The West Nile Virus - Essay Example

The West Nile Virus Introduction West Nile Virus or WNV is a type of flavivirus (Family Flaviviridae), and it comprises of the viral group that belong to the Japanese encephalitis antigenic complex type. WNV is the causative agent for encephalitis, a brain fever that causes inflammation of the brain parts, often leading to death. This virus is transmitted to humans and other animals by the different species of mosquitoes, namely, Anopheles, Aedes and the Culex, and is mainly found in the temperate and tropical regions of the world. Though mosquitoes are seen as the primary transferors of the WNV virus to humans, it is the birds that are said to form “the natural reservoir (amplifying) hosts, and WN virus is maintained in nature in a mosquito-bird mosquito transmission cycle primarily involving Culex sp mosquitoes” (Campbell, Marfin, Lanciotti and Gubler, September 2002). Body A brief history: “The West Nile Virus is native to Africa and has existed there, infecting people and wildlife, for thousands of years. But in the 1990s it travelled beyond the borders of its native land. It arrived in Romania in the summer of 1996 and in America in the summer of 1999” (Margulies, 2003). Though present in the African continent for many years, this virus was first isolated in 1937 from an adult woman in Uganda, in a region known as the West Nile district. Before it reached the temperate regions of America in the 90s, there had been outbreaks in other parts of the world (Israel in the 50s, and Egypt and France had faced equine infections during the early 60s), and the virus was known to cause inflammation of the brain and the spinal cord, a condition known as meningocephalitis. In America the first detected case in 1999 was in the area of New York City, and soon there were reported “59 hospitalised cases and seven deaths” (Campbell, Marfin, Lanciotti and Gubler, 519, September 2002). This infection soon spread to other parts of America and cases were reported from in as many as 46 states including the District of Columbia. Its outbreak continued till 2008 and according to the statistics available at the US Centers for Disease Control and Prevention (CDC), there were 1356 cases reported for the year 2008, with 44 fatalities. However, what is remarkable is that the number of cases have gone down dramatically in 2010, with only 26 reported cases so far and only 1death ( CDC, 20th July 2010). Life cycle of the virus: The virus enters the body of a mosquito while it sucks blood from an infected bird, which may or may not show any outward symptoms of the disease. Once inside the mosquito this virus is easily transmitted as this insect bites other animals and human beings, thus passing on the virus into the blood of its host, through its saliva. There have been no records of any other animals being the carrier of this virus, and studies have revealed that “Mosquitoes have not demonstrated the ability to feed on an infected horse and ingest enough of the virus to transmit it to other animals” (California Department of Food and Agriculture, 2005). The infected birds form the vector and are an important part of the virus lifecycle. Crows and the common brown house sparrows are the most common vectors that form the main bird reservoir, for the transmission of this virus in America. So very often, when a large number of these birds start dying suddenly, it serves as a warning bell to the concerned authorities. So the transmission of the WNV follows this cycle: 1. Birds -----WNV--------2. Mosquitoes----WNV----3. Humans/ other vertebrates However during the outbreak of the disease in USA some very unique modes of transmissions were noticed and reported by CDC, and that included instances of the disease spreading through breast feeding, by organ transplantation and also through blood transfusion. These new modes of transmissions have made it compulsory for the US blood banks, from 2003 onwards, to test their donors for the presence of this virus. Symptoms of the disease: The WNV after infecting a human may manifest itself into a variety of symptoms. In majority of the cases the patients complain of a mild fever with slight headache and body aches, skin rashes, and swelling of the lymph nodes. “Many people infected with the virus do not become ill or show symptoms, and even when they do, symptoms may be limited to a headache, sore throat, backache, or fatigue” (US General Accounting Office, Report to Congressional Requesters, September 2000). Patients showing mild symptoms take round 7-10 days to recover, however the weakness may prolong for some weeks more. Swollen lymph glands may take around a month to be completely cured Those patients exhibiting a more severe form of infection will show high fever, severe body aches, disorientation, and loss of consciousness, ultimately leading to a coma like stage, when occasional convulsions and body tremors are also noticed. Death is however rare in the WNV case, and most of the fatality reports comprise of the elderly population of the country. Those affected with a severe WNV infection generally take a long time to recuperate, and may show some long term side effects like depression, memory loss, insomnia, and muscular fatigue. The onset of this disease is the highest during the summers with the start of the mosquito season, and carries on up to the winter, till the temperatures reach freezing point. Temperate regions in America and other parts of the world have reported WNV cases during the late summer months or during the early autumn. In places where the winter is not extreme and temperatures milder, may see the infection throughout the entire year. The potential risk group for this infection generally comprises of elderly people, who are 50 years or more of age, while children have been seen to be less prone to fall sick with this viral infection. Treatments and vaccination, if any: Till date there are no specific medications available for this infection. Various researches in this line are still going on, with some experiments showing certain positive results. One such research has shown that an antiretroviral drug called AMD3100, proposed for the treatment of HIV patients has shown some success in controlling the ENV infection. There are also ongoing researches into treating this infection by giving immunoglobulin intravenously, or by giving ribavirin. However till date no specific answer to this problem, in the form of an antibiotic or an antidote, has been found. During severe manifestations of the infection, the patients are given intravenous fluids, and medications that control the patient’s inflammation of lymph glands, brain and spinal cord. For brain injuries (that may occur owing to the inflammation of the brain) to recuperate, intensive support therapy is necessary, along with a careful monitoring of the patient. There is no known vaccination for the humans, in regards to this viral infection. However there are two approved vaccines for the treatment of horses infected with WNV. “There are currently two approved WNV vaccine products available for horses. An initial series of at least two vaccinations, followed by periodic ‘booster’ injections is required with each” (California Department of Food and Agriculture, 2005). Precautionary measures: Owing to the fact that there are no specific treatments available for this viral infection, the best possible thing one can do is to avoid being bitten by mosquitoes. Thus, one can safely say that eradication of the mosquitoes is an effective solution to control ENV. To avoid getting bitten by this insect, one should wear long sleeved clothes and trousers that completely cover the arms and legs. On should also apply mosquito repellant creams or lotions that contain 20-30% N, N- diethyl- meta-toluamide or DEET when outside the house. If possible the clothes should also be sprayed with DEET or permethrin in order to repel mosquitoes. It is also preferable to stay indoors during dusk, early evening, or dawn, when mosquitoes tend to bite the most. Besides these, one should take care not to let water stagnate for many days in containers, near the house or in the gardens. Standing water form the best breeding ground for mosquitoes, so one should take care to remove all long standing water, cover all water holding tanks or reservoirs, and change water in pools once every two or three days. One very important sign of circulating WNV are dead birds in an area. “The public can play an important role in monitoring West Nile virus through reporting dead birds to state and local health departments”(Lee, 2003). Without the presence of any proper treatments or vaccines, precaution is the only safeguard people can take to protect themselves from this viral infection. It would indeed be fortunate if the researchers find some specific treatment for this disease, or invent some vaccination process, so that one may eradicate the disease from the country once and for all. Vaccines have worked wonders in many diseases like small pox, anthrax, and poliomyelitis, saving the lives of so many people. Though at present the mortality factor for WNV is showing to be significantly low, with a proper treatment in place consisting of effective vaccination procedures, would ensure that no further lives are lost in the near future. Conclusion The WNV infection caused from a mosquito bite is a new entry in the American history of viral diseases. Though the fatalities rates are not very high this infection may cause some serious and long lasting damages to the brain of the patient. Till date there are no specific and effective medications, treatments or vaccinations available for this disease, making precautionary measures against the mosquitoes the only way to avoid this infection. References California Department of Food and Agriculture. (2005). West Nile Virus, Equine West Nile Virus in California. Animal Health and Food Safety Services Animal Health Branch. Retrieved from http://www.cvma.net/doc.asp?id=2497. Campbell, G., Marfin, A., Lanciotti, R., and Gubler D. (September 2002). West Nile Virus. The Lancet, Infectious Diseases, Volume 2, 1. Retrieved from http://www.idready.org/courses/LancetInfectDis2002v2p519-Campbell.pdf CDC. (20th July 2010). 2010 West Nile Virus Human Infections in the United States. Retrieved from http://www.cdc.gov/ncidod/dvbid/westnile/surv&controlCaseCount10_detailed.htm Lee, M. (2003) .West Nile Virus: Overview and Abstracts. New York: Nova Publishers, xii. Margulies, P. (2003). West Nile Virus. New York: The Rosen Publishing Group, 5. US General Accounting Office. (September 2000). West Nile virus outbreak: lessons for public health preparedness: Report to Congressional Requesters. Washington DC: DIANE Publishing, 5. Read More