A highly contagious virus known as Highly Pathogenic Avian Influenza, or the bird flu, has spread among poultry flocks and affected around 112 million birds since February 2022.
Though the bird flu primarily affects poultry, it has been spreading throughout the dairy cattle industry. Common symptoms for poultry include sudden death with no apparent illness, lack of energy or appetite, decrease in egg production, stumbling or diarrhea — however, poultry flocks can also be asymptomatic.
The U.S. Department of Agriculture (USDA) monitors the amount of commercial and noncommercial bird operations that have been exposed to the bird flu. As of Monday, 21 Wisconsin counties, including southern Columbia, Rock, Sauk and Jefferson counties, have reported cases of bird flu, affecting a total of around 3.6 million birds since March 2022.
Among those affected are 17 commercial flocks and 19 backyard flocks in Wisconsin, according to the USDA. All commercial operations were or are being quarantined.
The Wisconsin Department of Natural Resources (DNR) monitors bird flu in wild bird and waterfowl populations. In some cases, wild birds and waterfowl carry the illness within their gastrointestinal tract without showing signs of sickness, while rare strains can cause severe disease. Symptoms for wild birds and waterfowl include sneezing, coughing, nasal discharge, falling, tremors, circling, abnormal head positions, diarrhea or green colored feces.
The risk of humans contracting the virus without animal contact is quite low, according to the U.S. Centers for Disease Control and Prevention. People exposed to infected or potentially infected animals, or in environments with possible virus exposure, are at higher risk for contracting the bird flu. The current risk of contracting the bird flu for the general public is low, and no human cases have currently been reported in Wisconsin.
The first case of avian influenza in dairy cattle in the United States was in March of 2024, and now 15 states and 695 dairy herds have been affected. The first human infection transmitted from a dairy cow in the United States was in April of 2024. There have been 57 total cases of human infection since April, with 34 of those cases being from cattle alone.
Human symptoms can range from mild eye infections and upper respiratory symptoms to more severe pneumonia and death. Humans can contract the virus through the nose, eyes or mouth by contact or breathing of air droplets, infected feces, saliva, mucous or touching areas with virus droplets and then touching themselves.
The bird flu can also spread to other mammals outside the dairy cattle industry including red foxes, otters, minks and bobcats. These mammals are at risk for ingesting the illness because they scavenge or hunt for birds.
The best way to prevent the spread of bird flu is through biosecurity measures, such as reducing visitors, washing hands frequently, wearing disposable boot covers or foot baths, changing clothes before and after exiting flocks and cleaning tools.
