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Running head: AN EMERGING INFECTIOUS DISEASE
An Emerging Infectious Disease
Jill Lovano
Ferris State University
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AN EMERGING INFECTIOUS DISEASE
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Abstract
Emerging infectious diseases can pose many threats and are a constant concern of our public
health system. Understanding these diseases and how they are transmitted is vital in preventing
future epidemics. The West Nile Virus is an infectious disease that can be very debilitating for
someone who contracts it. This paper will discuss the West Nile Virus and its transmission,
diagnosis, and treatment. We will discuss ways to prevent you or a loved one from contracting
the virus.
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Emerging Infectious Disease
Mosquito season is soon to be upon us and with that comes the threat of an emerging
infectious disease. “Emerging diseases include outbreaks of previously unknown diseases or
known diseases whose incidence in humans has significantly increased” (National Institute of
Allergy and Infectious Diseases, 2010). Emerging infectious diseases can be those that have just
evolved or those that have changed their geographic range (Veenema, 2013, p.430).
Infectious diseases can become a very large threat to the public and are a continual
challenge for public health workers. “At any one time, at least one infectious disease is receiving
attention as a major threat to the public’s health” (Veenema, 2013, p.430). The West Nile Virus
(WNV) is one of the infectious diseases that can be deadly or debilitating for someone who
contracts it.
West Nile Virus
Mosquitos can carry several types of infectious diseases. WNV is an insect-borne
flavivirus and has been detected in at least 48 species of mosquitos (U.S. Geological Survey,
2014). Birds have been identified as being the host animal. The mosquito becomes infected by
the bird and then transmits the virus to humans while feeding on their blood. Understanding the
WNV and how it is transmitted is a big part of preventing large outbreaks that could threaten the
lives of many.
Transmission and Isolation
It is crucial to understand how WNV is spread in order to prevent it. Most often,
transmission is gained through the bite of an infected mosquito. The virus is carried in birds
which are the host animal. It is spread to humans through the bite of a mosquito through a
AN EMERGING INFECTIOUS DISEASE
mosquito-bird-mosquito transmission cycle. Birds are thought to be the reservoir or amplifying
host (Pauli, et al., 2012).
The WNV cannot be spread through casual human contact; however the virus has been
known to be spread from human to human through blood transfusions, organ transplants, and
from mother to child during pregnancy or breast feeding (Centers for Disease Control and
Prevention, 2013).
In 2002, 42 WNV infections were thought to be contracted through transfusions of
blood. Transmission of the virus has been linked to red blood cells, platelets, and fresh-frozen
plasma (Bledsoe, 2004). Several rapid tests have been invented to help keep the blood supply
safe. Using nucleic acid testing can detect the virus in individuals before they are symptomatic
and help to keep blood supplies virus free.
The first report of utero transmission was reported in 2002. The child was born with
significant neurological abnormalities but it could not be determined if this was caused by the
WNV. The virus can also be present in breast milk and can infect the breast feeding infant
(Bledsoe, 2004).
The WNV was first isolated in the West Nile district of Uganda in 1937 from a woman
infected with the virus. Human infections have been reported in many countries over the past 50
years (World Health Organization, 2011). The WNV presented itself in the United States in
1999 when the virus was imported from Israel and Tunisia arriving in New York. This started a
large outbreak that spread throughout the United States (World Health Organization, 2011).
Clinical Presentations
WNV is a neuroinvasive disease which is able to cross the blood-brain barrier and
replicate and elicit pathology in the brain (Petersen, Brault, & Nasci, 2013). The WNV can be
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asymptomatic for most people. The World Health Organization estimates that about 80% of
those infected will show no signs or symptoms (2011).
In minor cases, the virus can cause fever, nausea, vomiting, headache, body aches, joint
and muscle pain and malaise. Over half of these will also report having a rash. The virus can
cause more severe cases or neuroinvasive diseases. The virus invades the nervous system causing
meningitis or encephalitis. The symptoms of the more severe cases are headache, fever, stiff
neck, disorientation, coma, tremors, convulsions, muscle weakness, and paralysis (Goodman &
Livingston, 2012).
Symptoms of WNV usually take 3 to 14 days before they begin. The symptoms usually
last 3 to 6 days but others have reported being sick for weeks. The more severe cases can last for
weeks and leave behind permanent damage. In some cases, it can cause death (Goodman &
Livingston, 2012).
Diagnosis
It is important to consider WNV for any patients that have encephalitis or meningitis with
an unknown origin. Diagnosis of the WNV can be made through laboratory blood and
cerebrospinal fluid tests. These tests detect WNV specific IgM antibodies (Centers for Disease
Control and Prevention, 2013). Once the body becomes infected with the virus, it produces
antibodies to help fight the infection. These tests allow for the detection of the specific
antibodies of WNV.
The virus can also be detected through the use of computed tomography or magnetic
resonance imaging scans of the head (Goodman & Livingston, 2012). These tests can detect
inflammation or changes in the brain that are caused by the neuroinvasive infection.
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Therapy
There are no FDA approved treatments for WNV and no vaccines. Vaccines are available
for horses but none have been approved for humans. Researchers are working on a live vaccine
for humans but it is still in the early stages (Filette, Ulbert, Diamond, & Sanders, 2012). Most
people infected with WNV will go without symptoms. Those that have minor symptoms will be
given supportive treatment. Treatment is much like that of the influenza virus. Individuals can
be treated with over the counter pain medications to relieve headache and discomfort. They
should get plenty of rest and keep hydrated until the virus runs its course.
More severe cases may need hospitalization for intravenous fluids and pain control
(Centers for Disease Control and Prevention, 2013). These individuals may have confusion
which could jeopardize their safety and may need specialized care in order to prevent injury.
Researchers are working on an interferon treatment for those who have developed
encephalitis due to WNV. Research is indicating that this treatment may help improve recovery
in these individuals (Mayo, 2015).
The best thing to do is to try to avoid being bitten when it is mosquito season. Use insect
repellents that contain DEET and wear clothing that covers the legs and arms. Avoid going
outside during peak times such between dawn and dusk and keep window screens maintained
and tight fitting. Those individuals that have an occupation that requires them to be outside
should be sure to protect themselves in the ways mentioned above.
Stagnant water should be eliminated because this is a breeding ground for mosquitos
(Haley, 2012, p.1326). Clean out rain gutters and change the water in bird baths to help eliminate
these breeding pools.
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Dead birds can be a sign that WNV is circulating between mosquitos and birds, so be
sure to report any sighting of dead birds to your local authorities. Over 130 different species of
birds are known to be infected by the WNV, but not all birds that are infected will die.
Analysis of Evidence
The WNV is an emerging disease because of the incidence of increased infection in
humans. The WNV has been the cause of over 12,000 cases of encephalitis and meningitis and
has caused 1,100 deaths (Murray, Mertens & Despres, 2010). Since the introduction of WNV in
North America, it has been detected in 48 species of mosquitos, 250 species of birds, and 18
mammalian species which include humans (Wertheimer, 2012).
The WNV started in the United States in 1999 and since then has spread across the U.S.
and southern Canada. In 2010, the first cases of the virus in humans were reported in Greece.
The WNV has also been reported in the Caribbean and Central and South America. The virus is
now considered an endemic from the Americas and Canada to Argentina (Pauli, et al., 2012).
Research on the WNV has been done through collecting data over periods of time.
Human surveillance was used to describe and quantify the spread of the virus. The number of
cases of WNV was determined by reports from the Centers for Disease Control. These cases met
the CDC’s case definition of clinical disease with laboratory confirmation to provide accuracy.
Evidence suggests that WNV is an emerging disease that can have devastating
neurological effects. Most research was obtained through gathering information from previous
years and public surveillance.
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Factors Promoting Disease
Factors that promote WNV could be related to society and the environment. It is hard to
determine when and where an outbreak will occur because of the factors that are involved with
promoting the disease. Precipitation and warmer temperatures promote the disease by shortening
the incubation time from infection to infectiousness in the mosquito and increase the
transmission efficiency to birds (Petersen, Brault, Nasci, 2013). In the United States most cases
of WNV occur between the months of July and September. Reports show a significant increase
during those months with a peak incidence in August (Lindsey,et al., 2012). Areas with forests or
urban areas seem to pose a higher risk.
The WNV has highest incidence in the Midwestern and southern states, so geographic
region does play a part. The virus is also present in Africa and the Middle East (Mayo, 2015).
This indicates that warmer climates have a higher incidence of WNV. Individuals that live in
areas with standing water such as swamps may need to work with other members of the
community to control the mosquito population. Pesticides may need to be used to prevent the
infestation.
Age can also be a factor in promoting WNV. Elderly individuals have a higher risk of
serious illness and death. This is thought to happen because of the inability of the elderly to
develop an effective immune system (Lindsey, et al., 2012).
Human behavior is another factor that can promote the disease. Outdoor activities, the
use of repellents, and even the use of air conditioners can promote the disease in humans
(Lindsey, et al., 2012). Communities should be educated on the risk of WNV and in ways to
prevent its transmission. The number of mosquitos can also be a factor, if there are fewer
mosquitos there is less of a chance of being bitten by an infected one. Communities should work
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together to control the infestation of mosquitos. Aerial spraying of pesticides can help reduce the
numbers.
Individuals who have a weakened immune system are at a higher risk of contracting the
virus. Those who suffer from chronic diseases such as cancer, diabetes, heart disease, and
alcoholism are also at a greater risk of contracting the virus with more serious health effects
(Mayo, 2015). An important factor in determining if a microbe will cause a disease is host
susceptibility (Veenema, 2013, p.431).
Conclusion
Emerging infectious diseases are a continual concern for public health officials. They
can lead to epidemics and pandemics and pose a great health threat throughout the world. The
spread of the WNV has proven that it is an emerging infectious disease. More and more cases are
being reported throughout the world.
It is important to be aware of the WNV and ways to prevent it. Spread of the WNV is
effectively managed with effective mosquito control. Communities should work together to
control the mosquito population and to prevent the threat of such a disease. Through education
and understanding we may be able to prevent future emerging infectious diseases that could
potentially wipe out the population of the world.
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