Kimberly Dodd is the dean of the Michigan State University College of Veterinary Medicine, and the former director of the Michigan State University Veterinary Diagnostic Laboratory, or MSU VDL. Dodd is an expert in laboratory diagnostics and outbreak response for emerging infectious diseases.
The MSU VDL is a member of the National Animal Health Laboratory Network, an organization serving as the first line of testing for high-consequence animal disease outbreaks. As the only laboratory in Michigan approved by U.S. Department of Agriculture to test for highly pathogenic avian influenza, or HPAI, in any animal species, the MSU VDL has tested more than 27,000 specimens and performed more than 35,000 tests for HPAI since the beginning of the outbreak in early 2022.
In April 2024, shortly after HPAI was detected in dairy cattle in several states including Michigan, Dodd answered questions about what the public should know about avian influenza and the role of the MSU laboratory. Here, she shares the latest information about the currently circulating HPAI virus, classified as H5N1, and answers new questions.
What is highly pathogenic avian influenza?
Avian influenza viruses are continually circulating in wild bird populations, especially waterfowl. Poultry exposed to these viruses may become ill, and the severity of illness in poultry determines if the virus is classified as HPAI, highly pathogenic avian influenza, or low pathogenic avian influenza, LPAI. The avian influenza outbreak that started in Michigan in early 2022 is associated with high mortality in poultry and has been classified as HPAI. Given the broad host range of this virus, it is referred to by its subtype, H5N1.
Why is it still in the news?
As I mentioned last time, this HPAI outbreak is unusual in both its scale and scope. In February, it will be three years since the first detection of H5N1 in Michigan poultry. Early in the outbreak, we discovered that the virus was infecting wild mammals in addition to birds, mainly juvenile carnivores and scavengers. Later, high mortality in marine mammals with close contact with infected wild waterfowl was observed. Last March, nearly a year ago, H5N1 was identified as the cause of illness in dairy cattle in Texas and several other states, including Michigan. Since then, we have seen infections in dozens of domestic cats. Last, but certainly not least, there also have been dozens of human cases and now one human death associated with H5N1 infection.
How is this affecting commercial and backyard poultry flocks?
Since the beginning of the outbreak in 2022, nearly 135 million domestic birds have been affected in all 50 states. These detections have occurred in more than 600 commercial flocks and over 700 backyard flocks. In Michigan alone, more than 7 million birds have been affected.
Since late December, Michigan has had several new detections in commercial facilities and backyard flocks. Detections in commercial flocks create additional testing demands because a confirmed positive premises triggers required surveillance testing of nearby facilities to ensure they remain negative. In addition, permits with evidence of negative test results are required to move birds or products off nearby premises.
Personnel at the MSU VDL stepped up to meet these testing needs over the last few weeks, including the winter holidays. We expect this increased demand to last at least through early March, with personnel frequently working seven days a week.
What’s happening with dairy cattle?
As of early January 2025, there have been confirmed cases in more than 900 herds in 16 states. In Michigan, 30 cattle herds have been confirmed. While Michigan received attention in the spring as we found many herds early on, the focus is now on California, which has been hit particularly hard with more than 700 affected herds.
Experts nationwide, including researchers at the MSU College of Veterinary Medicine, continue to monitor herds and are working to more fully understand the disease in, and modes of transmission among, cattle. Even though cows are not severely affected by the virus, controlling the spread of the disease as much as possible will help not only to protect highly susceptible species such as domestic poultry but also provide fewer opportunities for the virus to adapt and develop mutations allowing it to infect or be transmitted by other species.
To help understand the virus’s spread, the USDA partnered with state veterinarians across the country to implement a National Milk Testing Strategy. Michigan is one of six states included in the first round of states brought into the testing program. Milk from all Michigan dairies will be tested monthly, and testing for this program began at the VDL in December.
And cats? Should pet owners be concerned?
Although we previously knew that avian influenza viruses can infect cats, it appears that cats are particularly susceptible to the currently circulating H5N1 virus. Dozens of cats — house cats as well as captive and wild big cats — have been infected during the current outbreak with most of those cases occurring after the outbreak began in dairy cattle.
Pet owners are encouraged to limit contact between pets and wild birds as well as ill livestock and environments that could be contaminated with the virus. Some recent cases in domestic cats have been linked to feeding raw, poultry-based diets or treats, and the American Veterinary Medical Association advises owners not to feed pets unpasteurized milk or raw or undercooked meat.
Possible signs of infection include any or all of the following: neurologic signs, such as lack of coordination, inability to stand, tremors, seizures, blindness; significant nasal or ocular discharge; rapid, shallow or unusually heavy breathing. Risk factors for infection include exposure to sick or dead livestock or wildlife, eating raw meat or unpasteurized dairy products, or exposure to people who have been on affected farms or working with infected animals.
Owners whose pets display these signs and have these risk factors should contact their veterinarian immediately.
Is anyone tracking how this might affect human health?
Local, state and federal agencies are working together to closely monitor infections in humans and animals. Every animal sample tested at a diagnostic laboratory that is suspected of containing the virus is sent to the USDA’s National Veterinary Services Laboratory for genetic sequencing to monitor the virus for any mutations that would make it more adapted to human transmission. Experts are using a One Health approach to track this virus over time and to look for any indications that the risk to humans is increased. To date, the Centers for Disease Control and Prevention considers the public health risk to be low.
With all this testing being done at the MSU VDL, what precautions are laboratory personnel taking to prevent the spread of the virus?
We know that the virus can live on surfaces, like shoes for example, and be transferred from one environment to another by people and equipment. To help prevent potential environmental contamination, we have a curbside sample pickup system in place. Personnel who collect these samples wear PPE and are trained for safe sample receipt and handling. All H5N1 testing is performed in our biosafety level three laboratory. This area requires additional PPE to protect personnel and structural features like negative air pressure and HEPA filters to provide biosecurity.
In conclusion, this is a complex and evolving animal disease outbreak, with implications for public health. The MSU VDL continues to work closely with state and federal agencies to provide rapid diagnostic testing to identify infected birds and animals. The longer H5N1 circulates in animal populations, the more likely it is to become more transmissible among animals, potentially including humans. In addition to the diagnostic work at the VDL, College of Veterinary Medicine researchers are working with colleagues nationally to better understand the dynamics of the virus in cattle to inform strategic efforts to curb the spread of the virus.
