Ontario's top health official is warning people to take precautions against West Nile virus because of a sudden increase in the number of positive mosquitoes.

The number of mosquito pools that have tested positive for the illness is on the rise, the province said in a news release.

So far, 46 mosquito pools have tested positive, a figure that is higher than the year-to-date totals from the last four years.

The lone human case reported in Ontario in 2011 was a travel-related case, health officials said.

Dr. Arlene King, Ontario's chief medical officer of health, said people can protect themselves by:

• Wearing light-coloured clothing, long-sleeved shirts, long pants, socks and shoes while outdoors

• Using insect repellent containing DEET

• Avoiding the outdoors at dusk and dawn when mosquitoes are most active

• Repairing and replacing ripped or broken screens on windows and doors to prevent mosquitoes from entering your home

People can also eliminate prime breeding grounds by draining standing water on their property.

West Nile symptoms

Most people who contract West Nile virus experience mild illness, including fever, headaches, body aches, nausea, vomiting and a rash on the chest, stomach or back.

Serious symptoms include muscle weakness, a stiff neck, confusion, tremors, numbness and sudden sensitivity to light, the province said.

Symptoms usually develop between two and 15 days after being bitten by an infected mosquito, the news release stated.

Lyme disease

Health officials are also warning people about the dangers of tick bites, including Lyme disease, a rare but serious illness.

The risk of getting Lyme disease is low, the province said.

If it isn't treated, it can affect the heart, nervous system and joints.

The province is offering these tips to avoid tick bites:

• Wear light-coloured clothing, long-sleeved shirts, long pants, socks and shoes while outdoors

• Tuck your pants into your socks

• Use insect repellent containing DEET

• Stay on paths and avoid overgrown bush while hiking

People should search their body for ticks at least once a day if they venture into an area where they may be exposed to Lyme disease.

How to remove a tick

If a tick is located on your body, here is how you should remove it:

• Use tweezers

• Grasp the tick as close to the skin as possible and pull it straight out, gently but firmly

• Save the tick in a jar or screw-top bottle and take it to a local public health unit for testing

Since 2008, there have been about 100 Lyme disease cases reported in Ontario each year. Forty-one cases have been reported in 2011.

For more information on Lyme disease, click here.