Government of Saskatchewan
Quick Search:
       Saturday, April 19, 2014
Saskatchewan! Healthy people. A healthy province.

What is West Nile Virus?

  • West Nile virus is a disease transmitted to humans by a certain species of mosquitoes, Culex tarsalis.

How is West Nile virus transmitted?

  • West Nile virus is transmitted to humans primarily by being bitten by an infected mosquito. Mosquitoes become infected after they have bitten an infected bird.
  • People, horses and other mammals can become infected and are considered "dead-end hosts". This means that a mosquito cannot bite a human or horse and transmit it to humans or other animals. In addition West Nile virus cannot be spread through direct contact such as touching, kissing, coughing, sneezing or drinking from the same cup. 
  • It is possible that a pregnant woman infected with West Nile virus can transfer the virus to an unborn fetus although this is rare. There is also some evidence that West Nile virus can be transmitted through breast milk.
  • Blood transfusions and organ transplants have been confirmed as sources of human infection, but the risk remains very low. All blood products and organs for transplant are carefully screened for the virus.

What are the symptoms of West Nile virus?

  • Most people who have been infected with West Nile virus experience no symptoms and do not get sick. 
  • Up to 20% of those who become infected will display mild to severe symptoms including fever, headache, body aches, nausea, vomiting and sometimes swollen lymph glands or a skin rash on the chest, stomach and back. 
  • Less than 1% of people infected with West Nile virus will develop a more serious illness called West Nile neurological syndrome, which includes encephalitis, an inflammation of the brain. The symptoms can include high fever, headache, neck stiffness, stupor, disorientation, coma, tremors, convulsions, muscle weakness, vision loss, numbness, paralysis, and even death.

When will symptoms appear if I am infected with West Nile virus?

  • When infection does cause illness, symptoms usually begin 2 to 15 days following a bite from an infected mosquito.

How long will symptoms last if I become ill with West Nile virus?

  • The length and extent of illness will vary widely from person to person and will depend on the severity of symptoms. Symptoms may last from a few days to up to several weeks, while severe neurological effects may continue for a longer period of time.

What should I do if I think I have West Nile virus?

  • Contact your health professional or call the Saskatchewan HealthLine at 811 or However, you do not necessarily need to seek medical attention as milder cases tend to improve on their own. 
  • If you develop symptoms of severe West Nile virus illness (for example, severe headaches, persistent high fever or confusion) seek medical attention immediately.

How can I prevent getting West Nile?

1. By minimizing your exposure to mosquito bites:

  • Use appropriate insect repellent when outdoors. 
  • Cover up. Wear light coloured, loose fitting, long-sleeved tops and long pants when outdoors. 
  • Reduce the amount of time spent outdoors between dusk and dawn when mosquitoes are most active.

2. By reducing mosquito habitats:

Culex mosquitoes lay their eggs on standing water. Even small amounts of water allowed to stand for a week or more may produce adult mosquitoes.

  • Regularly clean and empty containers that can collect water such as bird baths and eaves troughs.
  • Clear yards of old tires and other items that can collect water.
  • Ensure rain barrels are covered with mosquito screen or are tightly sealed around the downspout. 
  • Keep bushes, shrubs and lawns clear of overgrowth and debris.
  • Maintain door and window screens so they fit tightly and are free of holes.

Adult mosquitoes like to rest in long grass and sheltered shady areas. You may reduce your exposure to mosquitoes by regularly maintaining these areas around your home. Steps you can take include:

  • Cutting the grass around your home. 
  • Trimming hedges and trees around doorways and outdoor seating areas (ex: decks, patios, etc.).

What about outdoor recreation and work?

  • People who spend a lot of time outdoors for recreation (ex: camping, golfing) or work (ex: farming, construction) should follow the same self protection measures as anyone else (see How Can I Prevent Getting West Nile Virus?). These precautions are especially important in back country areas where there are large amounts of shallow, standing water.

What repellents are considered appropriate?

  • Consider using federally registered personal insect repellents on exposed skin, such as those containing DEET. A light coating will do. The concentration of DEET should be no greater than 30% for adults and no greater than 10% for children. 
  • DEET-based repellents can also be used on top of clothing. DEET does not have to be applied on unexposed skin that is adequately covered by clothing. 
  • Several DEET-free repellents containing picaridin and oil of lemon eucalyptus are federally registered but provide a shorter period of protection. If you are going outdoors for less than 30 minutes, these are safe, effective alternatives. 
  • Always read the label directions for use.
  • Visit the Health Canada website for more information

How would an infected person be treated for West Nile virus?

  • There is no specific treatment, medication, or cure for West Nile virus. Serious cases are treated with supportive therapies to ease symptoms and prevent secondary infections including hospitalization, intravenous (IV) fluids, airway management, respiratory support and good nursing care. Physical or occupational therapy may be needed to help with possible long-term effects.

Is there a human vaccine available for West Nile Virus?

  • Currently there is no human vaccine available for West Nile virus. There are a number of companies currently working on a vaccine, but they are still in the development phases.

Once a person has been infected with West Nile virus and recovered, are they considered to be immune?

The length of immunity after infection is unknown. Any immunity you may develop may decrease over time or with health conditions that compromise the immune system.

Are there long-term effects of West Nile virus?

  • West Nile virus is a relatively new disease in North America, and the long-term effects are not yet fully understood. Most persons with mild fever recover completely within days to weeks. For the few people who develop the rare neurological form of the disease, recovery may take weeks to years.
  • Age is a significant predictor of recovery as those from the younger age groups are more likely to recover faster and more completely compared to those in the older age groups.

Who is most likely to get sick after being infected with West Nile virus?

  • People with weaker immune systems and those with chronic diseases are at increased risk for serious health effects. This may include people with cancer, diabetes, alcoholism, heart disease, or those undergoing medical treatment that can weaken the immune system, such as chemotherapy. While the risk of serious illness increases with age, anyone exposed to mosquitoes in an area where West Nile virus has been detected is at some degree of risk for infection.

Which pets and livestock are at risk?

  • Horses bitten by infected mosquitoes can become seriously ill and die. Younger domestic birds have also been affected by West Nile virus. 
  • Disease due to West Nile virus has not been reported in cattle. Research has shown that weaning pigs may be susceptible to the virus and cases of infected dogs and cats have been reported. Dogs and cats seldom show any clinical symptoms of the disease although cats may occasionally have a mild fever.

When is the risk of getting West Nile virus the greatest?

  • In Saskatchewan, the risk of getting West Nile virus is greatest in July and August. Mosquito traps across the province are monitored throughout the summer to help provide regular, ongoing information on the risk of West Nile virus.

Who can I contact for more information?

Related Links

Information and tips about protecting your family from West Nile virus.

© 2014 Government of Saskatchewan. All rights reserved.