REGIONAL— Test results are in from the first year of a multi-state study on West Nile virus in ruffed grouse in Minnesota, Michigan and Wisconsin— and they show that while the virus is present in Minnesota and neighboring states, exposed grouse can survive. 
In 273 samples from grouse that hunters harvested in Minnesota during 2018, 34 samples (12.5 percent) had antibodies consistent with West Nile virus exposure. Those results were confirmed in ten of the Minnesota samples, while results suggested likely West Nile exposure in the other 24 samples. The tests did not find the presence of the virus in any of the ruffed grouse hearts, meaning the birds were not sick when harvested.
In Wisconsin, West Nile virus exposure was detected in 29 percent of ruffed grouse blood samples and two grouse had virus present in their hearts. In Michigan, West Nile virus exposure was detected in 13 percent of ruffed grouse blood samples, with four having virus present in their hearts.
“The study tells us that some birds that have been exposed to West Nile virus are surviving – both juvenile and adults – and they are not sick when harvested in the fall,” said Charlotte Roy, grouse project leader with the Minnesota Department of Natural Resources. “But this study does not tell us about birds that may have died from the disease over the summer.”
The DNR had asked grouse hunters to collect two types of samples to help determine if the birds were exposed to the virus: a blood sample to determine if the grouse had developed an immune response to the virus, and the heart to look for traces of viral genetic material. As in humans, ruffed grouse can build up antibodies in an immune response to viruses they encounter. Even when the body fights off an illness, these antibodies are left behind in the blood.
Hunter participation
Hunters who submitted samples in 2018 will be mailed a letter this fall notifying them of the test results of the birds they submitted.
Sample collection is continuing during the 2019 grouse hunting season. Sample collection kits have been available for pickup at DNR area wildlife offices within the ruffed grouse range since Labor Day on a first-come first-served basis. Due to strong interest by hunters, many offices are already out of kits, so hunters should call ahead before stopping. 
About West Nile virus
West Nile virus has been present in Minnesota since the early 2000s, but interest in effects on ruffed grouse increased following a study in Pennsylvania documenting relationships between habitat quality, populations and virus exposure. Some bird species recover quickly and become tolerant to the virus while others, such as blue jays and crows, suffer higher rates of mortality.
West Nile virus is carried by infected mosquitoes. Not all people or animals bitten by an infected mosquito will contract West Nile virus. There have been no documented cases of people contracting West Nile virus from consuming properly cooked meat.