Since last October, communities worldwide have faced an unsettling surge in H5N1 bird flu cases. Governments and farmers endured tough losses as about 100 million poultry were culled across nations, a figure reported as three times higher than the previous season. Immunologist and researcher Matilda Canelles from the Scientific Research Council notes growing anxiety among health experts. The World Health Organization currently views the risk of a human outbreak as low, but cautions against complacency because mortality in humans can reach 50 percent.
The H5N1 virus primarily targets birds, including many wild populations. Yet warning signs have intensified as infections have appeared in mammals. In Spain, 2022 saw 37 outbreaks in poultry, according to the Ministry of Agriculture, Fisheries and Food. Beyond domestic poultry, wild and captive birds contributed to the tally, including an October incident at a mink farm in Carral, A Coruña, and a worker on a Guadalajara chicken farm who tested positive for bird flu that month. It remains unclear whether anyone was asymptomatic or carried the virus in their nose, according to Canelles. Just last Friday, alarms rose at a turkey farm in Arbeca, Lleida, signaling a turkey-specific outbreak.
A major concern is the potential for the epidemic to jump from animals to humans. The immunologist notes that the alert was amplified by reports from the United States where more than 200 cases in mammals such as bears and sea lions have been documented. When the virus spreads easily among mammals, the threat of transmission to humans always exists, even though such transmission has not occurred yet.
The Galicia outbreak on a mink farm brought bird flu back into the spotlight for health authorities. A recent intervention and action plan published by the Public Health Commission outlines measures such as a dual tracking system for anyone exposed to infected poultry and mink on a farm, along with the use of personal protective equipment and heightened detection of asymptomatic cases. These steps aim to improve monitoring and control of the spread.
infections among minks
Human infections have typically been limited to farm workers. Canelles notes that years of data showed a decline in cases and the belief that H5N1 does not transmit easily to humans. Yet the current situation has heightened concern because several mammals are now infected. Minks, in particular, are significant since they resemble ferrets, a common laboratory model for studying flu due to their similar immune systems. This similarity makes the mink infections especially consequential for understanding potential human risk.
Researchers are examining whether the Galician outbreak involved inter-mink transmission, or if the infections spread from birds or contaminated feed. Tracing the exact route is challenging because in bird flu outbreaks authorities often cull all affected animals to prevent further spread, which complicates investigations for epidemiologists.
Canelles emphasizes the importance of close surveillance of this epidemic and ongoing monitoring of mink farms. The goal is to determine whether mammals can contract the virus from birds or from one another, and to implement safeguards accordingly. The emphasis remains on vigilant monitoring and proactive measures to reduce risk.
Not the flu A or B
Seasonal human flu, caused by influenza A, remains a separate concern and is managed with annual vaccines. In birds, the illness can range from mild to severe depending on species, but the consequences rise dramatically when it crosses to humans. The mortality rate for bird flu in humans underscores why vigilance matters. If complacency takes hold, severe outcomes could follow, according to Canelles. The World Health Organization reiterates that the risk to humans remains low, though ongoing surveillance is essential as H5N1 has circulated among poultry and wild birds for about 25 years. The WHO director-general emphasizes that recent reports of infections in mink, otters, and sea lions require careful monitoring and follow-up.