Etiology and Pathophyisiology: the How

Let's talk about what West Nile does once it is in your body. So we know its coming from a "vector", or a mosquito in this case. This mosquito is carrying the virus and once it bites you this virus goes from it, to you. The mosquito acquired the disease by feeding on the blood of a bird, making it a temporary transport vessel until it gets to another bird, animal, or human. Now lets dispel a myth that you can transfer the disease to others by shaking hands or kissing. This is FALSE, and can not occur.

So, back to you being bitten.......



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Now the virus is in your body, lets discuss what happens and the effects and consequences of this transfer. Once bitten, the virus usually replicates at the site of injection from the mosquito's mouth parts. Here, after sufficient replication of the virus it will travel via the blood stream and lymph system until it reaches its intended location.

The virus passes gate like receptors that are mediated by tumor factor alpha, until the brain and spinal cord are reached. Here, the virus directly invades and infects neurons, especially those that are deep to the grey matter. The infection of these neurons, and those surrounding those that are now impaired, are what contribute to the signs and symptoms of the disease. The paralysis, encephalopathy, seizures, headaches, and other neural disturbances are a direct output of infected and disabled neurons. It is at this point that a healthy immune system will eventually recover and shake off this viral infection. It will take a little time, and it won't be comfortable, but there is a very high survival rate. Now onto those who are more at risk........

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As for lending factors that increase morbidity or mortality, it is mainly age and health status. Through pre-mentioned studies, those over the age of 50 are at a greater risk for serious infection, and then a greater risk of a fatal infection. Those with weakened immune systems, incapable of fighting of a viral disease load are also at risk, despite their age. This includes recent organ transplant recipients who are on medications to weaken the immune system. Other than these two factors, time of year, physical location, and amount of time spent outside (all related to mosquito bites) are directly correlated to getting the infection.

References:
Samuel, M., & Diamond, M. (2006, October 1). Pathogenesis of West Nile Virus Infection: A Balance between Virulence, Innate and Adaptive Immunity, and Viral Evasion. Retrieved April 12, 2015, from http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1617273/

Virology, Pathology, and Clinical Manifestations of West Nile Virus Disease - Volume 11, Number 8-August 2005 - Emerging Infectious Disease journal - CDC. (n.d.). Retrieved April 12, 2015, from http://wwwnc.cdc.gov/eid/article/11/8/05-0289b_article