Public health officials have advised residents in Toronto to take precautions after a 45-year-old Etobicoke woman tested positive for the West Nile Virus (WNV). The first case of 2006 was officially confirmed last week after the woman spent two weeks in the hospital with the disease.
WNV is a flavivirus (genus Flavivirus) that causes an illness marked by fever, headache, muscle ache, skin rash, and sometimes encephalitis or meningitis that is spread chiefly by mosquitoes. Mosquitoes become infected when they feed on infected birds. Infected mosquitoes can then spread WNV to humans and other animals when they bite.
Experts believe WNV is established as a seasonal epidemic in North America that flares up in the summer and continues into the fall. In 2005, Toronto's first case of the disease appeared in July 30, and totally 38 Torontonians were diagnosed with the disease and six died. This year 26 mosquito pools and eight birds have tested positive for the virus in Toronto. It is typical for human cases to emerge in July and August.
People typically develop symptoms between 3 and 14 days after the infected mosquito bites them. Approximately 80 percent of people (about 4 out of 5) who are infected with WNV will not show any symptoms at all while up to 20% of the people have milder symptoms.
About one in 150 people infected with WNV will develop severe illness. The severe symptoms can include high fever, headache, neck stiffness, stupor, disorientation, coma, tremors, convulsions, muscle weakness, vision loss, numbness and paralysis. These symptoms may last several weeks, and neurological effects may be permanent.
There is no specific treatment for WNV infection. However, in more severe cases, people usually need to go to the hospital where they can receive supportive treatment including intravenous fluids, help with breathing and nursing care.
The easiest and best way to avoid WNV is to prevent mosquito bites. Using insect repellents, wearing long sleeves and pants when the mosquitoes are most active (i.e. dawn and dusk), having good screens on your windows and doors to keep mosquitoes out, and getting rid of mosquito breeding sites by emptying standing water can all help in the prevention of the disease.