving faster than expected and could soon infect humans, warns Spanish virologist Elisa Pérez Ramírez. In a 29 May interview with La Vanguardia, she outlines the alarming spread of H5N1, now infecting cattle in the US, and urges immediate global vigilance.”
Her remarks highlight the urgency of international monitoring and preparedness.
A virus expanding beyond birds
According to Pérez, the H5N1 virus has caused the deaths of an estimated 500 million birds globally. Its spread has been largely underreported and underestimated politically and in the media. The consequences go beyond health: Spain has seen egg prices rise by 25%, just the “tip of a massive iceberg”, she says.
Originally considered a disease confined to poultry, the virus has since expanded its reach. A specific lineage of H5N1 has adapted to new hosts, including seabirds, gulls, and waders, causing mass die-offs.
Mammals at risk: a changing scenario
What worries scientists most is the virus’s increasing ability to spread between mammals. In Argentina’s Península Valdés, 97% of elephant seals in one area died. The virus has now infected dairy cows in the United States, a host never before associated with bird flu.
This, Pérez explains, marks a radical change. “We are not talking about isolated cases. The virus is widespread across more than a thousand farms in 17 U.S. states.” It replicates in the cows’ mammary glands, raising serious food safety concerns.
Growing concern over human infections
Although no human-to-human transmission has been recorded, there have been 70 confirmed cases in the United States, mostly among farm workers exposed to infected birds or cattle. Four required hospitalisation and one person died.
Pérez warns against complacency. “We maintain a very anthropocentric view of health. But hundreds of millions of animals have died. This is a massive biodiversity threat.”
Raw milk and viral exposure
The danger is particularly acute where raw milk is consumed, such as in parts of the U.S., as pasteurisation effectively neutralises the virus. “Drinking unpasteurised milk carries significant risk,” she cautions.
Could H5N1 spread between humans?
According to Pérez, a precise and rare combination of mutations is needed for H5N1 to adapt to human-to-human transmission. “It’s like winning the lottery,” she says, “but we’re giving the virus far too many chances.”
She recalls how the 2009 H1N1 pandemic emerged from a triple reassortment involving bird, swine and human flu strains. Herewith she highlights how quickly things can change.
Lack of attention and political will
Despite the gravity of the situation, public and political attention remains limited, partly due to post-Covid fatigue and, in the U.S., the economic weight of the dairy industry. “If these cattle outbreaks were happening in China or South America, the reaction would be very different,” Pérez notes.
Adding to the concern, the U.S. has not reported any new human cases since February 2025. “It’s unclear if cases have stopped or just stopped being reported,” she adds.
Spain: low risk but close monitoring
Spain has not reported any cases in poultry since February 2023 and is currently considered free of the disease in domestic animals. Two isolated detections in wild birds have occurred, but nothing comparable to the major outbreaks of 2021 and 2022. In 2025, the first involved a peregrine falcon in the province of Cádiz in March. The second, in May, was identified among wild geese in Don Benito, Extremadura.
Spanish authorities implemented localised biosecurity measures and temporarily restricted the movement and display of poultry in affected areas.
“Europe’s monitoring systems are strong, and the poultry sector is well prepared,” Pérez assures. However, she warns that the real test would be if cattle infections, as seen in the U.S., were to appear in Europe.
Final warning for bird flu threat from the scientific community
Pérez believes science has already provided ample warnings. “The virus has taken a new step every year, birds, sea lions, mink, cats, and now cows. The signals are there. But unless we see major human cases, decisive action seems unlikely.”
Though recent human symptoms have been relatively mild, mostly conjunctivitis and light respiratory issues, the virus has historically shown a mortality rate of around 50% in humans.
The threat remains silent, but potent. And, Pérez says, if it evolves to transmit between humans, no one will be able to claim they weren’t warned.
Sources: La Vanguardia, CadenaSer
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