By Anuoluwa Akibu, Jack Griffin, Sierra Petties, & Ben West, III Form; with mentors Ben Robb, V Form & Blaine Duffy, VI Form

The West Nile Virus: The Minor Zoonotic Problem Without A Major Solution

Abstract

In the information below, you will be able to take away a full understanding on the West Nile virus, and how it is transmitted zoonotically. West Nile virus (WNV) is a pathogen, specifically a flavivirus, and it is found in arthropods. West Nile virus infections are most common in temperate areas, between late summer and early fall, when mosquito activity is at it’s peak. Although many people become infected with WNV most people do not show symptoms. The few who do, mostly have minor symptoms like fever and headache. One percent of the people infected with the virus develop lethal symptoms that require immediate medical assistance. Most cases of West Nile virus come from mosquito bites. The mosquitoes infect humans and other animals which are called dead end hosts. Dead-end hosts cannot pass the disease on to another host. Birds however are different because they are amplifier hosts. That means they continue to spread the disease to mosquitoes have not received the virus yet. The only known treatment to West Nile virus at the moment is pain killers because scientists are still figuring out a solution. There are cures for animals and some in development for humans. There isn’t a practical solution to West Nile virus, but there have been prevention methods created. The main focus for many groups worldwide is of the disease by managing the mosquito population and observing the bird population to restrict the further spreading of the disease. Researcher(s): All;  Editor(s): All

Background

West Nile Virus (WNV) is a flavivirus that is a genus to the Flaviviridae family, a family of “positive, single stranded, enveloped RNA viruses” and found in arthropods (“Flaviviridae”). West Nile Virus is also an arbovirus because mosquitoes are the primary vectors of WNV. Mosquitoes become infected with WNV when they take blood from infected birds which are the primary hosts of the virus and there are over 320 species of birds that scientists have identified with WNV. When infected mosquitoes bite humans or animals they transmit the West Nile Virus and this continues through a host-vector-host cycle (“West Nile Virus”). WNV can be transmitted from a human host to an animal host, therefore it is a zoonotic disease. West Nile Virus was first identified in a feverish woman living in the West Nile District of Uganda in 1937 (“West Nile Virus”). Since 1937 outbreaks of WNV have transpired in Africa, Asia, Australia, Western Europe, the Middle East and tropical islands in the Pacific Ocean (“West Nile Virus”).  Then in the United States in August 1999 WNV was first identified, in New York City (“West Nile Virus Slideshow” 2) and it soon spread across the United States except Alaska and Hawaii and into Canada and Mexico (“West Nile Virus”). From 1999 to 2008 the Centers for Disease Control and Prevention (CDC) noted 64 mosquito species that were infected with the virus, Culex pipiens and Culex tarsalison being the most common mosquito carriers of the virus found in the U.S (“West Nile Virus”). Researcher: Anu; Editor: Sierra

Geography

West Nile virus infections are most common in temperate areas, between late summer and early fall, which is when mosquito activity is highest (“West Nile Virus Causes” 12). In regions where the weather is usually mild, WNV infections can occur year round. Medical professionals began studying the zoonotic disease after it was first identified in Africa, in the West Nile District of Uganda. It is believed that WNV infections have occurred throughout Africa and the Middle East before being identified in 1937 (Chancey, Grinev, Volkova and Rios). In 1939-1940, a serosurvey, a test of blood serum from a group of people to find the amount of pathogen that group has, was conducted to determine the seropositivity for WNV in countries of Africa (Chancey, Grinev, Volkova and Rios). They found seropositivity “in Uganda, Sudan, the current Democratic Republic of the Congo, and Kenya…over 50% in some localities” and in South Africa, seropositivity in humans and animals were found in samples collected in 1954 (Chancey, Grinev, Volkova and Rios). This shows that the presence of WNV has circulated largely throughout Africa and the Middle East even before the studies began. WNV is more prevalent in Africa but the virus has spread rapidly across the world. For example, in the U.S. “from 1999–2013, there have been a total of 39,557 reported cases of WNV in the U.S. of which 17,381 were WNND, resulting in 1,667 deaths, an average of 111.1 deaths/year” (Chancey, Grinev, Volkova and Rios) As seen in Figure #1 WNV has already caused an endemic and large neuroinvasive disease outbreaks in the first few years it has been in the U.S (An Epidemic). Ultimately, West Nile virus is most common in Africa and the Middle East, but has spread beyond its relative environment. Researcher: Anu; Editor: Sierra

Figure #1: These are four maps show the progression of WNV neuroinvasive disease cases in the United States from 2001-2004. It started on the east coast, but overtime spread to the midwest and west coast.

Symptoms

In most cases, people with West Nile virus (WNV) have no signs or symptoms (“West Nile Virus”, CDC). Around 80% of people infected will not experience any symptoms but those who do often develop a minor case of WNV called West Nile Fever (“West Nile Virus”, CDC). WNV’s incubation period is typically 2 to 15 days, and symptoms consist of fever, headache, body aches, vomiting, diarrhea, fatigue, and skin rash, see Figure #2 (“West Nile Virus”, Mayo). This form of WNV is referred to as West Nile fever and it is not deadly (“West Nile Virus Infection”). Only one percent of people with WNV are infected with a more virulent strain (“West Nile Virus Infection”). This strain causes inflammation of the brain and membranes around the spinal cord, creating a serious neurological infection (“West Nile Virus Infection”). Symptoms of this more serious case of WNV are high fever, severe headache, stiff neck, disorientation or confusion, stupor or coma, tremors or muscle jerking, seizures, partial paralysis or muscle weakness (“West Nile Virus Infection”). These are referred to as West Nile meningitis and West Nile encephalitis. Symptoms of encephalitis, inflammation of the brain caused when the virus crosses the blood brain barrier, can last for months (West Nile Virus). This barrier is there to prevent such diseases from spreading into the vulnerable part of the brain (“West Nile Virus”, Mayo). If the virus does cross this barrier then the virus can become lethal (“West Nile Virus Infection”). Most people recover from the symptoms of WNV, but if there are signs of serious infection such as severe headaches, a stiff neck, disorientation, or confusion then immediate medical attention is strongly suggested (“West Nile Virus Infection”). Again, WNV virulence is more often than not minor. Of the less than one percent who are severely affected, only about ten percent of them die from the disease (“West Nile Virus Infection”). Researcher: Ben and Jack; Editor: Ben

 Treatment

The West Nile virus (WNV) is not a very serious or fatal virus for the majority of the people infected with it, as stated in the symptoms and how it harms the body section. The small percentage of people who do begin to experience with symptoms of WNV have to live with it until there is a cure because it is a virus. Currently, there is no specific treatment or vaccine for West Nile virus (“CDC West Nile Virus Symptoms and Treatment,” 2015) and according to the world’s current knowledge on viruses there won’t be a cure for West Nile virus for a while. People that do experience symptoms such as aching and vomiting use “over-the-counter pain relievers” (“CDC West Nile Virus Symptoms and Treatment,” 2015) to help with the pain. However, this is for the small amount of people who “develop a fever with other symptoms such as headache, body aches, joint pains, vomiting, diarrhea, or rash” (“CDC West Nile Virus Symptoms and Treatment,” 2015), and there is an even smaller number of people with the virus that experience serious health issues. “Less than 1% of people who are infected” (“CDC West Nile Virus Symptoms and Treatment,” 2015) with the West Nile virus “will develop a serious neurologic illness such as encephalitis or meningitis (inflammation of the brain or surrounding tissues)” (“CDC West Nile Virus Symptoms and Treatment,” 2015). These are very serious infectious, but they do not have cures either. Overall, there is no cure for the West Nile virus, but there is not a large demand for one either.

The West Nile virus (WNV) is not a very serious or fatal virus for the majority of the people infected with it, as stated in the symptoms and how it harms the body section. The small percentage of people who do begin to experience with symptoms of WNV have to live with it until there is a cure because it is a virus. Currently, there is no specific treatment or vaccine for West Nile virus (CDC West Nile Virus) and according to the world’s current knowledge on viruses there won’t be a cure for West Nile virus for a while. People that do experience symptoms such as aching and vomiting use “over-the-counter pain relievers” (What Is West Nile) to help with the pain. However, this is for the small amount of people who “develop a fever with other symptoms such as headache, body aches, joint pains, vomiting, diarrhea, or rash” (CDC West Nile Virus), and there is an even smaller number of people with the virus that experience serious health issues. “Less than 1% of people who are infected” (CDC West Nile Virus) with the West Nile virus “will develop a serious neurologic illness such as encephalitis or meningitis (inflammation of the brain or surrounding tissues)” (CDC West Nile Virus). There isn’t much treatment for WNV, but there are many ways to prevent one from contacting the virus. In Figure #3, there are multiple ways to prevent oneself from contracting the virus. It is not very hard to stay protected from the virus such as wearing bug spray. These are very serious infectious, but they do not have cures either. Overall, there is no cure for the West Nile virus, but there is not a large demand for one either. Researcher: Sierra; Editor: Anu

Transmission

The West Nile Virus is a vector-borne disease meaning it is transmitted through mosquito bites (“West Nile Virus,” CDC). Other ways the disease can be transmitted is from mother to baby during pregnancy, blood transfusions, or in a laboratory setting where someone could be exposed to the virus (“West Nile Virus Infection”). However, these are rare cases (“West Nile Virus”). It cannot be transmitted person to person or animal to person through physical contact; you cannot obtain the virus from the consumption of an infected animal (“West Nile Virus Infection”). There is a specific transmission cycle for the West Nile virus, see Figure #4 (“West Nile Virus Infection”). The other carriers of this disease are mosquitoes, infected humans, horses, and other “dead end” hosts(“West Nile Virus,” Mayo). This means that it is hard for the infected animals to transmit the disease (“West Nile Virus Infection”). Another large factor are the amplifier hosts. Birds are the main amplifier host for the West Nile virus (“West Nile Virus Infection”). Amplifier hosts carry the disease and then develop a high concentration of the disease in their bloodstream (“West Nile Virus Infection”). This means that when a mosquito without the disease bites this bird, the mosquito becomes infected (“West Nile Virus Infection”). This does not occur within dead end hosts as the virus is not as concentrated in the bloodstream (“West Nile Virus Infection”). Because of these birds a cycle is created where mosquitoes infect birds and then the bird infect the rest of the mosquitos who are not yet infected (“West Nile Virus,” CDC). This never ending cycle creates a very difficult situation of solving the problem of WNV. Researcher: Ben; Editor: Jack

Figure #3: This shows the transfer of West Nile Virus. First, the birds get it, and when the mosquitos bite them, they get WNV. When the mosquitos bite the hosts, the contract West Nile Virus.

Figure #4: This shows the ways one can prevent themselves from contracting the virus. An example is getting rid of water collecting areas because mosquitos give birth on water. Notice how this is an average household in America, but this isn’t the case in all places.

World or NGO Engagement

Currently, there is no approved cure or vaccine for treatment of people infected with the West Nile Virus. There are medications that are approved for animals, however the FDA has not given permission for a drug that can be used on humans yet. On the plus side, there is a drug in testing currently that has had some positive results. It was first developed in the Oregon National Primate Research Center at Oregon Health & Science University (OHSU).

There are other groups dedicated to the prevention and curing of the West Nile Virus. Such as The West Nile Virus Working Group which is a compilation of multiple groups “conducting surveillance for this disease” (“Emerging Disease Issue”) Their focus is in Michigan but there are a multitude of groups across the nation and the world that work to prevent the spread of this disease. They focus on this by observing the bird population, many dead birds in a town is a sign of the West Nile Virus being spread locally. If there is a spike in bird deaths, the area knows to be more cautious. Another method is to try to manage the insect population or to use bug spray to not get bitten. Not only are the insects annoying, but they transmit many diseases including the West Nile Virus.Researcher: Jack; Editor: Ben

Solution

There has yet to be a practical solution to the West Nile Virus. One way to eradicate West Nile virus could be to break the agent-host connection by eradicating all carriers of the virus, birds and/or all of the hosts of the disease but this is not a feasible or appropriate option. Another solution could be to create a breed of mosquitoes immune to the disease and send them out into the world, but this is complicated to do as well. The mosquitoes would need to have the dominant gene that can be passed to their offspring so they can receive the immunity too so they’re not capable of getting and transmitting the virus. However, we can not be sure the new breed of mosquitoes would affect all other mosquitoes breeds. So as of today, there isn’t an effective or practical solution to the virus, but there is prevention.  People can prevent WNV infections by “using insect repellent and wearing protective clothing” (“Center for Disease Control”). People can also “mosquito-proof” their home by using screens on windows and by “by emptying standing water” around their home (“Center for Disease Control”) as seen in Figure #3. Having said that, depending on the location, climate and income of a person, they may or may not be able to acquire the preventions for WNV. For instance, if someone lives in the northern part of Brazil (near the equator), it’s easier for them to contract the virus and people near the equator wear less covering and protecting clothing. In Figure #5, it shows a map of where West Nile virus is most common, and it’s clear that the virus is prevalent in countries near the equator. In conclusion, there isn’t a practical solution to West Nile virus and though there are ways to prevent mosquito bites it depends on one’s current financial and geographical circumstance. Researcher: Sierra; Editor: Anu

Figure #5: “The approximate global distribution of West Nile virus, by country, state, and province, 2006.” (CDC) Figure appears courtesy of the Centers for Disease Control and Prevention.

Conclusion

Throughout the years West Nile virus (WNV) has extended from its first identified geographic range into other areas. In the past year, there were 2,038 reported cases of the West Nile virus in the US (West Nile Virus Disease Cases). Only 94 of the 2,038 people infected were reported dead (West Nile Virus Disease Cases). In third world countries, most of the cases go unreported because the people with the virus are in such rural areas. This makes it very difficult to record information on the virus in other countries. Because it is not very threatening, there are not too many groups dedicated to searching for a cure usable on people yet. Nonetheless, there is one in development first started at the Oregon National Primate Research Center at Oregon Health & Science University (OHSU). Given time and the advancement of modern technology, the finding of this cure will not be as difficult and is definitely achievable within a decade. The main issue of the West Nile virus is how easy it is for the disease to be transmitted. However there is little need to worry, as it is rare that those who are infected show any symptoms, and it is even rarer that they are in any serious danger. As years go on the number of people with the virus will decrease because more people are becoming educated about the dangers of this virus. The amount of people with the virus overtime has gone down, but there have been a few spikes. Researcher(s): All; Editor(s): All