Avian flu spreads among animals; disregarding it may put humans at risk.
As the co-founder of Wild Instincts animal rescue in Wisconsin, Naniot and his team faced challenging times that summer, with increasing rounds of disinfection and wearing protective gear while caring for sick and wounded animals. Their efforts were directed towards three infectious diseases which were rampant in the region - Covid-19, chronic wasting disease in deer and the highly transmissible H5N1 bird flu.
Covid-19 was still making life difficult, and the chronic wasting disease was proving to be a significant issue for the rescue team. Yet, it was the H5N1 bird flu that raised the biggest concerns. This virus, discovered in 1996, has shown a unique ability to evolve and attack various species, causing the deaths of millions of birds, and now it even spans 26 different animal types, including cats, house mice, and cows.
In April, the World Health Organization chief scientist, Dr. Jeremy Farrar, described H5N1 as “a global zoonotic animal pandemic” due to its rapidly expanding world of animal victims. Although the virus has been known to infect humans, we are not its primary target. This could swiftly change, though, as "influenza makes mutations at a higher rate than a coronavirus like SARS-CoV2," explained Dr. Jesse Bloom, a computational biologist focused on influenza viruses at the Fred Hutch Cancer Center in Seattle. Mutations don't usually benefit the virus but when one does, it can create an advantageous version of the virus, allowing it to continue spreading.
Flashback to a few months ago; Naniot had never encountered a situation involving young foxes. The team discovered these baby foxes to be unwell, with signs pointing to some form of poisoning. However, it was during their examinations that they witnessed violent seizures in the foxes, lasting as long as 30 seconds. As time passed, these seizures became more severe. Naniot assumed the foxes could have been exposed to the mysterious poison, but he was surprised when the foster mother showed similar symptoms. It was then that he recognized the signs of H5N1 bird flu from his previous encounter with affected wild birds. He continued his research and discovered that foxes had become susceptible to H5N1 after consuming infected dead birds.
Naniot was shocked to see how quickly the virus was wreaking havoc amongst the baby foxes. A sad outcome considering the struggle they had saved these young animals from. Over the course of days, their condition deteriorated until they succumbed to the virus. After witnessing the extent of the damage done by this virus, Naniot became more aware of its potential consequences for humans, since our immune systems were not prepared for such an attack.
Although H5N1 has infected nearly 900 people in the last 30 years, these cases have been isolated and predominantly displayed flu-like symptoms. Humans are not the intended host for this virus. Still, its ability to mutate and adapt has experts like Dr. Scott Weese, a veterinarian specializing in zoonotic infections at the University of Guelph, keeping a close eye on its evolving form. He explained the potential for a new viral strain to emerge which could be more readily transmittable among humans, going on to name some precedents like a few outbreaks in the United States. In each case, there were known infections but no further transmission. These are called "dead-end infections," where the virus eventually dies off in the human host and doesn’t spread any further.
The story highlighted the frequency of mutations in H5N1 compared to other viruses like SARS-CoV2. The virus has proven to be more fluid in its range of infection and efficacy on different species. The unpredictability of its actions signals a possibility for it to evolve more and further threaten or impact humans eventually.
Naniot's experience in the animal rescue field spanned over three decades. The incident with the foxes changed his perspective about its deadliness and how easily it might adapt to infect humans. He came to learn that humans are in fact in its cross-hairs, and the situation calls for thorough surveillance and protection against the virus.
By utilizing a strain of H5N1 from the recent cattle outbreak, researchers have confirmed that this particular version of the virus has a low probability of spreading through the air. In an experiment with ferrets, the gold standard for studying human viral transmission, the US Centers for Disease Control and Prevention grew and experimentally infected six ferrets with the same H5N1 virus taken from a sick farmworker in Texas. Afterward, three healthy ferrets were placed in the same enclosures as the sick animals, allowing them to touch, nose, and lick the sick ferrets. Consequently, all three of these healthy ferrets became ill as well.
The CDC then conducted airborne transmission tests by housing three healthy ferrets in enclosures where they could only breathe the same air as the sick animals. This allowed them to study how the virus would spread through the air if it were adaptable to this method. Only one of these healthy ferrets acquired the illness, suggesting that the virus found in the current cattle outbreak is not well-suited for respiratory transmission.
Thus far, this outcome seems to be reflected in real-world occurrences. Though the virus has infected over 80 dairy herds in at least 12 states, the number of human infections appears to be low, with limited testing to confirm this statistic.
The initial ferret tests are considered positive news by the CDC since it implies the virus would need to undergo significant alterations before it could efficiently spread from person to person via airborne droplets. The agency has plans to repeat these experiments.
However, it's important to note that circumstances can change rapidly. As the Covid pandemic has shown, the virus may evolve in ways that facilitate its entry into human cells.
Doctor Rick Bright, an immunologist and the former head of the US Biomedical Advanced Research and Development Authority, emphasized this during an interview with Dr. Sanjay Gupta for the Chasing Life podcast. He highlighted that these early findings only represent a snapshot of the current situation and stressed that viruses can quickly adapt and spread.
Dr. Erin Sorrell, a virologist and a senior scholar at the Johns Hopkins Center for Health Security, noted that humans have been exposed to seasonal flu strains, primarily H1 and H3, which aid in building immunity. However, H5N1 would present the body with a vastly different virus.
“Our existing immunity to H3 and H1 isn’t necessarily going to protect us against exposure to an H5 virus,” said Dr. Sorrell.
The CDC's study also garnered some alarming discoveries. Unlike seasonal flu, which makes ferrets sick but doesn't kill them, H5N1 killed all the infected ferrets.
"While the three cases of A(H5N1) in the United States have been mild, it is possible that there will be serious illnesses among people," the CDC noted in the study's conclusions.
Since the first detection of a human H5N1 infection in 2022, 24 cases have been reported globally. The spectrum of severity spanned from severe or critical cases (14) to seven fatalities, six mild infections, and eight cases with no symptoms.
Meanwhile, Dr. Seema Lakdawala, a microbiologist and immunologist at Emory University who specializes in the flu, believes there's potential for partially-protective previous exposures to seasonal flu strains. However, she has yet to examine any of the strains in relation to the current cattle outbreak.
Although antibodies may not be readily available to combat an H5 infection in most people, memory cells exist in the body that may identify portions of a new flu virus and react accordingly. Overall, vaccination remains a crucial tool for enhancing our immune system's readiness to counter flu viruses.
Currently, the Centers for Disease Control and Prevention (CDC) deems the risk of H5N1 influenza to the general public as minimal. Nevertheless, individuals who interact with infected animals carry a higher risk and must take extra safety measures, such as wearing protective clothing and practicing careful hygiene to protect themselves from falling sick.
Both ASPR and USDA have provided said protective equipment to states for their usage on farms. Moreover, USDA has also allotted extra funding for farms to assist them in safeguarding their livestock from contagion.
For now, usage of this protective equipment remains voluntary. However, concerns about its usage in summer, when scorching temperatures break records, persist. The complete gear - coveralls, apron, mask, eye protection, head covering, gloves, and boots - may not be feasible for farm workers during this time of year.
To combat this issue, the government is working on the development of a speedy test to detect H5N1.
According to Bright, the seriousness of symptoms may vary depending on the amount of virus that a person is exposed to when infected. Both humans and animals can contract the illness. Touching contaminated milk or touching a deceased bird might result in milder symptoms. In contrast, a substantial intake of the virus, as is the case with certain animals that feed on carrion or some people in specific countries who consume dishes made with duck blood, can cause a severe infection.
“H5N1 virus tends to infect a variety of internal organs rather than just the lungs, as most influenza viruses do. It has been identified in the brains, spleens, intestines, heart, and across an animal’s body,” Bright stated.
Richard Webby, who leads the WHO's Collaborating Centre for the Ecology of Influenza in Animals and Birds at St. Jude Children's Research Hospital, shares this viewpoint.
“H5N1 is one of the most concerning viruses,” he remarked, pointing to the fact that it targets neurons, making it "neurotrophic." “It causes very severe illness.”
H5N1-infected animals frequently behave abnormally or aggressively. For instance, ducks wander in circles, twist their necks, and writhe on the ground.
Webby desires that humans do not experience such symptoms:
“I don't even want to consider it happening to humans,” he said.
So far, the virus has not developed the necessary alterations to become a pathogen that can transmit between humans, according to Michael Osterholm, the head of the Center for Infectious Disease Research and Policy at the University of Minnesota. Despite witnessing significant changes in the virus over the last few decades, he is yet to observe evidence that it'll become one that infects humans and is subsequently passed on to others.
Naniot, the Wisconsin animal rescue's founder, attempted to save around seven infected fox kits in the summer of 2022 but failed as all of them perished.
Rescue organizations in their network reported some foxes had survived the illness but ultimately suffered blindness.
Despite the arduous safety procedures, Naniot is grateful they prevented the virus from further spreading, not only among other animals but also among his team.
"It's akin to when Covid first emerged - it started somewhere," he said.
H5N1 hasn't resurfaced in Naniot's territory since 2022, but he vigilantly monitors the news for any signs of cow herds contracting the disease.
“This disease spreads like wildfire,” Naniot noted.
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Despite the H5N1 bird flu not being its primary target, Dr. Jesse Bloom noted that its rapid mutation rate could lead to an advantageous version of the virus, potentially putting humans at risk.
Even though foxes are not the intended host for H5N1, Naniot's experience with sick baby foxes highlighted the threat the virus poses to various animal species and, by extension, to humans as well.
