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Mosquito-borne disease in the United States

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1 Mosquito-borne disease in the United States
Renée Huth, D.P.T. Ph.D. Student, Walden University PUBH : Environmental Health Instructor: Dr. David Anderson Term 3, Year 1 Welcome to this presentation on improving the awareness of vector borne illness in the United States, in particular diseases transmitted by mosquitos. My name is Renee Huth and I am a Ph.D. student in Public Health at Walden University.

2 Purpose of Presentation
Health Professionals & Health Educators will be able to: Describe how vector borne diseases are transmitted. Name 3 mosquito–related diseases within the United States and resulting symptoms. Describe 3 environmentally mindful practices each of us can do to reduce the risk of exposure, thereby reducing the incidence or impact. Share knowledge gained with 3 others to “Pay it forward”. As an audience of health and education professionals, your take aways from this presentation include: To gain the ability to describe how vector borne diseases are transmitted. Be able to name 3 mosquito–related diseases within the United States and resulting symptoms. Describe 3 environmentally mindful practices each of us can do to reduce the risk of exposure. In addition, I would like to share with you my personal belief in the concept of sharing knowledge gained by encouraging others to “Pay it forward”. As active participants in this presentation, I will be challenging each of you to share one point of knowledge you’ve gained from this presentation with three others whether peer or student to get the word out about vector borne illness in the US and how each of us can make a difference in prevention.

3 Overview Arthropod borne (Ar-bo-viruses) insects arachnids mosquitoes
fleas lice biting flies bugs arachnids mites ticks Virginia Department of Health. (2012) Vector-borne disease control. Virginia.gov. Retrieved from First let’s start with a definition of a vector. The Virginia Department of Health in 2011 wrote that a “vector” refers to any “arthropod that transmits a disease through feeding activity spreading the microbe or virus through blood sucking”. Vectors are insects and arachnids. There are many Arthropod borne viruses or Arboviruses. These transmitting hosts are listed here. Our main focus for this presentation is Mosquitoes.

4 So how are vector diseases transmitted
So how are vector diseases transmitted? As you can see from this transmission cycle provided by the CDC in 2008, many ideal conditions need to occur such as appropriate weather and climate and availability of host for the vector to multiply. Humans and horses act like incidental hosts indicating that the virus does not typically multiply within them because conditions are not ideal such as temperature, however birds are ideal vertebrate hosts and breeding grounds for viruses such as the ones we will discuss today. The mosquito bites the infected bird and becomes a carrier to the next host, many of which may be human. Centers for Disease Control and Prevention. (2008). Arboviral zoonosis transmission cycle. Retrieved from

5 Exposure/Risk Being outdoors Occupations Recreation Low income areas
Those who are > 50 or < 2 years of age Handling birds which are infected CDC(2011) reported there is a very low risk from blood transfusions and organ transplants You may not be aware that our own environments may promote the breeding of mosquitos, increasing our risk. Consider occupations i.e. surveyors, road construction crews, landscapers, Parks and Recreation, Field researchers, Law Enforcement Officers; or recreational activities i.e. hikers, camping, hunters, water recreational sports that occur outside. Also, consider those of low income without air conditioning or lacking running water and plumbing in their house. Consider how age and autoimmune diseases effect the immune systems so when bitten by mosquitos the elderly or the young whose immune systems have not developed fully are at increased risk for worse outcomes from an infectious bite. Lastly, now that we know transmission involves the bird species as a host, consider our exposure to infected birds. We will discuss some ways of reducing our risk later in this presentation, but first let’s begin with four of the most prevalent mosquito borne diseases in the US. Centers for Disease Control and Prevention. (2011, April 18). West Nile Virus: What you need to know. Retrieved from

6 Mosquito-transmitted diseases in the U.S.
West Nile (WNV) Eastern equine encephalitis (EEE) LaCrosse encephalitis (LAC) St. Louis encephalitis (SLEV) Although you may be aware of mosquito borne diseases of the world such as Malaria which killed an estimated 655,000 people in 2010, Malaria No More (2011) stated that Malaria was eradicated in the U.S. 60 years ago. Instead, I would like to introduce you to four of the lesser known diseases but are currently four of the more common Mosquito-transmitted diseases in the U.S. They include: West Nile virus, Eastern equine encephalitis, LaCrosse encephalitis and St. Louis encephalitis. Malaria No More. (2011). Retrieved from National Institute of Neurological Disorders and Stroke, National Institute of Health. (2011, February 16). Meningitis and Encephalitis Fact Sheet. USA.gov. Retrieved from

7 West Nile virus (WNV) Neuroinvasive Disease Incidence reported to ArboNET, by state, United States, 2011 (as of January 10, 2012) Let’s first look at the West Nile Virus. The U.S. map provided by the CDC in 2012 demonstrates incidence rates by state for the West Nile virus(WNV) neuroinvasive disease. The map was developed based on surveillance reports released by state and local health departments to the CDC's ArboNET system. This map shows the incidence of human neuroinvasive disease (encephalitis, and/or meningitis, and/or acute flaccid paralysis) by state for 2011 with shading representing the number of cases per 100,000 population. The map shows the highest reported incidence of West Nile virus was in Mississippi, Nebraska, Arizona, California, Nevada, Tennessee and Michigan. The WHO (2012) reported that the WNV was introduced to the U.S. from a virus that was circulating in Israel and Tunisia. The WNV outbreak in USA ( ) highlighted that importation of vector-borne pathogens occurs easily and is a threat to the U.S. Since it’s first diagnosis in the U.S in 1999, the NIH (2011) reported that the West Nile encephalitis (WNE) killed 284 people by Case identification increased to 9,862 reported cases of human West Nile disease in 2003 and 560 deaths were reported between 2003 and 2008 (NIH, 2011). The CDC (2011) reported since 2001 over 30,000 people in the United States have been infected with West Nile Virus. Of those 30,000, 4% died (CDC, 2011). The WHO (2012) reported the risk of infection is more severe for adults over 50 and the immunocompromised. Centers for Disease Control and Prevention. (2012). West Nile Virus. Statistics, surveillance, and control. Retrieved from

8 West Nile Symptoms Emergency Symptoms: high fever, headache, neck stiffness, stupor, disorientation, coma, tremors, convulsions, muscle weakness, vision loss, numbness and paralysis. Monitor symptoms: fever, headache, and body aches, nausea, vomiting, and sometimes swollen lymph glands or a skin rash on the chest, stomach and back. So as health professionals and educators what can we do to limit the health problems that follow exposure to WNV? First realize of those who are infected with WNV, only one in 150 people will develop severe illness. However, this one case in 150 may develop permanent neurological effects, so this is an emergency and people should air on the side of caution when unsure what symptoms mean. The CDC reported 20% of those infected will have milder symptoms and may or may not seek medical assistance. Encouraging those with symptoms to seek early care, is key. The CDC (2008) wrote that as with all Arboviruses, “preliminary diagnosis of WNV is based on the patient's clinical features, places and dates of travel , activities, and epidemiologic history of the location where infection occurred with laboratory verification by serum or cerebrospinal fluid (CSF) to detect virus-specific IgM and neutralizing antibodies.” Although supportive care is provided in both cases including intravenous fluids and pain medications, early treatment is more effective treatment since there is no magic pill to prevent or treat those exposed to the West Nile virus. It is also unknown how exposure will effect an unborn fetus, therefore those pregnant who suspect exposure are encouraged to seek medical care. The FDA estimated that between 1 and 2 million people have been infected with WNV and in 2005 responded to a blood donation risk by approving the first West Nile Virus (WNV) blood test to screen donors of blood, organs, cells and tissues . This test is called the Procleix WNV Assay. The assay detects viral genetic material (ribonucleic acid or RNA). This was a positive step forward because, “excluding the cost of mosquito control efforts by governmental agencies, the cost of WNV related health care alone in the U.S. was estimated at $200 million dollars in 2002” (CDC, 2011). Prevention of transmission and early treatment could reduce these costs. Centers for Disease Control and Prevention. (2011, April 18). West Nile Virus: What you need to know. Retrieved from Centers for Disease Control and Prevention, Division of Vector Borne Diseases. (2008, October 9). West Nile Virus diagnostic testing. Retrieved from

9 Eastern Equine Encephalitis Virus Neuroinvasive Disease Cases Reported by Year, 1964-2010
Next is Eastern equine encephalitis or EEE which infects very few in the US, but of those who are infected, 50 % die as reported by the NIH in This means that the spike in 2005 which had approximately 22 cases, 11 died. From 1964 through 2010, the CDC noted 6 cases were reported annually (range 0-21). Note the spikes and dips on this graph. Moore & CDC (1993) reported that EEE demonstrates a nine year resurgence, therefore the next resurgence is expected in 2018. Moore, C.G., McLean, R.G., Mitchell, C.J., Nasci, R.S., Tsai, T.F., Calisher, C.H., …& Gubler, D.J., Centers for Disease Control and Prevention, Division of Vector-Borne Infectious Diseases (1993). Guidelines for Arbovirus surveillance programs in the United States. Retrieved from

10 Eastern equine encephalitis (EEE)
Infects birds, horses and humans Signs and Symptoms: Mild: fever, general flu-like muscle pains, and headache (adults) Severe: coma and death in severe cases (children under 1 year most at risk) The CDC (2010) reported EEE infection is one of the most severe mosquito-transmitted diseases in the United States with approximately 33% mortality and significant brain damage in most survivors. Horses, birds and humans may be infected with EEE and although a vaccine has been produced for horses, none exists for humans yet. Research has identified the EEE culprit, the virus Culiseta melanura, but funding is scarce especially for rare diseases, so health professionals must stay vigilant. Monitoring viral levels of Cs. Melanura is therefore important to limit EEE transmission. Both monitoring of the density of Cs. Melanura and birds are required to project possible amplification the virus progression and react accordingly to prevent transmission of this deadly infectious disease. National Institute of Neurological Disorders and Stroke, National Institute of Health. (2011, February 16). Meningitis and Encephalitis Fact Sheet. USA.gov. Retrieved from

11 California Serogroup Virus Neuroinvasive Disease Average Annual Incidence by County, 1996-2010
The third Arbovirus causes LaCrosse encephalitis (LAC) and is considered the most common of the California Serogroup Viruses according to the CDC (2011). The CDC (2009) wrote that the “La Crosse virus (LACV) is a California serogroup virus, in the genus Bunyavirus, family Bunyaviridae”. According to the NIH (2011), this virus is found most prevalent in the upper Midwest, southeast, and mid-Atlantic regions of the U.S. and is the cause of the most common form of Arbo induced pediatric encephalitis in the United States. The map (CDC, 2011) demonstrates county reported incidence higher in regions in West Virginia, Virginia, Tennessee, Wisconsin, Illinois, Iowa, Ohio, Indiana, as well as eastern Michigan. Centers for Disease Control and Prevention. (2011, September 9). California Serogroup Virus Neuroinvasive Disease* Average Annual Incidence by County, La Crosse Encephalitis. Retrieved from National Institute of Neurological Disorders and Stroke, National Institute of Health. (2011, February 16). Meningitis and Encephalitis Fact Sheet. USA.gov. Retrieved from

12 LaCrosse encephalitis (LAC)
Most of the 100 cases per year diagnosed in the U.S. are children under 16 years of age. Signs and symptoms (rare): Mild: vomiting, headache, fever, and lethargy Severe: seizure, coma, and permanent neurologic damage In the U.S., there are approximately 100 cases per year of LaCrosse encephalitis (NIH, 2011). Symptoms if they occur will progress usually within 5-10 days after mosquito bite. Those at risk most are under the age of 16 years old and typical mild symptoms include vomiting, headache, fever, lack of energy while severe symptoms including seizures, coma and neurological damage such as paresthesia or weakness. National Institute of Neurological Disorders and Stroke, National Institute of Health. (2011, February 16). Meningitis and Encephalitis Fact Sheet. USA.gov. Retrieved from

13 St. Louis Encephalitis Virus Neuroinvasive Disease Cases Reported by State, 1964-2010
Next is the St. Louis Encephalitis virus. This map provided by the CDC (2011) includes cases of St. Louis Encephalitis virus which caused encephalitis, meningoencephalitis, or meningitis. Note that almost all states have reported cases with a few exceptions in the northeast and South Carolina. Cases appear higher along the Mississippi delta and ocean side. Notice some of the states with higher reported frequencies including in New Jersey, Ohio, Indiana, Illinois, Texas, Louisiana, Mississippi, and Florida. What do these states have in common? (Many are the same states as LaCrosse, Industry, waterways) Centers for Disease Control and Prevention. (2011b, June 13). St. Louis Encephalitis Virus Neuroinvasive Disease Cases Reported by State, Retrieved from

14 St. Louis Encephalitis (SLEV)
The CDC (2011a) reported an average of 102 cases annually (range 2-1,967) between 1964 and 2009. Cases are typically in late summer in temperate weathered areas of the country. Signs and symptoms: 7-10 days Mild: headache and fever (children) Severe: confusion and disorientation, tremors, and coma (elderly) One exception: convulsions (very young) The CDC (2009) reported many vectors transmitted by mosquito cause the St. Louis Encephalitis. They include Cx pipiens and Cx quinquefasciatus in the east, Cx nigripalpus in Florida, and Cx tarsalis and members of the Cx pipiens complex in western states (CDC, 2009). Although 102 cases are reported on average per year, the number fluctuates with periodic spikes of case numbers in the thousands like occurred in the late seventies. This disease appears to be more severe for adults versus children which makes it different than Eastern equine encephalitis and LaCrosse encephalitis which primarily are more severe for children. Centers for Disease Control and Prevention. (2011a, June 13). Saint Louis Encephalitis. Epidemiology & geographic distribution. Retrieved from

15 Environmentally mindful prevention
Personal Environment Community Making a “world” difference Now that you know about some of the more prevalent vector borne diseases in the U.S., let’s discuss some ways we can protect ourselves. The third learning objective of this presentation was that you would be able to describe 3 environmentally mindful practices you can do to reduce the risk of exposure, thereby reducing the incidence or impact. Let’s look at this objective from a personal, a community and a global level.

16 Personal & Ambient environment-limited biting and breeding
Stay indoors (dusk and dawn). When outdoors: Wear long, loose and light-colored clothing. DEET Limit perfumes, scented soaps and lotions-better yet shower after. Travel planning Ambient Environment Clear roof, gutters and downspout screens Do not allow water to collect and stagnate Clean birdbaths, fountains, and wading pools weekly.  Trim grass regularly. One of the ways Moeller (2011) defined our personal environment was that it is “the one over which we have control, in contrast to the ambient or (outdoor) environment (p.4). Each of us can heed the mosquito buzzing warnings and go indoors when mosquitos are out for instance at dusk and dawn, but remember this is not all inclusive prevention technique due to evasive species of mosquitos which are out all day. Also, the Illinois Department of Public Health (n.d.) wrote that dusk and dawn may be the time when your community fogs with ultra-low-volume (ULV) pesticides, so you’ll be protecting yourself from possible exposure of pesticides by staying indoors at these times. We know it is impossible to stay indoors all the time, so when working or playing outdoors in mosquito infested areas, cover up and wear a hat and loose, light colored clothing. Also DEET, according to Turner et al (2011) which works by blocking proteins that insects use to smell their food is good, but make sure to follow directions because some research demonstrates this chemical also may affect our nervous systems. It is also expensive and many mosquitos have become resistant to it now. Consider not showering before working or playing outdoors since many of our shampoos, soaps, deodorants contain attractive perfumes. Also, plan ahead when travelling to areas of the world that might have vector borne diseases you may not be aware of. Other considerations include preventing your home and yard from becoming the breeding ground for mosquitos. Consider ways you can prevent inadvertently breeding mosquitos. Here are a few examples. Illinois Department of Public Health. (n.d.). Prevention & control. Questions and Answers about Spraying for Adult Mosquitoes. Retrieved from Moeller, D.W. (2011). The scope. In Author (Ed.), Environmental Health (4th Ed.), (pp.1-22). Cambridge, MA: Harvard University Press. Turner, S.L., Li, N., Guda, T., Githure, J., Carde, R.T. & Ray, A. (2011). Ultra-prolonged activation of CO2-sensing neurons disorients mosquitoes. Nature, 474,87–91. Retrieved from

17 Community level U.S. Vector Surveillance based on CDC guidelines (1993) examples: Monitoring rainfall and temperature Testing vertebrates (Cs. Melanura for EEE prevention) Community fogging efforts, pesticides Turner et al. (2011) have possibly found a more environmentally friendly option to DEET that activates the mosquitos’ cpA neurons, which is what they use to sense CO2 . In other words, the cpA neurons act like a honing device seeking sources of food. The chemical, 2,3-butanedione (diacetyl) which to us smells like popcorn butter, blocks these neurons in mosquitos leaving them in the dark to where food sources may be. Since this option is still in need of EPA approval, surveillance of breeding grounds is the key to prevention. The Division of Vector-borne Infectious Diseases (DVBID) & the Centers for Disease Control and Prevention (CDC) are the national authorities that oversee U.S. vector surveillance. Local, state and federal agencies are no longer required in to report cases of arboviral encephalitis, but the CDC (1993) reported continued team efforts are invaluable. Surveillance includes monitoring rainfall and temperature patterns in order to predict vector populations in swamps, fields, flood water areas, and coastal salt marshes. In addition, testing birds which are known hosts may help keep an eye on possible fluctuation increases. In addition, you can become familiar with your community’s efforts including fogging and spraying as well as efforts to decrease breeding grounds where waters may be stagnant i.e. local storm water drainage and runoff ponds from roads and business parking lots. Moore, C.G., McLean, R.G., Mitchell, C.J., Nasci, R.S., Tsai, T.F., Calisher, C.H., …& Gubler, D.J., Centers for Disease Control and Prevention, Division of Vector-Borne Infectious Diseases (1993). Guidelines for Arbovirus surveillance programs in the United States. Retrieved from Turner, S.L., Li, N., Guda, T., Githure, J., Carde, R.T. & Ray, A. (2011). Ultra-prolonged activation of CO2-sensing neurons disorients mosquitoes. Nature, 474,87–91. Retrieved from

18 Global Environmental Efforts
As practitioners, stay vigilant to questionable symptoms. Increase natural predators of mosquitos. Reduce pollution to reduce global warming. Consider alternatives to chemicals such as pesticides and household cleaners CO2 emissions-seek alternative fuel sources and ways to limit use of electricity One of the viral infections we have not talked about today is Dengue fever. It is another mosquito borne disease that with global warming is spreading through the Americas with an estimated 50 to 100 million infections, a half-million hospitalizations, and 22,000 deaths each year according to Knowlton et al. in This disease is rapidly adapting to more temperate areas, and has had a 30-fold incidence increase in the last 50 years. Shuman (2011) brings to light that humans have become world travelers, drugs and pesticides have changed resistance to disease, urbanization and climate changes are changing bird migration patterns, and reduced health services following natural disasters all impact vector borne disease proliferation on our globe. We need to begin to seek alternatives and all do our part to limit vector borne diseases. As health practitioners, staying current and vigilant to up and coming diseases that pose a threat to your patients is a priority. Make sure to question your patients who show symptoms about their work activities, what they do for recreation and travel to find out if they have had a possible exposure to mosquito infested areas. We need to support research such as Turner et al.(2011) seeking alternatives to DEET or researchers seeking to reintroduce natural predators such as bats, birds, fish, and the dragonfly or even research that may change the genetics of mosquitos to cause a self destruct mechanism (Trevedi, 2011). Remember that as global changes occur and weather systems change, so does the ecology, for example as wetlands dry up, alternative breeding grounds are found, possibly in your backyard. As community members, seek alternatives to reduce global pollution including ways to reduce the use of chemicals and pesticides in and around your home. This will not only positively impact your family, but also the community by preventing chemicals and pesticides from returning to the land and water sources impacting the ecology that surrounds us all. This will also prevent the possible natural selection and change in genetics of the mosquito breeds. Think of ways you can reduce the use of electricity and prevent CO2 emissions. One simple solution is to use cold water for laundry instead of hot whenever possible and line dry clothes instead of using the dryer. Many websites are available to provide you suggestions you can do today to limit your impact on the environment today. Knowlton, K., Solomon, G., Rotkin-Ellman, M. & the Natural Resources Defense Council. (2009). Mosquito-Borne Dengue Fever threat spreading in the Americas. Fever Pitch. National Resource Council Defense Paper. Retrieved from Shuman, E.K. (2011). Global climate change and infectious diseases. International Journal of occupational and environmental medicine, 2(1), Trevedi, B.P. (2011, October 24). The wipeout gene (Preview). Scientific American. Retrieved from

19 Think global, act local. Challenge
We’ve made it through all but one of the objectives. I now leave you with a challenge to think global, but act local by sharing information from this presentation with three people you know within the next three days and ask them to spread the word each to three others. Let’s spread the knowledge in ways each of us may prevent the spread of vector borne diseases.

20 Additional Resources For more information on Vector Borne Diseases:
Centers for Disease Control and Prevention, Division of Vector Borne Diseases. World Health Organization, Vector Borne Diseases. For more information on what you can do to reduce mosquito population and alternative means to protect yourself: U.S. Environmental Protection Agency. Pesticides and Mosquito control. Florida Department of Health, Bureau of Environmental Public Health Medicine, Division of Environmental Health. Journal of Pesticide Reform. These additional resources provide a quick reference list. You may note that all but the Florida Department of Health and the Journal of Pesticide Reform were used within this presentation and a more specific APA reference list follows, but this provides a quick link for you to access more information quickly. Florida Department of Health, Bureau of Environmental Public Health Medicine, Division of Environmental Health. (n.d.). Mosquito-borne Diseases in Florida. Retrieved from Cox, C. (2005, Fall). Plant based mosquito repellents: Making careful choice. Journal of Pesticide Reform, 25(3). Retrieved from

21 References Centers for Disease Control and Prevention. (2008). Arboviral zoonosis transmission cycle. Retrieved from Centers for Disease Control and Prevention. (2009, October 16). La Crosse Encephalitis. Retrieved from Centers for Disease Control and Prevention. (2011, April 18). West Nile Virus: What you need to know. Retrieved from Centers for Disease Control and Prevention. (2011, June 10). Eastern Equine Encephalitis. Epidemiology & geographic distribution. Retrieved from Centers for Disease Control and Prevention. (2011a, June 13). Saint Louis Encephalitis. Epidemiology & geographic distribution. Retrieved from Centers for Disease Control and Prevention. (2011b, June 13). St. Louis Encephalitis Virus Neuroinvasive Disease Cases Reported by State, Retrieved from Centers for Disease Control and Prevention. (2010, August 16). Eastern Equine Encephalitis.. Retrieved from Centers for Disease Control and Prevention. (2011, September 9). California Serogroup Virus Neuroinvasive Disease* Average Annual Incidence by County, La Crosse Encephalitis. Retrieved from Centers for Disease Control and Prevention. (2012, January 10). West Nile Virus. Statistics, surveillance, and control. Retrieved from

22 References Centers for Disease Control and Prevention, Division of Vector Borne Diseases. (2008, October 9). West Nile Virus diagnostic testing. Retrieved from Cox, C. (2005, Fall). Plant based mosquito repellents: Making careful choice. Journal of Pesticide Reform, 25(3). Retrieved from Illinois Department of Public Health. (n.d.). Prevention & control. Questions and Answers about Spraying for Adult Mosquitoes. Retrieved from Knowlton, K., Solomon, G., Rotkin-Ellman, M. & the Natural Resources Defense Council. (2009). Mosquito-Borne Dengue Fever threat spreading in the Americas. Fever Pitch. National Resource Council Defense Paper. Retrieved from Malaria No More. (2011). Retrieved from Moeller, D.W. (2011). The scope. In Author (Ed.), Environmental Health (4th Ed.), (pp.1-22). Cambridge, MA: Harvard University Press. Moore, C.G., McLean, R.G., Mitchell, C.J., Nasci, R.S., Tsai, T.F., Calisher, C.H., …& Gubler, D.J., Centers for Disease Control and Prevention, Division of Vector-Borne Infectious Diseases (1993). Guidelines for Arbovirus surveillance programs in the United States. Retrieved from National Institute of Neurological Disorders and Stroke, National Institute of Health. (2011, February 16). Meningitis and Encephalitis Fact Sheet. USA.gov. Retrieved from

23 References Shuman, E.K. (2011). Global climate change and infectious diseases. International Journal of occupational and environmental medicine, 2(1), Trevedi, B.P. (2011, October 24). The wipeout gene (Preview). Scientific American. Retrieved from Turner, S.L., Li, N., Guda, T., Githure, J., Carde, R.T. & Ray, A. (2011). Ultra-prolonged activation of CO2-sensing neurons disorients mosquitoes. Nature, 474,87–91. Retrieved from U.S. Food and Drug Administration. (2005, December 1). FDA Approves First Test to Screen for West Nile Virus in Donors of Blood, Organs, Cells and Tissues. FDA News Release. Retrieved from Virginia Department of Health. (2012) Vector-borne disease control. Virginia.gov. Retrieved from World Health Organization (WHO). (2012). West Nile virus. Fact Sheet. Retrieved from


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