More of the type of mosquitoes that carry the West Nile virus have been spotted in in southern Manitoba, provincial health officials said Wednesday.

The numbers of Culex tarsalis mosquitoes found in traps this week increased in most communities in southern Manitoba, particularly in southwestern Manitoba.

Last week, samples of mosquitoes tested positive for West Nile virus in the towns of Deloraine and Boissevain, both in the province's southwest.

The province is not recommending chemical control of adult mosquito populations, such as the use of malathion, at this time.

Residents are encouraged to take precautions to reduce their risk of mosquito bites, such as using repellent, maintaining window screens, wearing long, loose, light-coloured clothing and avoiding the outdoors between dusk and dawn.

They can also reduce their risk of contracting West Nile by reducing mosquito-breeding habitats — standing water — near their homes.

In previous years, the peak risk period for human exposure to West Nile virus has been the last two weeks of July to the first two to three weeks of August.

No human cases of the virus have been identified in Manitoba this year.

In 2007, 582 human cases of West Nile virus were diagnosed in Manitoba, and four deaths were connected to the illness.

Although most people who are bitten by an infected mosquito do not become ill and for those who do, the symptoms are usually mild, the virus can in some cases cause serious illness and death.