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First human West Nile virus case in BC confirmed

VICTORIA – British Columbia has confirmed its first indigenous human case of West Nile virus infection, and laboratory tests are underway to determine if another person has been infected as well.

“The confirmed case is a Kelowna resident and the suspected second case lives in the same household. Both people had travelled within the central and south Okanagan areas and reported being bitten by mosquitoes,” said Dr. Paul Hasselback, medical health officer with the Interior Health Authority. “Last week, a mosquito pool sample collected from the south Okanagan tested positive for West Nile virus, and this week two more mosquito pool samples from the South Okanagan have tested positive.”

“The lab test results we’ve obtained on the first person are sufficient to confirm West Nile virus,” said Dr. Muhammad Morshed, program head, Zoonotic Diseases and Emerging Pathogens, at the Provincial Health Services Authority Public Health Microbiology and Reference Laboratory at BCCDC. “We are still testing blood drawn from the second individual. Given the context, including mosquito positives from the area, we fully expect this case will be confirmed as well.”

All previously recorded cases of West Nile virus in B.C. have been travel-related, acquired outside the province. B.C. has been anticipating the arrival of West Nile virus for several years, given its spread across Canada and the United States.

“Once again, we would like to reiterate that people can and should take common-sense precautions to protect themselves from mosquito bites in the next few weeks, especially when outdoors,” said Dr. Bonnie Henry, medical director of the Vector-borne Disease Program at BCCDC, an agency of the Provincial Health Services Authority. “This includes wearing light-coloured, long-sleeved shirts and long pants – especially in the evenings and early mornings when mosquitoes are most active – and using mosquito repellents that are federally registered, such as those that contain DEET and lemon eucalyptus oil.”

Protective Measures:

There are many simple things you can do to protect yourself from West Nile virus. Unlike birds or other insects, most mosquitoes do not fly very far and tend to stay close to their breeding sites. You are most likely to be bitten by a mosquito from your own backyard.

  • Clean up areas where mosquitoes like to breed. It doesn’t take much time (generally one week) or water for mosquitoes to develop from eggs into adults.
  • Take a look around your home and get rid of mosquito-friendly places that would make good breeding sites or resting places for mosquitoes.
    • Remove any type of standing water at least once a week.
    • Clean up and empty containers that collect water such as old tires, flower pots, wheelbarrows, barrels, tin cans or even small containers like bottle tops that are outdoors.
    • Drill holes in the bottom of used containers so water can’t collect.
    • Change water in bird baths at least once a week.
    • If you have a swimming pool, immediately remove water that collects on pool covers and make sure the pool’s pump is circulating.
    • Turn over wading pools when not in use.
  • Check leaves and drains: Don’t let things pile up.
    • Clear leaves and twigs from eaves troughs, storm and roof gutters throughout the summer.
    • Check flat roofs frequently for standing water.
    • Make sure drains and drainage ditches are not clogged.
  • Stop mosquitoes from entering your home
    • Check windows and door screens for holes and make sure they fit snugly into the frames, so mosquitoes cannot get in.

How can I protect myself and my family when we are outdoors?

  • If you can, avoid being out around dusk and dawn as mosquitoes that carry West Nile virus tend to be active at these times.
  • Wear protective clothing, especially outside in the early evening and at dawn. This includes long-sleeved shirts or jackets, and long pants that mosquitoes cannot bite through. Tuck your pants into socks for extra protection.
  • Avoid dark-coloured clothing, as it can attract mosquitoes.
  • Use mosquito netting for babies and toddlers in cribs and strollers.
  • Use mosquito repellent. Putting on personal insect repellents that are federally registered, such as those that contain DEET, is an effective way to protect yourself from mosquito bites.
  • There are also many repellents that have been shown NOT to protect against mosquito bites, including bug zappers, devices that give off sound waves and Citrosa plants.

  • Tips when using insect repellent:
    • Apply repellent sparingly on exposed skin or on top of clothing. Do not use under clothing.
    • The repellent does not need to be applied heavily to work – a light coating will do.
    • Use your hands to rub the repellent over your skin after you spray it on. Research shows that mosquitoes will find and bite even very small sections of skin missed by the spray.
    • Do not use repellent on open wounds, or if skin is irritated or sunburned.
    • Do not get repellent in your eyes – if this happens, rinse with water right away.
    • Avoid breathing mist from spray-type repellent. Always apply in a well-ventilated area; never apply spray repellent inside a tent.
    • Do not use near food.
    • Read the manufacturer’s instructions on the label carefully, including restrictions for use on young children and maximum number of applications per day.

West Nile Virus Background:

  • West Nile virus is a mosquito borne illness that was first identified in the West Nile Valley region of Uganda in 1937. The first cases in North America appeared in New York in 1999.
  • The usual way for humans to get West Nile virus is through the bite of an infected mosquito.
  • West Nile virus affects a range of animals, including horses. Horse owners in BC are encouraged to talk to their veterinarians about the vaccine that is available to protect their animals.
  • Of people who are infected with West Nile virus, most will have no symptoms at all. About 20 per cent will develop an illness with fever, headaches and rash symptoms. In about 1 out of 150 cases, more severe neurological complications can occur such as encephalitis (inflammation of the brain) and meningitis (infection of the lining of the brain).

Resources:

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Last Updated: November 5, 2009