In the latest interstate bird flu outbreak among dairy cattle and poultry, Michigan is reporting the highest number of cases in the country among herds and people. Officials warn the virus is likely spreading through a variety of pathways, including people and vehicles.
To date, bird flu has impacted 25 dairy herds and nearly seven million birds in the state since January, according to the U.S Department of Agriculture. In addition, two Michigan dairy farmworkers also tested positive for the virus following exposure to infected cows.
Public health experts are concerned that the outbreak may be more prevalent.
“We don’t know how more widespread it is,” said Arnold Monto, emeritus professor of epidemiology and global public health at the University of Michigan and co-director of the Michigan Center for Respiratory Virus Research and Response.
“I think one of the reasons why we think we have so much in Michigan is that we’re testing more than most other states.”
The highly pathogenic avian influenza H5N1 virus outbreak was initially identified in Texas earlier this year. According to a recent analysis by the USDA, dairy cattle from an affected herd in Texas were subsequently transported to Michigan, arriving in the state on March 8.
Since then, the Centers for Disease Control and Prevention reports at least 45 people have been tested for bird flu, and 550 people have been surveyed for symptoms across the U.S.
“Based on the epidemiological findings, the majority of links between affected dairy premises, and between dairy and poultry premises, are indirect from shared people, vehicles, and equipment,” stated the USDA report.
The USDA’s investigation found a shared factor between affected dairy herds and poultry flock could be farmworkers who work at multiple affected facilities and share housing with other workers.
The report also found most affected dairy sites use shared vehicles to transport livestock without cleaning before use and that many dairy farms have frequent visitors that could also contribute to transmission spread.
But the verdict is still out on how exactly the virus is moving from farmworkers to animals.
“They think the transmission may be handling or equipment going from udder-to-udder and not the way flu is traditionally transmitted through respiratory,” said Monto. “But we are not sure because there are some cattle that have had respiratory symptoms.”
USDA recommends enhanced biosecurity measures, limiting in-state animal movement and increased testing for livestock to reduce spread of the virus, which has recently been found to exist outside of farm facilities.
In the last couple of months, traces of the virus have begun showing up in wastewater across several Michigan cities including in Jackson and Mount Pleasant according to recent wastewater data.
Even though avian influenza has been identified in wastewater, its presence doesn’t necessarily mean an area is experiencing an outbreak, according to the CDC, because the monitoring methods aren’t yet able to identify what subtype of bird flu is being detected in wastewater.
“Wastewater in Warren is showing positive H5 (avian influenza) and one piece of genetic material from H5N1 (current avian flu outbreak virus),” said Monto. “All this really means is that we’ve got to have more testing and try to get to the bottom of the transmission.”
Currently the state of Michigan is awarding $28,000 dollar grants to twenty dairy farms impacted by bird flu to participate in research related to the recent outbreak.
