Bird Flu Found To Invade The Brains Of 50 Mammal Species, Alarming Experts

Scientists have found that avian influenza has now invaded the brains of a multitude of mammalian species.

Now known to infect more than 50 different mammal species, the number has significantly increased from the roughly a dozen species documented in previous outbreaks.

In the spring of 2022, veterinary pathologist Betsy Elsmo, from the University of Wisconsin–Madison, was alerted by wildlife authorities in Wisconsin to observe a concerning phenomenon – a group of red foxes who displayed unusual neurological symptoms such as seizures, tremors, lack of coordination and boredom.

Contrary to expectations, tests for common pathogens like canine distemper virus and rabies (typical causes of such symptoms), came back negative. However, further investigation revealed a red fox kit tested positive for influenza A. Elsmo explained how examinations of the Wisconsin kit’s tissues under the microscope revealed lesions in the brain, lung and heart that matched what had been seen in the Netherlands animals. She recalled, “And I thought, ‘I think it is [bird flu].’”

“I was surprised,” Elsmo remembered, “and to be honest, at first I kind of wrote it off.” However, she re-assessed when a veterinary technician from the rehabilitation center shared a study that identified cases of avian influenza in red foxes in the Netherlands.

Further tests confirmed the diagnosis in other affected foxes; the animals had contracted a lethal strain of H5N1 avian influenza that had emerged in Europe in late 2020 and had since spread globally. At the time the infections were discovered in the Wisconsin red foxes, this highly pathogenic H5N1 strain had already expanded its reach into North America.

Since the arrival of bird flu on North American shores in December 2021, it has infected a diverse range of mammals, such as polar bears, skunks, sea lions, bottlenosed dolphins and cows.

Since 2003, there have been 891 reported cases of H5N1 infection in humans, with about half of those cases resulting in fatalities, according to the World Health Organization. In the current outbreak, 15 people have been infected with the strain that has caused widespread harm to mammals, with four people developing severe disease, including 2 cases of pneumonia, and at least one death.