Penulis: Health Canada
It is the time of year when the outdoor season in Canada begins, as we finally move away from a long, cold winter, to hours of outdoor fun in backyards, parks, and campgrounds. This time of year also marks the arrival of something far less welcome – mosquitoes and the threat of West Nile (WN virus).
Once regarded as nothing more than a pesky nuisance, mosquitoes now carry the risk of illness, disability and, in rare cases, death. Most people infected with the virus have no symptoms or they have mild, flu-like symptoms. Sometimes though, the virus can cause severe illness, resulting in hospitalization and even death.
Although the risk of serious illness is higher for older people and people with weakened immune systems, anyone can be bitten by an infected mosquito and should take active steps to protect themselves and their communities. It is very important to reduce the risk to you and your family by taking steps to avoid mosquito bites.
Recently, scientists have discovered WN virus can be transmitted in other ways, including blood transfusions and organ/tissue transplants. The risk of getting WN virus this way is considered to be quite low. There is also evidence that pregnant women can pass the virus to their unborn babies and that the virus may be passed through breast milk. In addition, laboratory workers who handle infected specimens can get WN virus through needle punctures or cuts.
There is no evidence to suggest that people can get WN virus by touching or kissing someone who is infected, or from being around a health care worker who has treated an infected person. Nor is there evidence that the virus can pass from infected animals to people, including horses and pets.
Who is at risk?
Anybody can have serious health effects with WN virus infection; however, people with weaker immune systems are considered to be at greater risk for serious health effects.
- Older people.
- People with chronic diseases, such as cancer, diabetes, alcoholism, or heart disease.
- People that require medical treatment that may weaken the immune system, such as chemotherapy.
Although individuals with weaker immune systems are at greater risk, WN virus can cause severe complications for people of any age and any health status. This is why it is so important to reduce the risk of getting bitten by mosquitoes. Anyone exposed to mosquitoes in an area where WN virus has been detected is at some degree of risk for infection.
Reduce your risk!
To avoid being bitten by mosquitoes, you can take action on two fronts:
Minimize your exposure to mosquitoes:
- Mosquitoes can bite at anytime – day or night
- When going outdoors, use insect repellents that contain DEET or other approved ingredients.
- Wear protective clothing such long-sleeved shirts, long pants and a hat. Light coloured clothing is best because mosquitoes tend to be more attracted to dark colours.
- Make sure that door and window screens fit tightly and have no holes that may allow mosquitoes indoors.
Eliminate mosquito breeding sites around your home and cottage:
Mosquitoes lay eggs in standing water and it takes about four days for the eggs to grow into adults that are ready to fly. Even a small amount of water, for example, in a saucer under a flower pot, is enough to act as a breeding ground. As a result, it is important to eliminate as much standing water around your property as possible by:
- Regularly draining standing water from items like pool covers, saucers under flowerpots, recycle bins, garbage cans etc.
- Remove old unused items from around your property including old tires, which have a tendency to collect water.
- Change the water in wading pools, birdbaths, pet bowls and livestock watering tanks twice a week.
- Cover rain barrels with screens.
- Clean out eaves troughs regularly to prevent clogs that can trap water.
- If you have an ornamental pond, consider getting fish that will eat mosquito larvae.
What about pesticides?
Over-the-counter products that are designed to get rid of garden pests are not effective for overall mosquito control. For other pesticides, only workers who are licensed by provincial authorities and are trained in the safe use of pesticides can carry out mosquito control programs. Decisions on whether or not to use pesticides to control the spread of WN virus in your community will be made by local and provincial health authorities. For more information, see the Health Canada information sheet “Using Pesticides to Control Mosquitoes”.
West Nile virus symptoms
What to watch for
Many infected people do not get sick and show only mild symptoms or none at all. 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.
- Body aches
- Mild rash
- Swollen lymph nodes.
For those with weakened immune systems WN virus can develop into encephalitis (swelling of the brain) or meningitis (inflammation of the lining of the brain or spinal cord). These conditions can be fatal.
- Rapid onset of severe headache
- High fever
- Stiff neck
- Nausea or vomiting
- Difficulty swallowing
- Loss of consciousness
- Lack of coordination
- Muscle weakness
Anyone who has a sudden onset of these symptoms should seek immediate medical attention.
During 2002, several other symptoms of WN virus were identified including movement disorders, parkinsonism, poliomyelitis-like syndrome and muscle degeneration. Because WN virus is an emerging disease, the long-term effects are not fully understood. Studies to date show that some people with serious symptoms and health effects recover completely, while others experience prolonged health problems.
These problems can include:
- Physical effects- long-term muscle weakness and paralysis, fatigue and headache
- Cognitive effects-confusion, depression, concentration problems and memory loss
- Functional effects-difficulty making meals, going out, shopping or other tasks.
Scientists do not know why some people recover while others continue to have varying degrees of health problems.
Is there a cure on the horizon?
There is currently no specific treatment, medication or cure for the virus although many of the symptoms can be treated. At this time, there is no licensed vaccine to protect people against WN virus. In the United States, the National Institute of Allergy and Infectious Diseases (NIAID) has supported research to develop a vaccine against WN virus, with human trials to begin this year. Health Canada is monitoring these developments closely.