West Nile virus
West Nile virus (WNV) has been present in Saskatchewan since 2002. As of 2018, there have been 158 neuroinvasive cases and 17 deaths.
Employers must take steps to reduce the risk to outdoor workers. People usually get the disease after being bitten by an infected mosquito. Therefore, all outdoor workers need to take precautions to reduce their chances of being bitten by mosquitoes.
What is the hazard?
WNV is primarily a bird virus that is spread from bird to bird and from birds to humans and other animals mainly by Culex species of mosquitoes. Culex tarsalis, a common summer mosquito in southern Saskatchewan, is the species that most often infects people.
Although WNV can cause severe illness in people of any age and any health status, most people infected with WNV have mild symptoms, or no symptoms at all. People with weaker immune systems, including people over the age of 50, people who have had organ transplants, and people with chronic diseases, are at greater risk for more serious symptoms and health effects. (Less than one percent of those people who had infections in Saskatchewan died. All were over the age of 60.)
For updated information on identified human cases of WNV in Canada, visit https://www.canada.ca/en/public-health/services/diseases/west-nile-virus/surveillance-west-nile-virus.html.
For information on Saskatchewan’s management strategy, visit https:// www.saskatchewan.ca/residents/health/diseases-and-conditions/west-nile-virus.
When is the risk to outdoor workers greatest?
The risk occurs during the mosquito season that starts as early as mid-April and lasts until the first hard frost in late September or October. The risk is greatest when the mosquito species that are the primary WNV-carriers are most prevalent, active and biting. This is generally between mid-July to mid-September. Most infections in people occur in late July and early August.
What are the symptoms of WNV infection?
Many infected people have no symptoms and do not get sick. Others may have only mild symptoms. When infection does cause illness, symptoms will usually appear within two to 15 days. The extent and severity of symptoms vary widely from person to person.
In mild cases, there may be flu-like symptoms, including fever, headache, nausea, vomiting and body aches. Some people may also develop a mild rash on the chest, stomach and back, or swollen lymph glands.
Some individuals have weaker immune systems, and thus are at greater risk of developing more severe health effects, such as inflammations of portions of the brain or spinal cord and some paralysis. These conditions can be fatal in rare cases. Most patients who die are elderly.
In the more severe cases, symptoms could include the rapid onset of severe headache, high fever, stiff neck, nausea, difficulty swallowing, vomiting, drowsiness, confusion, loss of consciousness, lack of coordination, muscle weakness and paralysis. Some people with more severe cases have experienced persistent, chronic effects to their muscles or nervous system.
Workers should seek immediate medical attention if they suspect they have the symptoms of WNV or if their skin is penetrated or punctured while handling birds or tissues that may be infected with WNV. There are tests to indicate if a person has been infected. There is no specific treatment, medication or cure for WNV. Serious cases are treated with supportive therapies to ease symptoms and prevent secondary infections. These cases may require hospital or nursing care. A potential vaccine has shown promise and is being tested further. It is not yet licensed for use.
What can employers do to reduce the risk of outdoor workers being exposed to WNV?
The employer should regularly monitor the incidence of WNV cases in the area. Mosquito and limited bird surveys are being done throughout the province this year. An up-to-date map showing these survey results can be viewed on the Government of Saskatchewan website. You can also refer to the Health Canada map for all human cases identified or confirmed in Canada.
The local health region can also be contacted for information on WNV activity in the area. Employers can reduce the risk of WNV by implementing measures to prevent workers getting mosquito bites, even in the absence of WNV in the area.
Occupational Health and Safety recommends that employers develop a written plan, in consultation with the occupational health committee, worker health and safety representative, or workers, where no committee or representative is required. The plan should address the elements listed in the 2005 amendment to section 85 of the Occupational Health and Safety Regulations, 1996. This regulation requires a written plan for infectious microorganisms where workers are likely to be exposed to them. Once a plan is developed, the employer needs to take steps to ensure it is implemented and that workers are trained on the contents of the plan.
For more information on West Nile virus, see the WorkSafe publication, Protecting Outdoor Workers from West Nile Virus, below:
