THE WEST NILE VIRUS

West Nile Virus (WNV) is commonly found in Africa, eastern Europe, West and Central Asia, and the MIddle East. it first appeared in North America with an outbreak in the New York City metropolitan area in late summer 1999. It is not known how WNV was introduced to the United States. In succeeding years WNV moved to the west and south and eventually reached Ohio in 2001, causing the deaths of several hundred birds. The first human illness in Ohio due to WNV occurred in 2002. WNV can now be found throughout the continental US and in much of Canada. The Centers for Disease Control reported 3,4004 human cases of WNV in the US in 2007, with 98 fatalities.

People get WNV from the bite of a mosquito that is infected with the disease. In Ohio, the northern house mosquito, Culex pipiens, is believed to be the primary vector to humans. Only a small proportion of Culex and other mosquito species are infected with WNV. Mosquitoes become infected after biting infected wild birds that serve as he primary host of the virus. Members of the Corvidae bird family, especially crows and blue jays, are very susceptible to WNV and frequently die from the disease. Many other kinds of bird may also become sick and die from the disease and scientists are now investigating the role od common backyard birds, such as cardinals and robins, in the disease cycle. Horses may receive a specific vaccination to protect them against possible illness and death. WNV is extremely rare in other animals, such as dogs.

Most people infected with WNV have no symptoms of illness, but some may become ill 3 to 15 days after the bite of an infected mosquito. MIld symptoms of the disease may include a fever, headache, and muscle aches. About 1 out of 150 people develop more severe symptoms, such as high fever, severe headaches, stiff neck, confusion, or muscle weakness, which can result in hospitalization. Most people with sever illness due to WNV are over 50 years old.