MONTREAL - The West Nile virus has reappeared in Quebec as four human infections have been confirmed and a fifth being investigated.

The virus is carried by mosquitoes and the confirmed cases include two in Laval, one in Montreal and one in the Outaouais.

Birds have also been infected, as recent rains have increased the mosquito population, so experts are expecting many more cases to emerge.

In most cases the infection does not cause much harm but the population is asked to take precautions to avoid mosquito bites, particularly those over 50 years old, or anybody whose immune systems is considered vulnerable.

Mosquito nets, bug spray with a DEET or lemon eucalyptus base are all recommended, as is citronella. However those are considered short-term solutions and people are advised to light coloured long sleeved shirts and long pants, and remember that mosquitoes are more active after nightfall.

Residents should also drain any pools of still water where the mosquitoes can breed.