Manitoba’s Office of the Chief Medical Officer of Health is updating Manitobans about West Nile virus. At this time, although the weather is warm and mosquitoes are starting to appear, the risk of being bitten by a mosquito carrying West Nile virus is considered extremely low.
Culex tarsalis mosquitoes, the mosquitoes most likely to carry West Nile virus, usually begin to be detected in traps in June, depending on the weather. The majority of the mosquitoes that are out at this time of year are not Culex tarsalis.
Most human exposures to West Nile virus in Manitoba occur in July, August and early September. With warm spring weather, exposure to West Nile virus can occur in June. The possibility of contracting West Nile virus varies from year to year and is based on a number of factors including temperature and precipitation.
The 2007 surveillance and monitoring program for West Nile virus will begin in late May when sampling for Culex tarsalis larvae in standing water begins. Adult mosquito surveillance is scheduled to begin in early June, depending on weather. Human and horse surveillance for West Nile virus is ongoing.
Manitobans can prepare for mosquito season by reducing standing water around their homes. To prevent the development of Culex tarsalis mosquitoes, reducing standing water is most beneficial from June until September. This includes:
· cleaning and emptying eavestroughs, bird baths and other items that might collect water;
· ensuring rain barrels are covered with mosquito screening or are tightly sealed around the downspout; and
· clearing yards of old tires or other debris that collect water.
In 2006, there were 51 human cases of West Nile virus (WNV) identified in Manitoba: 17 cases of the more serious West Nile virus neurological syndrome and 33 cases of West Nile virus non-neurologic syndrome. One case was asymptomatic. There were no reports of deaths associated with West Nile virus in 2006.
Like last year, the West Nile virus dead corvid (birds in the crow family) pickup program will not be in effect in 2007. Dead corvids are no longer tested because they are not needed as an early indicator of West Nile virus in Manitoba. Other indicators, such as mosquito surveillance, are used to estimate the level of human health risk of WNV in the province.
Information on how to safely dispose of a dead bird is available by contacting Health Links–Info Santé at 204-788-8200 or 1-888-315-9257 or by visiting the website at: