H5 Influenza is in the news and many swine professionals have questions and concerns around recent outbreaks in dairy cattle and the potential for cross-species spread. We have answers to many of your questions, addressed by Dr. Marie Culhane, one of the UMN Swine Group’s Influenza experts and Dr. Carol Cardona, avian influenza expert and the UMN CVM Pomeroy chair in Avian Health.
Who is at risk of H5 influenza?
All warm-blooded species in the air, on the land, and in the sea
What does H5 look like Dairy and Poultry Workers?
People who had direct contact with clinically infected cows and dying/dead poultry usually
- Did not wear eye protection
- Had conjunctivitis (but no vision change) that resolved in a several days
- Occasionally have respiratory issues
How did they know that they got the flu from the animals?
The public health laboratories sequenced the viruses from the humans. The viruses were the exact same flu as was found in the dairy cows or poultry they worked with.
How many national cases of H5 influenza in humans have their been total?
As of 4-4-2025, 70 humans have been infected with H5 flu with 1 death. There have been 41 cases in dairy workers, 24 in poultry workers and culling operations, 2 with other animal exposure and 3 with unknown exposure sources.
CDC Current situation updates can be found at: https://www.cdc.gov/bird-flu/situation-summary/index.html
Are pigs at risk?
YES
Pigs are HIGHLY SUSCEPTIBLE since they possess all types of flu receptors from nose to lung (Kristensen et al, 2024. Virus Res, 340, 199304. doi.org/10.1016/j.virusres.2023.199304)
Pigs H5 flu challenged with 2 strains of H5 from birds and 2 strains of H5 from mammals. All 4 of the H5 strains infected pigs, some spread, and disease varied (Arruda, B., Baker, A. L. et al, 2024. Emerg infect dis,30(4), 738–751. https://doi.org/10.3201/eid3004.231141)
This is a concern because pigs readily change/reassort the flu virus (Ma et al, 2008, J. Mol. Genet. Med. 3, 158–166, 2008 https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2702078/)
Reassortment provides a shortcut to the dangerous road that leads us to outbreaks in pigs and maybe pandemics. (Peacock, T.P., Moncla, et al. The global H5N1 influenza panzootic in mammals. Nature 637, 304–313 (2025). https://doi.org/10.1038/s41586-024-08054-z)
This virus has been here since 2021, why its not gone yet?
The virus source of the 2021–>2022–>2023–>2024–>2025 outbreak is maintained in wild waterfowl.
Stamping out poultry prevents spread from farms but it will not end the outbreak because the outbreak is no longer perpetuated by that farmed poultry source. There are new sources of virus on the landscape, including dairy cows and numerous wild avians and wild mammal species.
There is currently no end in sight.
How is the virus moved on dairy farms?
- Directly between cows
- Cattle movement between farms
- Wild and peridomestic birds
- Fomites including personnel
- Spillovers in domestic cats and other mammals need to be noted.
How do we control H5 virus when it gets into a farm?
It’s different for cattle farms and poultry farms.
CATTLE:
- State by State
- ONLY lactating dairy cows managed / monitored / SOMEWHAT restricted movements
- Milk from “affected” cows diverted / dumped (where?)
- LIMITED state-shared network notifications
- Processor/milk truck driver finds out on their own
- NOW -National Bulk Milk testing plan
- Led to finding H5 Stearns County MN Dairy
DOMESTIC POULTRY:
- National Plan
- Death (depopulation) to ALL BIRDS on the ENTIRE PREMISES
- Nothing leaves the farm without decontamination (14 TO 30 DAYS)
- Shared maps and transparency between regulatory agencies and producers
- Routing and communication key to control
https://www.bah.state.mn.us/h5n1
https://www.bah.state.mn.us/hpai#hpai-in-ruminants
How do we protect humans?
Protect the Mucosa (Eyes, nose, mouth)
Gloves and handwashing
Wear protections with contact or close exposure:
- Sick, dead birds or other animals
- Feces, milk, litter from sick birds, other animals
What can be done about H5 influenza?
Since the wildlife source of the virus cannot be controlled, the only option is to improve prevention to reduce infections in domestic animals.
Vaccination seems like a good option, but we also need more epidemiology to understand spread into poultry farms so that prevention with biosecurity can be improved.
Where is this going?
Flu is a unique threat. It threatens food security, but we could protect food animals with vaccination and better biosecurity. It can infect humans and could cause a pandemic, but fortunately, we have good medications and vaccine matches (with the WHO). And it can affect wild bird and mammal populations.
What can I do with dead birds I suspect died of avian influenza?
If you’ve found multiple dead birds (five or more of any species) in one place at one time, report the finding to the Minnesota DNR at 888-646-6367. DNR biologists may be interested in recording the possible case to track the virus.
dnr.state.mn.us – Avian Influenza – DNR Response
If the biologists do not need the birds for sampling and you need to move them, wear disposable gloves, double bag the birds and place them in the trash. This will ensure other animals are unable to get to the carcasses and potentially become infected themselves.
- Minnesota DNR, along with its partners, are continuing to monitor for HPAI in wild birds.
- The DNR remains committed to helping inform the larger issue through collaboration with the Board of Animal Health.
- The DNR will also continue to partner with USDA-Wildlife Services to participate in national surveillance programs, as funding allows.
DNR is receiving and addressing sick and dead wild bird reports that are consistent with possible HPAI infections. Individuals can contact local DNR wildlife staff or the DNR information center at 888-646-6367 to report sick or dead birds. Reports of interest include:
- Cases where five or more dead wild birds of any kind found in one location during the same timeframe.
- Sick birds showing neurological signs or that die shortly after exhibiting these signs.
- Wild birds suspected of potentially carrying HPAI will be tested or sent to the National Wildlife Health Center or Minnesota Veterinary Diagnostic Laboratory.
Do you still have questions? Ask them in the comments!
About the authors
Marie Culhane is a veterinarian working with all species, but having a special interest in diseases of food animals. Her research at the University of Minnesota as a Professor of Veterinary Population Medicine involves the pathogenesis and characterization of animal influenza A viruses and the impact emerging viruses may have on current vaccination and control protocols for US animal agriculture. She is also involved in animal disease emergency planning at local, national, and global levels.
Dr. Cardona is an internationally recognized expert in avian health and zoonotic diseases. Her work connects veterinary science, public health, and industry, with a focus on developing effective strategies for managing disease and promoting animal well-being.
Listen to their keynote about influenza at the 2024 Leman Swine Conference.