The West Nile Virus is a mosquito-borne disease. Although it’s not as dangerous and prevalent as malaria, it’s nonetheless a serious disease. The West Nile Virus isn’t just a disease of humans – it also affects horses, dogs, cats, bats, chipmunks, skunks, squirrels, rabbits, and – most importantly – birds. This means that even in areas where mosquitoes don’t live year round, such as northern climates, a reservoir of the disease still remains and can be transmitted by mosquitoes once they return again with warmer weather.
Mammals, including humans, are considered a “dead end” for the virus. When the virus enters a human or any other mammal, the virus can’t grow enough to be picked up by another mosquito and transmitted to another living being. This isn’t the case, however, with birds, in which the virus continues to multiply to such a level that it can be transmitted to others.
More insidiously, when the West Nile Virus infects humans, there are three different manifestations of the disease. The first manifestation is an asymptomatic infection – in short, you have the disease, but it causes you no problems. The second manifestation is much like having a cold or a very mild case of the flu. In other words, you might have a low grade fever for a few days, but it passes so quickly that most people confuse it with the seasonal flu. You can also develop a mild rash, but all symptoms usually resolve within one week.
The third manifestation is the most dangerous development, marked by neuro-invasive meningitis or encephalitis, and by the development of a near coma state. Fortunately, for every 110 people who will never even know they were infected, there are only 30 people who have the flu-like cold symptom manifestation, and only one person who will experience the life threatening coma manifestation.
In 2007, there were more than 3,600 confirmed cases of West Nile Virus in the United States and 124 people died from the disease. To put this in perspective, there are many more people killed in automobile accidents in only one week than die from the West Nile Virus over the course of one year. The media has considerably stirred the public’s fear of West Nile Virus, even though there are many more diseases that you are likely to be exposed to.
While the mosquito is necessary to transmit the virus, two North American hosts help to amplify the virus. These are the North American Robin and the American Crow, which are the most common carriers of the virus and that serve as reservoirs of the disease. In addition, there are mosquitoes that preferentially bite birds, while others will bite both birds and mammals. No additional mosquito control methods are needed to help prevent West Nile Virus – any method that effectively controls or eliminates mosquitoes will help prevent the transmission of the virus to people.
Fortunately, the West Nile Virus can’t be easily transmitted from human to human – it takes exposure to body fluids to transmit the disease.
So while the West Nile Virus is a disease that’s worth learning about – and though it offers one more reason why mosquito control is important – it certainly isn’t worth the panic the recent media coverage has seemed to incite.