Virology: West Nile Virus

West Nile virus is a type of virus known as flavivirus. It was from an infected mosquito carrying vector from infected bird and spread it through bite into other host, human and other animals. There is no evidence for transmission from person to person. Although many people are bitten by mosquitoes that carry West Nile virus, most do not know they've been exposed. Few people develop severe disease or even notice any symptoms at all. Most cases of West Nile Virus are mild and go unreported.

According to the statistical data recorded from Centre for Disease control (CDC) in 2002, there are 4156 Americans were infected and 6.73 percent cases ended in death. In 2006, it was noted that the expected number of cases was decreasing as the American population was being more and more exposed to the disease. This is because as the person become adult, they became fully immune to the illness, based on studies done in Egypt and Uganda. However, after a few months the CDC reported that there are also cases in U.S. and it was the highest number of infections happens in the history of West Nile virus. This is because the conditions of the weather on that time, which is hot and warm promotes the breeding of the mosquitoes. In 2006, the total number of West Nile virus cases in the U.S. surpassed the totals of 2004 and 2005. Since 1999, cases of the West Nile virus have been reported in Canada, Mexico, the Caribbean, and Central America.

West Nile virus is distributed in North America is discovered as long term effects of West Nile virus distribution in North America are yet to be determined. After a few decades passing by this virus is assumed to be spread eventually integrated in more of our North American eco-systems and will persist. The extent range is increasing uncertainty at that point of time, regarding to the environmental variables change, like in weather conditions and migration patterns. The risk of infection is dependent on many factors, and cannot be based on geographical regions anymore. The West Nile virus poses a substantial threat to the population, but being aware of its history, how it spreads, and how to reduce risk of infection is a first step towards individual protection.


References
Nicholas K. West Nile Virus; Epidemiology and Ecology in North America. In: Advances of Virus Research Vol 61
Alan DT. Barret (2011).Current status of West Nile vaccine development 2011; University of Texas Medical Branch
Karen Foster (2005).West Nile Fact ; Department of Health and Human Services Centres for Disease Control and Prevention
Shannon L. et al (2007).West Nile emergence and large scale declines of North American Populations.In : NATURE letters