West Nile Virus, Essay Example

So where did this potentially deadly virus originate from and why does it pose such a distinct threat to all of us throughout the world? Petersen and Hayes (2008, p.1308) state that the West Nile Virus (WNV) was first isolated and identified in the year 1937 when an adult woman suffering a dangerously high fever in the West Nile district of Uganda, an East African country was diagnosed. Since then, several different strains of the virus have materialized in several parts of the world, including such diverse regions as southern Asia, the Caribbean Islands, Algeria, Romania, Israel, Canada, and the United States. At least eight different types, or strains, of WNV had been officially identified (Petersen and Hayes, 2008) by the year 2002, however not all of them are known to infect humans. WNV first appeared in North America in 1999, and both humans and horses were reported to be suffering from encephalitis like symptoms (Turell, Sardelis, O’Guinn, & Dohm, 2002). The strain that began spreading throughout in the United States in 1999 is closely related to the strain that was experienced in the Middle East (Turell et al., 2002), and the ensuing infection in the United States is a significant milestone in the evolving history of this virus. Kilpatrick (2011) contended that after ten years of studying the ecology and evolution of the WNV that there are three important conclusions that can be made: “Firstly, the WNV transmission in North America was highest in urbanized and agricultural habitats, in part because the hosts of WNV are abundant in human-modified areas. Second, after its introduction, the virus quickly adapted to infect the local mosquito population more efficiently than the originally introduced strain. Thirdly, the highly focused feeding patterns of the mosquito vectors of WNV result in unexpected host species being important for transmission.”

The unexpected host species that Kilpatrick refers to in his paper are certain species of migratory birds.

The WNV infection is a potentially life threatening illness that is transmitted to humans principally by a mosquito bite, and besides humans, WNV is known to infect both birds and other animals. The Centers for Disease Control and Prevention (the CDC is a US government department organization that creates the expertise, all the relevant information, and tools and processes that people and communities need to protect their health) has reported and documented over thirty thousand human cases of the infection in the United States since 1999 (CDC website, 2012). What is unique to WNV is that it is considered a seasonal epidemic pathogen that arises mainly in the summer and can continue to be transmitted well into the fall.

Millions of birds have perished due to the virus, and this reflects the impact that WNV has had on birds and wildlife as compared to its effect on humans (LaDeau, Kilpatrick, Marra, 2007).

As previously stated, the WNV is transmitted to humans by the bite of an infected mosquito, and specifically by the bite of female mosquitoes of the genus Culex that have fed on infected birds as they feed (Kilpatrick, 2011). However WNV does not spread from person to person. Most people with WNV make a full recovery and some sufferers may not even experience any symptoms at all. However some people who are infected do experience mild signs and symptoms such as nausea, muscle aches, fever, headache, vomiting, and sometimes swollen glands or a rash on certain parts of their body. Typically these symptoms can last anywhere from two to ten days in duration. Some sufferers experience far more serious problems, such as high fever, a stiff neck, confusion, tremors, seizures, muscle weakness, loss of vision, and even persistent numbness. These severe symptoms can last anywhere from a few weeks to several weeks, and in some cases the effects may even lead to permanent muscle weakness or even brain damage which results in fatalities.

According to the Centers for Disease Control and Prevention (Centers for Disease Control and Prevention [CDC], 2012, para. 2) “as of October 23, 2012, forty eight states in the US have reported WNV infections in people, birds, or mosquitoes. A total of 4,725 cases of WNV disease in people, including 219 deaths, have been reported to the CDC. Of these, 2,413 were classified as neuroinvasive disease (such as meningitis or encephalitis) and 2,312 were classified as non-neuroinvasive disease.”

So can WNV be successfully treated, and is there a known cure or vaccine? Currently there is no specific medicine, vaccine or treatment available for WNV (The Journal of the American Medical Association, 2012). Most people fully recover from all effects of the virus with sufficient bed rest and care, and they are able to manage the minor symptoms they experience such as headache, fever, and nausea quite successfully.

There are steps one can take to reduce the risk of infection from WNV, and specifically they involve limiting, or eliminating, any exposure to being bitten by a mosquito that may carry the WNV virus. These measures include the following: limit the time spent outdoors between dusk and dawn when mosquitoes are at their most active. Always wear protective clothing that includes long pants, long sleeve shirts, and socks that do not expose any part of the skin. Ensure mosquito netting is completely covering any infant strollers when outdoors, and always use an insect repellent of suitable strength and quality. Ensure all hot tubs, outdoor saunas, and swimming pools, outdoor saunas, are both clean and properly treated with chlorine so as to prevent any possibility of mosquitoes from breeding. Always remove standing water from pool covers and other places where mosquitoes can breed, ensure any plastic wading pools are drained and are set on their sides when not in use. Never let any containers become filled with standing or stagnant water, and store empty pots or garbage cans indoors (CDC, 2012).

Besides mosquito bite prevention and minimising their breeding grounds, there are other ways with which the spreads of WNV can be minimised. Studies have determined that the virus is considerably more prevalent in warmer, more humid weather conditions as compared to the colder climates of some regions (Work, Hurlbut, Taylor, 2001). As mosquitoes are the principal transmitters of WNV, and certain species of birds, chiefly migratory species that travel periodically every year to new feeding and breeding grounds, these bird species appear to be the major starting or amplifying hosts of WNV. If the migratory birds that are susceptible to WNV infection could be quarantined before they commence their voyage then this could contribute to minimising the spread of the virus (Rappole, Derrickson, Hubalek, 2000). Whilst conservationists would more than likely be outraged by preventing the natural migration of such birds, an argument for a temporary migratory cessation in order to control the virus spreading would hold some weight to the debate.

There are factors that we humans cannot control that can potentially have a serious impact on the rapid increase in the infection rate of WNV. Research has suggested that the virus is more prevalent in warmer and more precipitous climates than the opposite (Rappole et al, 2000). If the weather plays a key role in the abundance of mosquitoes who can carry and transmit WNV, then there is little we can do to alter weather patterns and thus the spread of infection in affected regions. If there is a link between climate and WNV transmission, then the possiblility of recurrent outbreaks could become a distinct reality. Therefore increased self-protection, education, and awareness programs would need to be the focus by government authorities as prevention would obviously be far more effective than managing the symptoms once WNV has been contracted. It is interesting to note that WNV epidemics peaked in many areas the year after it first occurred, with fewer human cases having been observed in subsequent years thereafter. This reduction in the WNV disease has led to reduced research focus and less funding from public health agencies for WNV, and, more recently, less testing for WNV by health care providers. The subsequent reduced transmission of WNV could have been a product of many factors, including a higher immunity in birds or humans, and especially those people who would be most at risk such as people who work outdoors for a living (Petersen & Hayes, 2008), or sports and camping enthusiasts.

The ability of WNV to transform, alter and successfully adapt itself to its environment, along with the continuing occurrence of large urban epidemics, as seen in the United States in recent years, all indicate that WNV is likely to remain a serious threat into the conceivable future. The pure nature of the rapid pattern of WNV epidemics that could affect any United States city coupled with the morbidity and mortality attributable to this disease require a thorough risk analysis and assessment so as to be prepared for early and decisive action by the relevant authorities. This risk assessment exercise must be coordinated with the various knowledgeable science fraternities whom much research knowledge can be garnered from so as to ensure any serious outbreaks of WNV that are encountered can be quickly identified, controlled and treated toward successful closure.

References

Kilpatrick, A.M., (2011). Globalization, Land Use, and the Invasion of West Nile Virus, American Association for the Advancement of Science, DOI: 10.1126/ science.1201010 Science 334, 323.

LaDeau, S.L., Kilpatrick, A.M., Marra, P.P., (2007). West Nile virus emergence and large scale declines of North American bird populations. Nature (447) 710-713.

Petersen, L.R., Hayes, E. B., (2008). West Nile virus in the Americas. Medical Clinics of North America, 92 (6), 1307-22, ix Review.

Rappole, J.H., Derrickson, S.R., Hubalek, Z., (2000). Migratory birds and spread of West Nile virus in the Western Hemisphere. Emerging Infectious Diseases Journal. Jul-Aug; 6(4) 319-28.

Turell, M. J., Sardelis, M. R., O’Guinn, M. L., Dohm, D. J., (2002). In Japanese Encephalitis and West Nile Viruses, book. 267, 241–252.

Work, T.H., Hurlbut, H.S., Taylor, R.M. (2001). Indigenous wild birds of the Nile Delta as potential West Nile virus circulating reservoirs. Am J Trop Med Hyg. 4(5):872–888.

Centers for Disease Control and Prevention. (2012). CDC Mission, Core values and Pledge. Retrieved from http://www.cdc.gov/about/organization/mission.htm.

The Journal of the American Medical Association (2012, October 3). Issue (Vol) 308 (13), 1325–1326. DOI: 10.1001/2012.jama.11930 ISSN: 0098-7484.