A dairy farmworker in Michigan has been found to be infected with H5N1 avian influenza, the second human case of bird flu associated with an ongoing outbreak of the virus among dairy cows, Michigan's Department of Health and Human Services announced on Wednesday.
A nasal swab of the worker tested negative, but an eye swab tested negative. The worker experienced conjunctivitis (an eye infection) but no other symptoms.
The US Centers for Disease Control and Prevention (CDC) stressed that the risk to the public remains low.
The H5N1 subvariant of bird flu has been increasingly reported in cattle in recent months, with 52 cases reported in nine states since March 25.
Last month, a person who had exposure to infected cows in Texas was found to be infected with the H5N1 subtype, with conjunctivitis being their only symptom. The infected person was treated with a flu antiviral drug and recovered.
Health officials have expressed concerns that there may be more farm workers infected who aren't getting tested.
Dr. Barb Petersen, a dairy veterinarian in Amarillo, Texas, told NBC earlier this month that several dairy workers had fallen ill with "classic flu-like symptoms," including high fever, sweating at night, chills, lower back pain, upset stomach, vomiting, and diarrhea. They also suffered from conjunctivitis. These workers were not tested for H5N1 so it remains unclear if they were infected with the bird flu or another illness.
Petersen told Fortune as well that she "had people who never missed work, miss work" on affected farms due to illness.
Gregory Gray, an infectious disease epidemiologist at the University of Texas Medical Branch in Galveston, told NPR earlier this month that he suspects there are at least several cases of farm workers being infected with the virus, as some workers sought medical care for "influenza-like illness and conjunctivitis" at the same time that H5N1 was spreading on the dairy farms.
Bird flu spreads in cats, Australia reports human case
Additionally, four cases of H5N1 bird flu were reported in cats in South Dakota and Michigan recently, according to the World Organisation for Animal Health (WOAH). The two cases in South Dakota involved cats that had no known contact with poultry or dairy cattle. The two cases in Michigan were in contact with dairy cows.
On Wednesday, Australia reported its first human case of H5N1 bird flu in a child who returned to Australia from India in March. The child experienced severe illness but fully recovered. The child was infected in India and the strain of H5N1 flu that the child was infected with was not the same as the one circulating in the US, according to the Victoria Department of Health.
Additionally, on Wednesday, an outbreak of H7N7 bird flu was found on an egg farm near Meredith in the state of Victoria in Australia. The affected farm has been placed under quarantine. Australia experienced an outbreak of H7N7 bird flu from 2020 to 2021.
Australia is the only continent that has not experienced outbreaks of H5N1 bird flu in the worldwide spread of the virus that began in 2021.
Since 2021, Europe and the Americas have been suffering from a nearly continuous outbreak of H5N1 avian influenza, which has been described as "the largest-ever" on the three continents. The virus has affected tens of millions of birds and thousands of mammals worldwide. Outbreaks of the virus have also become more common in Africa and Asia in the past year and have even spread to Antarctica in recent months.
The World Organization for Animal Health (WOAH) noted in March that, while estimates vary, about 485 bird species and 37 mammal species have been infected with avian influenza since 2021. Only the Pacific Islands, Australia, and New Zealand have been spared from the virus.
“The loss of wildlife at the current scale presents an unprecedented risk of wildlife population collapse, creating an ecological crisis,” noted WOAH.