First West Nile positive mosquitoes of the season confirmed in Ottawa, no human cases reported

Ottawa Public Health says routine mosquito trapping and testing have confirmed a West Nile virus positive mosquito pool in Ottawa, the first confirmation of the virus in the city since seasonal monitoring began in June. The bulletin does not say where the trap was located.

A positive mosquito pool is not a human case. OPH says there have been no confirmed or probable human cases of West Nile virus reported in Ottawa this year, and that two human cases had been reported in Ontario as of Sunday, July 26.

Most people who are infected develop no symptoms at all. OPH says about 20 per cent may get flu-like symptoms such as fever, headache, muscle aches and possibly a rash, usually two to fourteen days after being bitten by an infected mosquito. Fewer than one per cent of infections lead to very serious illness in which the virus invades the central nervous system. That risk is higher for people with weakened immune systems and increases with age.

OPH asks residents to apply a Health Canada approved repellent containing DEET or icaridin to exposed skin and clothing, following the manufacturer's instructions, and to take particular care between dusk and dawn when mosquitoes are most active, and at any time in or near shady, bushy or wooded areas. It also advises light-coloured, loose-fitting, tightly woven clothing including long pants, long sleeves, shoes and socks, and window and door screens that fit well and are in good condition.

Around the house, OPH asks residents to remove or regularly refresh anything that holds water for seven days or longer, including bird baths, flowerpot saucers, toys, buckets, cans, old tires, wheelbarrows and swimming pool covers, and to keep all rain barrel openings covered with tightly fitted screen mesh.

Mosquitoes can pose a risk of infection until the first hard frosts of the fall, so OPH says the risk does not end when the weather starts to cool. The agency runs weekly mosquito surveillance and regularly applies larvicide in City-owned roadside storm sewer catch basins, and where necessary at other standing water sites on City property such as ditches and stormwater management ponds.