As the highly pathogenic avian influenza virus, or H5N1, continues to make headlines globally, the question on everyone’s mind is: How worried should we be?
While the virus is evolving, we are not facing an immediate pandemic but must remain vigilant, say experts at USF Health, as they evaluate the virus’s potential to mutate and spread and the response plans needed to stay prepared.
"Recent reports show H5N1 mutations in mammals, indicating the virus is adapting," said Sten H. Vermund, MD, PhD, dean of the USF College of Public Health and chief medical officer of the Global Virus Network (GVN). "H5N1 is a serious threat due to its pandemic potential and its history of high virulence. While we are relieved that the current outbreak in North America has been less pathogenic, we do not know if this will continue."
Dr. Sten Vermund
Last year, the Global Virus Network, now internationally headquartered at USF, hosted three panel discussions about H5N1, and it plans to host more in 2025.
For now, human cases of H5N1 remain rare, but there have been a few concerning reports in 2024. Already this year, the Louisiana Department of Health reported a patient who died after being hospitalized with H5N1. The patient was over 65 and had chronic health conditions. Although H5N1 has a high potential mortality rate in humans, the virus has yet to spread easily between people, with most cases remaining isolated.
Some cases in people have been linked to domestic dairy cattle and cows in North America, while other isolated cases—mostly mild—have been reported in pediatric patients along the Pacific coasts of Canada and the U.S. According to the U.S. Department of Agriculture, in the last thirty days, there were 184 new confirmed cases in cattle in two states, California and Texas.
H5N1 remains a major threat to poultry and wild bird populations, leading to large-scale culling of domestic fowl in many countries over the past few years to control outbreaks and reduce economic losses. The virus has caused a dramatic rise in bird infections worldwide, particularly in Asia, Europe and North America, throughout 2022 and 2023.
Surveillance programs are key to tracking both animal and human cases of H5N1, said Christian Bréchot, MD, PhD, director of the Microbiomes Institute and senior associate dean for research in global affairs in the USF Health Morsani College of Medicine, as well as vice chair of the board of directors and president emeritus of the GVN.
"Through our One Health programs, we are monitoring the virus closely," Dr. Bréchot said. "Countries are already stockpiling vaccines and antivirals in case of future human outbreaks, and we know that rising temperatures and shifting migration patterns could help the virus spread even further."
Dr. Christian Bréchot
Researchers at the GVN are working to develop a universal flu vaccine that would protect against a range of flu strains, including H5N1. While this experimental vaccine holds promise, it is still in the early stages of development and is not yet available to the public. Until that breakthrough comes, Dr. Vermund recommends vaccinating farmers and range workers, who are at a higher risk of exposure to H5N1, with currently available vaccines that protect them against more common strains of flu.
“If an infected poultry, dairy or cattle worker were to be simultaneously infected with a human adapted flu strain, the reassorted virus could have the ability to spread human to human. An aggressive vaccination effort among exposed workers is advisable,” said Dr. Vermund.
For those who do get sick with the virus, there are treatments available that can help lessen the severity of the illness. Medications like oseltamivir (taken orally) and zanamivir (inhaled) are neuraminidase inhibitors that can reduce symptoms and slow the virus's progress if given early. Another option, baloxavir, targets a key enzyme that the virus needs to replicate, which may also help blunt the impact of H5N1.
"These treatments offer hope, but the path to controlling H5N1 is still complex," said Dr. Bréchot. "We need continued research, effective vaccination programs and reliable treatments to ensure we’re fully prepared for any potential outbreaks."
Both Dr. Vermund and Dr. Bréchot agreed that the real concern lies in whether the virus will mutate to become easily transmissible between humans. The virus has already shown it can infect a variety of mammals, including land-based and marine animals, and further mutations are almost inevitable. These changes, already involving animals like dairy cows, juvenile goats, cats and even dogs, could lead to greater risk for human health. It is atypical to see H5N1 in so many species.
“We also recommend a decentralized surveillance strategy to help global health officials better understand the scale of the outbreaks and better advise where mitigation measures are needed most,” said Dr. Bréchot.
Comprised of experts from around the world, including those at USF, the GVN is pushing for better surveillance, early detection and swift vaccine and treatment deployment. The reality is that the situation is constantly evolving—and staying ahead of it requires global cooperation and continued investment in science.
In the meantime, Dr. Vermund and Dr. Bréchot emphasized the importance of being prepared and keeping a close eye on developments. Our vigilance today could prevent a much larger health crisis tomorrow, they said.
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