West Nile Virus (WNV)

Image of micrograph of west nile virus bacteria

What Is West Nile Virus?

In the United States, the West Nile virus (WNV) is the most common mosquito-borne disease. People are most commonly infected after being bitten by an infected mosquito. WNV cases are most common during mosquito season, which begins in the summer and lasts until the fall. No medications or vaccines have proven effective in preventing or treat WNV in humans. Infected people develop a fever and other symptoms in about 1 in 5 cases. One in every 150 people infected develops a serious, sometimes fatal illness. 1Go To Source cdc.gov -“West Nile virus”

Learn More: Wildlife Diseases Spreadable To People

Which Species Is Affected By West Nile Virus?

Birds are the primary hosts of the West Nile virus (WNV), but it can also infect bats, horses, cats, dogs, chipmunks, skunks, squirrels, domestic rabbits, alligators, and humans.

The virus is transmitted through the bite of an infected mosquito (vector). When mosquitoes feed on birds, they become infected. When infected mosquitos bite humans and other animals, they can spread WNV. A person or animal will not always become ill after being bitten by an infected mosquito.

The majority of WNV-infected animals show no signs of illness. Infected horses may experience lethargy, weakness, incoordination, paralysis, or even death due to encephalitis. In birds, death is a possibility, and a small number of dogs have been infected with the virus, but they are generally healthy. 2Go To Source cfsph.iastate.edu -“West Nile Encephalitis West Nile Fever”

How Is West Nile Virus Spread?

Image of mosquito with WNV

The West Nile virus is transmitted to humans and animals through mosquito bites. After infected mosquitos bite birds, the birds become infected and spread the virus.

The majority of West Nile virus infections occur during the summer when mosquitoes are most active. The incubation period, which is the time between being bitten by an infected mosquito and showing signs and symptoms of the illness, is usually four to ten days.

There have also been reports of virus transmission from mother to child during pregnancy or breastfeeding, as well as laboratory exposure to the virus, but these are uncommon. 3Go To Source mayoclinic.org -“West Nile virus”

Can People Or Pets Contract West Nile Virus?

In the same way that infected mosquito bites infect humans, infected mosquito bites infect pets. The virus is kept alive in the salivary glands of the mosquito. The virus is injected into the animal during blood feeding. The virus then multiplies and infects a susceptible animal, causing clinical signs. The majority of infections are undetectable or mild. Consult your veterinarian if your pet exhibits symptoms of fever, depression, incoordination, muscle weakness or spasms, seizures, or paralysis. Your veterinarian will examine your pet and determine the best course of action. 4Go To Source portal.ct.gov -“West Nile Virus In Domestic Animals and Birds”

West Nile Virus Symptoms In Humans

If you’ve contracted the West Nile virus, you’ll notice the first symptoms three to 14 days after being bitten. The severity of West Nile virus symptoms varies. The following are examples of severe symptoms:

  • Paralysis
  • Confusion
  • Muscle Weakness
  • Numbness
  • Convulsions
  • Coma
  • Fever
  • Vision Loss

West Nile Virus Symptoms In Animals

Photo of crow carrying west nile virus

Infected wildlife, like humans, can display a wide range of symptoms, from no symptoms to severe neurologic illness. Weakness, stumbling, trembling, head tremors, inability to fly/walk, and a lack of awareness that allows them to be easily approached and handled are common signs in animals. These symptoms, on the other hand, can be caused by a variety of factors. Laboratory testing of the animal’s tissues is the only way to confirm a West Nile Virus infection. 5Go To Source usgs.gov -“How do I know if an animal is infected with West Nile Virus?”

How Harmful Is West Nile Virus?

Most West Nile virus causes show few or no symptoms. One out of every five people will experience mild flu-like symptoms that will go away without treatment.

West Nile virus poses a more serious problem in one out of every 150 cases. It can lead to a potentially fatal infection of the brain and nervous system. Muscle weakness can be a long-term or permanent side effect of this infection. Some people pass away. If you have West Nile symptoms that don’t go away or get worse, see a doctor right away. 6Go To Source my.clevelandclinic.org -“West Nile Virus”

How To Prevent Contracting West Nile Virus?

The most effective way to prevent the West Nile Virus is avoiding mosquito bites and wild animals. Other options include:

  • Install or repair window and door screens.
  • When going outside, use insect repellents and wear long sleeves.
  • Assist in reducing the number of mosquitoes in your area. Remove standing water from flowerpots, gutters, buckets, pool covers, pet water dishes, discarded tires, and birdbaths, among other places.
  • Inspect your property for dead animals or lingering birds.

What To Do If You Or Your Pet Has West Nile Virus?

Since humans and animals are both prone to West Nile Virus, it’s important to know the disease’s symptoms. If a pet is showing warning signs of the virus or has been in contact with a sick bird, they should be taken to a veterinarian right away. A vet will be able to identify what is affecting your pet and what treatment it needs.

If you believe you have symptoms of WNV, visit a doctor right away. There is no vaccine for this virus, and treatment is more effective the earlier the virus is identified.

Discovering how you or your pet was infected with west nile will help prevent future contractions. A wildlife removal professional can trap birds on your property and have the bird tested for the disease. They can also implement exclusion devices and clean up feces that may be carrying WNV.



  1. “West Nile Virus | West Nile Virus | CDC.” Center For Disease Control And Prevention, CDC, www.cdc.gov/westnile/index.html#:%7E:text=West%20Nile%20virus%20(WNV)%20is,summer%20and%20continues%20through%20fall. Accessed 23 Mar. 2021.
  2. “West Nile Encephalitis West Nile Fever.” The Center For Food Security & Public Health, Iowa State University, www.cfsph.iastate.edu/FastFacts/pdfs/west_nile_fever_F.pdf. Accessed 23 Mar. 2021.
  3. Mayo Clinic. “West Nile Virus – Symptoms and Causes.” Mayo Clinic, Mayo Foundation for Medical Education and Research, 19 Dec. 2020, www.mayoclinic.org/diseases-conditions/west-nile-virus/symptoms-causes/syc-20350320.
  4. “West Nile Virus In Domestic Animals and Birds.” CT.Gov – Connecticut’s Official State Website, State Of Connecticut, portal.ct.gov/DOAG/Regulatory/Regulatory/West-Nile-Virus-In-Domestic-Animals-and-Birds#:%7E:text=Can%20sick%20dogs%20or%20cats,to%2Dperson%20transmission%20of%20WNV. Accessed 23 Mar. 2021.
  5. “How Do I Know If an Animal Is Infected with West Nile Virus?” USGS Science For A Changing World, U.S. Department of the Interior, www.usgs.gov/faqs/how-do-i-know-if-animal-infected-west-nile-virus?qt-news_science_products=0#qt-news_science_products. Accessed 23 Mar. 2021.
  6. “West Nile Virus: Symptoms, Rashes, Treatment, Diagnosis & Prevention.” Cleveland Clinic, Cleveland Clinic, my.clevelandclinic.org/health/diseases/10939-west-nile-virus. Accessed 23 Mar. 2021.