Hot weather has extended mosquito season into September, and that means West Nile virus is still a threat, says Montana State University entomologist Greg Johnson.

This year, eleven cases of the virus have been reported in New York City and Westchester County and on Long Island, and one man has recently died.

The first case of a human contracting West Nile virus was confirmed in Washington state. Two Illinois residents have died from West Nile virus, bringing the total number of deaths in the state from the mosquito-spread disease this year to five.

In Toronto, Toronto Public Health has reported the first human case of West Nile virus in August 2006. Toronto Public Health was advised of a 45-year-old female resident of Etobicoke diagnosed with West Nile virus. The woman was hospitalized for two weeks.

So far this year, 26 positive mosquito pools and 8 birds have tested positive for West Nile virus in Toronto.

West Nile virus, primarily a bird disease, is transmitted to humans through mosquito bites. Most infected people never get sick, but up to about 20 percent develop mostly mild flu-like symptoms. Severe symptoms, sometimes including fatal brain inflammation, are rare. Mosquitoes normally stop biting when temperatures fall below 50 degrees during the night.

Todd Damrow, Montana state epidemiologist, said he encourages a variety of preventative measures for people. He recommends repellents, avoiding times and places of heavy mosquito activity and covering exposed skin. "Roll sleeves down instead of up," Damrow said. He advises people to reduce mosquito habitat by emptying water out of pails and old tires, for example, and changing the water in bird baths every day. Some communities set up mosquito control districts and spray for mosquitoes."

Doctors also recommend repellents for humans and vaccinations for horses. Repellents containing 20 to 30 percent DEET is adequate. A safer natural alternative to DEET are citronella and eucalyptus essential oils.