West Nile virus in Utah
West Nile virus (WNV) is an arbovirus, or arthropod-borne virus, of the flavivirus family. West Nile virus is one of many mosquito-borne viral infections. Several similar types of mosquito-borne viral infections that cause encephalitis, such as St. Louis and Western Equine Encephalitis, have been present in the United States for some time.
In most cases, WNV produces few or no symptoms. However, in some cases, West Nile viral infection may cause more severe symptoms including encephalitis, or swelling of the brain, which can be fatal. Persons over the age of 50 may be at an increased risk of more severe forms of West Nile virus infection.
How is the virus transmitted?
West Nile Virus is primarily transmitted by mosquitoes of the Culex family during normal bloodfeeding. Some species in this family are ornithophilic, i.e. feed primarily on birds, and birds act as reservoirs or amplifying hosts of West Nile virus. Though many species of birds are known to contract WNV, species in the Corvid family (crows, ravens, and jays) are more susceptible to the disease and are therefore useful geographic detectors of West Nile virus.
Mammals, including humans and horses, are considered incidental hosts and are therefore viral 'dead ends.' Humans are most likely to acquire WNV from an infected mosquito, and the virus cannot be transmitted through person-to-person contact. Other mammals, such as horses, do not maintain a high enough level of the virus in the blood stream to transmit the virus to humans.
How can I protect myself and my family from WNV infection?
Prevention is still the best method of avoiding West Nile virus infection. West Nile virus is primarily spread by the bite of an infected mosquito. Protect yourself and your family against mosquito bites. It is important to follow these recommended guidelines:
- Use mosquito repellents with DEET (30 or 35 percent concentration for adults and less than 10 percent for children) or Picaridin, especially from dusk to dawn. Mosquitoes that carry West Nile virus are most active during this time.
- Make sure window screens and screened door are in good repair. Small holes will allow mosquitoes to enter.
- Change water regularly (every two or three days) in birdbaths, outdoor pet dishes, etc.
- Aerate ornamental ponds or contact your local mosquito abatement district regarding treatment options.
- Use mosquito repellent according to label instructions.
- Make sure window screens and screened doors are in good repair. Small holes will allow mosquitoes to enter.
- Eliminate standing water around your home in locations such as old tires, cans, poorly kept swimming pools, or any other source where stagnant water accumulates.
For more information on protecting yourself and reducing mosquitoes around your home, visit epi.utah.gov/west-nile-virus/.
What is the role of the Division of Wildlife Resources?
In the past, the DWR assisted the Utah Department of Health with collecting dead birds as part of a national West Nile virus early detection program. Now that the virus is well-established in the United States, detection is no longer needed as a surveillance tool.
What do I do if I find a dead bird?
Finding one dead bird is not a cause for concern, and a cluster of sick or dead birds is not an indication of WNV infection. It might, however, indicate the presence of other wildlife diseases of concern. Since West Nile virus is now established in the United States, the DWR no longer collects dead birds for WNV testing.
If you notice several dead birds in a small area, these birds might have picked up parasites or bacteria from a local bird feeder. If you have a bird feeder, please clean your feeder once a month using a 10 percent bleach solution for at least ten minutes, and rinse thoroughly. If large numbers of dead birds suddenly appear in a small area, these birds might have been poisoned. Please contact your regional DWR office to report this.
If you find a dead bird in your yard use standard levels of precaution when handling it. Do not pick up a dead bird with your bare hands. Birds die from a variety of causes, and it is important to be cautious. If possible, wear rubber or latex gloves. If gloves are not available, invert a plastic bag over your hand, pick up the bird and un-invert the bag. Seal the bag with the bird inside, then place inside a second plastic bag. Seal the second plastic bag. If available, Ziploc-type bags work well.
Additional information
Follow-up studies
Local links
National links
Answers to frequently asked questions
Question: Is West Nile virus in Utah?
- Answer: Yes, West Nile virus has been found in several Utah counties. Learn more about West Nile virus.
Question: Is there a vaccine available for humans?
- Answer: No, there is currently no vaccine approved for use in humans. The best method of protection is to avoid contact with infected mosquitoes.
Question: How can I protect my horses from West Nile virus infection?
- Answer: There is a vaccine available for use in horses. Please contact your local veterinarian.
Question: What are the symptoms of West Nile virus?
- Answer: In humans, West Nile virus infection typically produces few to no symptoms. In many cases, people infected with WNV have reported feeling flu-like symptoms (i.e. headache, muscle aches and neck stiffness). In rare cases, WNV infection may cause more severe symptoms, such as encephalitis (or swelling of the brain). People over the age of 50 may be at an increased risk of more severe forms of WNV infection. For more information on the symptoms of West Nile virus infection visit the Utah Department of Health & Human Services.
Question: Are my pets at risk of contracting WNV?
- Answer: Very few domesticated cats or dogs have been reported as being positive for WNV. Domestic cats and dogs are considered to be at very low risk of infection.
Question: Should hunters be concerned about eating the game birds they catch?
- Answer: Some gamebirds have tested positive for WNV. However, there is no evidence of human infection by consumption of properly cooked infected game. Hunters are likely at higher risk of infection by mosquito exposure, particularly in wetland environments. Protective measures should be taken to prevent mosquito exposure while hunting. Also, WNV transmission to humans has been documented to occur by accidental injury in the laboratory and by blood transfusion. It is recommended that hunters wear gloves when dressing (cleaning) the birds to protect against accidental injury and exposure to blood. Immediately consult with a physician should an injury occur to discuss the risk of WNV exposure from the injury. Other protective measures recommended to hunters are those that prevent exposure to any infectious organisms carried by game species, including washing hands with soap and water after handling carcasses and cooking the meat thoroughly.
Question: I have a bird feeder and/or a birdbath on my property. Am I at increased risk of catching WNV?
- Answer: At this time, there isn't evidence to indicate that humans can get infected directly from an infected bird. However, we recommended to always follow general hygienic procedures. Birdbaths and feeders should be washed or disinfected regularly (how to clean a bird feeder). Wash your hands with soap and water after touching the baths/feeders. To prevent mosquitoes from breeding on your property, empty and clean birdbaths at least once a week and eliminate any other standing water in your area. Contact local health officials if you are concerned about potential mosquito breeding sites in your area.
Chronic wasting disease
Update:
Here are the CWD sampling areas for the 2024–25 hunting season:
- Book Cliffs
- Boulder/Kaiparowits
- Cache
- East Canyon
- Fishlake
- La Sal
- Manti/San Rafael
- Monroe
- Mt. Dutton
- Nebo
- Nine Mile
- Ogden
- Pine Valley
- San Juan Abajo Mtns
- South Slope (Yellowstone, Vernal/Bonanza, Diamond Mtn)
- Thousand Lakes
Download a PDF of the sampling areas map here. Also view the distribution of CWD cases in Utah.
Visit a check station to test your harvested deer or elk for chronic wasting disease.
Check CWD test results
Chronic Wasting Disease (CWD) is a relatively rare transmissible disease that affects the nervous systems of deer, elk and moose. Infected animals develop brain lesions, become emaciated, appear listless and have droopy ears, may salivate excessively and eventually die. There is no evidence that CWD naturally infects domestic livestock. Chronic Wasting Disease has been detected in free-ranging and captive cervids in multiple states and Canadian provinces (view a map). Recently, CWD was also detected in free-ranging reindeer and moose in Scandinavia.
Where is it in Utah?
Chronic Wasting Disease has been found in three different geographic areas within Utah (view a map). The disease was first discovered in Utah in 2002 in a buck taken during the rifle hunt near Vernal. A second positive was discovered in Utah in early 2003, when a mule deer doe that died in an agricultural field near Moab, Utah, also tested positive. Chronic wasting disease was detected in a third in late 2003 when a mule deer doe taken in a depredation situation near Fountain Green tested positive. As of Sept. 20, 2024, 262 mule deer and six elk have tested positive for CWD in Utah.
What causes it?
Chronic wasting disease is caused by small proteinaceous infectious particles called prions. Prion-caused diseases are known as transmissible spongiform encephalopathies (TSE) and include Bovine Spongiform Encephalopathy (BSE or "Mad Cow Disease" in cattle), Scrapie (in sheep and goats) and Creutzfeldt-Jakob Disease (CJD, in humans). Infected animals may shed prions in urine, feces and saliva. Transmission may occur directly through contact with an infected animal or indirectly through environmental contamination. Prions are extremely resistant in the environment and can stay infectious for years. According to the Centers for Disease Control (CDC), the risk of transmission from animals to humans is considered extremely low.
To date, there has never been any direct evidence that CWD can be transmitted from animals to humans. Recently, preliminary results from a laboratory research project funded by the Alberta Prion Research Institute and Alberta Livestock Meat Agency, and led by a Canadian Food Inspection Agency scientist indicated that CWD has been transmitted to cynomolgus macaques through intracranial and oral routes of exposure. Both infected brain and muscle tissues were found to transmit disease to the macaques.
The CDC recommends not consuming meat from CWD infected animals. Read more information from the CDC about CWD.
Precautions
Hunters should not harvest animals that appear sick, nor should they eat meat from suspect animals. The DWR advises hunters to take these simple precautions when handling the carcass of any deer or elk:
- Do not handle or consume wild game animals that appear sick. Instead, contact your local DWR office and notify them of the location of the sick animal.
- Do not consume meat from animals known to be infected with CWD.
- Wear rubber or latex gloves when field dressing big game.
- On all deer, bone out the meat, and avoid consuming the brain, spinal cord, eyes, spleen and lymph nodes of harvested animals.
- Minimize handling of soft tissues and fluids. Wash hands with soap and warm water after handling any parts of the carcass.
- Knives, saws and cutting table surfaces should be disinfected using a solution of 50 percent household bleach for at least an hour.
- Please contact the Utah Division of Wildlife Resources for additional information or if you see a sick animal while hunting.
Animal afflicted with chronic wasting disease
Photo courtesy of Wyoming Game & Fish
Animal afflicted with chronic wasting disease.
Photo courtesy of Wyoming Game & Fish
What is DWR currently doing about CWD?
The DWR has a monitoring and management plan for CWD that shares factual information with the public, provides early detection, and prevents or minimizes the spread of the disease.
Prior to 2020, units where CWD was previously detected were sampled on an annual basis to monitor the prevalence and distribution of the disease. Units where CWD had not been detected in the past were sampled on a rotational basis in order to detect potential new areas of infection as early as possible.
As of 2020, all units will be sampled on a 5-year rotation, including CWD-positive units. The objective of this type of targeted surveillance is to sample an adequate number of deer that will allow the detection of even a small occurrence of CWD with a high degree of confidence. The removal of symptomatic animals continues on all wildlife management units throughout the state annually. Hunters can help with CWD surveillance efforts by stopping at hunter check stations and allowing the DWR to sample their deer.
Sampling methods
The medial retropharyngeal lymph nodes of mule deer in all sample units, as well as elk from positive deer units, are collected. All samples are sent to the Utah State University Veterinary Diagnostic Laboratory (UVDL) in Logan, Utah, for analysis. UVDL has been approved by the National Veterinary Sciences Laboratory (NVSL) to test for chronic wasting disease. UVDL uses the IDEXX HerdChek CWD Antigen EIA (IDEXX Laboratories, Inc., Westbrook, ME) and the PRECESS 48 system, (Bio-Rad Laboratories, Inc., Life Science Group, Hercules, CA) as rapid tests. Any positives that are detected by the Bio-Rad or IDEXX systems are verified using the "gold standard" Immunohistochemistry (IHC) assay test.
Carcass regulations
The DWR has taken measures to prohibit the import of deer, elk and moose carcasses from known infection areas. Only the following parts of wild deer, elk and moose may be imported from designated infection areas from other states.
- Meat that is cut and wrapped either commercially or privately
- Quarters or other portion of meat with no part of the spinal column or head attached
- Meat that is boned out
- Hides with no heads attached
- Skulls and skull plates with antlers attached that have been cleaned of all brain matter and spinal column matter
- Antlers with no meat or tissue attached
- Upper canine teeth known as buglers, whistlers or ivories
- Finished taxidermy heads
It is unlawful to import dead mule deer, white-tailed deer, elk, moose, caribou, reindeer, or their parts, except for the carcass parts listed above, from states or provinces where CWD has been detected:
- Alberta
- Arkansas
- Colorado
- Illinois
- Iowa
- Kansas
- Maryland
- Michigan
- Minnesota
- Mississippi
- Missouri
- Montana
- Nebraska
- New Mexico
- New York
- North Dakota
- Ohio
- Oklahoma
- Pennsylvania
- Quebec
- Saskatchewan
- South Dakota
- Tennessee
- Texas
- Virginia
- West Virginia
- Wisconsin
- Wyoming
Non-residents transporting harvested deer, elk, or moose carcasses through Utah may do so if they do not stay in Utah more than 24 hours, do not leave any part of the animal carcass in Utah, and do not have their deer, elk, or moose processed in Utah.
How can hunters help?
Immediately report all deer that appear sick or emaciated to a DWR office, biologist or officer. The DWR will attempt to locate the animal and remove a tissue sample from the head for testing.
Hunters harvesting animals from areas where testing is needed may be requested to cooperate by removing the cape from the deer or elk in the field or by taking the head to a Division office immediately after it is caped. The DWR can then remove a lymph node sample for testing.
Can hunters have their deer or elk tested for CWD?
The DWR has implemented an aggressive surveillance plan to target deer in specific units throughout the state. CWD infection in the endemic areas of Wyoming, Colorado and Nebraska are found in less than one percent of wild elk populations and one to 15 percent of wild deer populations. Therefore, testing strategies mainly target deer and not elk, although the DWR will test any deer or elk exhibiting clinical symptoms of CWD. Hunters who have harvested a deer in one of the CWD sampling units, or who harvest an elk in a CWD-positive area, are requested to take their animal to the DWR's Salt Lake, Ogden, Vernal or Cedar City offices (appointment required) or to a wildlife check station to have a tissue sample removed for testing. To qualify for testing, the animal must be older than one year old and the lymph nodes must be intact without having rotted. Hunters may view the results on the Internet after allowing six to eight weeks for processing.
Hunters who harvest an animal in a non-target sampling unit, but still wish to have their deer or elk tested for chronic wasting disease, may do so at a cost by providing the head to the Utah Veterinary Diagnostic Lab in Logan, Utah or the Utah Veterinary Diagnostic Lab in Spanish Fork, Utah. In this case, the DWR will remove a sample from any harvested deer or elk, but the hunter is responsible for getting the sample to the lab and for paying the $25 testing fee. Deer and elk must be older than one year of age to be eligible for testing.
More information
CWD test results
- Hunters: check your results
- Statewide results summaries (PDFs):
2002–03,
2003–04,
2004–05,
2005–06,
2006–07,
2007–08,
2008–09,
2009–10,
2010–11,
2011–12,
2012–13,
2014–15,
2015–16,
2016–17,
2018–19,
2019–20,
2020–21,
2021–22
Maps
Tested sample distribution
CWD sampling unit maps
- 2002–03, 2003–04, 2004–05, 2005–06, 2006–07, 2007–08, 2008–09, 2009–10, 2010–11, 2011–12, 2013–14, 2014–15, 2015–16, 2019–20, 2020–21, 2021–22, 2022–23, 2023–24
Regulations by state
2007 special report
Important links
Want to learn more? Listen to the DWR "Wild" podcast!
DWR Wildlife Veterinarian Ginger Stout takes a deep dive on chronic wasting disease: what it is, how it's spread, where it is currently found in Utah and how hunters can help decrease its impacts to deer populations in the state.
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