Emergent Viruses
Encyclopedia
An emergent virus is a virus that has adapted and emerged as a new disease/pathogenic strain, with attributes facilitating pathogenicity in a field not normally associated with that virus. This includes viruses that are the cause of a disease
which has notably increased in incidence; this is often a result of a wide variety of causes from both the influence of man
and nature
. Most emergent viruses can be categorized as zoonotic (an animal disease that can be transmitted to humans), this has the advantage of possibly having several natural reservoirs for the disease
.
. Most often the virus, due to selection pressure for an animal version of the strain of disease to mutate and therefore adapt to the infection of human hosts.
. During the 19th century poliovirus
became more prominent in populations across the world. Dense urban populations allowed the disease to propagate via close human
to human contact. In addition to this, technological advances meant that traveling became more common throughout the population essentially leading to increased transmission of the virus
. The situation became worse year upon year with increasing incidence of the disease
worldwide. The issue was not resolved until the introduction of a poliovirus vaccine
brought the situation under control. This example demonstrates how a disease can emerge in a population as a result of human influence. This examples also illustrates how an emergent virus can emerge and disappear by tackling the root cause. Poliovirus has been targeted for eradication
by the WHO
.
New emergent viruses are continually being discovered. Examples include: SARS and Avian influenza H5N1
.
Disease
A disease is an abnormal condition affecting the body of an organism. It is often construed to be a medical condition associated with specific symptoms and signs. It may be caused by external factors, such as infectious disease, or it may be caused by internal dysfunctions, such as autoimmune...
which has notably increased in incidence; this is often a result of a wide variety of causes from both the influence of man
Human
Humans are the only living species in the Homo genus...
and nature
Nature
Nature, in the broadest sense, is equivalent to the natural world, physical world, or material world. "Nature" refers to the phenomena of the physical world, and also to life in general...
. Most emergent viruses can be categorized as zoonotic (an animal disease that can be transmitted to humans), this has the advantage of possibly having several natural reservoirs for the disease
Disease
A disease is an abnormal condition affecting the body of an organism. It is often construed to be a medical condition associated with specific symptoms and signs. It may be caused by external factors, such as infectious disease, or it may be caused by internal dysfunctions, such as autoimmune...
.
Overview
The most important factor in the development of an emergent disease, to humans, is the ability to pass from animal host to humans. There is little to no occurrence of spontaneous new virus species development, although the possible exception commonly cited is Ebola virusEbola virus
Ebola virus causes severe disease in humans and in nonhuman primates in the form of viral hemorrhagic fever. EBOV is a Select Agent, World Health Organization Risk Group 4 Pathogen , National Institutes of Health/National Institute of Allergy and Infectious Diseases Category A Priority Pathogen,...
. Most often the virus, due to selection pressure for an animal version of the strain of disease to mutate and therefore adapt to the infection of human hosts.
Emergent virus infection factors
- Population movements
- Deforestation
- Irrigation
- Urbanization
- Increased long distance air travel
- Increased long distance air travel for livestock
- Migration
Poliomyelitis
Known to have existed for centuries with little incidenceIncidence (epidemiology)
Incidence is a measure of the risk of developing some new condition within a specified period of time. Although sometimes loosely expressed simply as the number of new cases during some time period, it is better expressed as a proportion or a rate with a denominator.Incidence proportion is the...
. During the 19th century poliovirus
Poliovirus
Poliovirus, the causative agent of poliomyelitis, is a human enterovirus and member of the family of Picornaviridae.Poliovirus is composed of an RNA genome and a protein capsid. The genome is a single-stranded positive-sense RNA genome that is about 7500 nucleotides long. The viral particle is...
became more prominent in populations across the world. Dense urban populations allowed the disease to propagate via close human
Human
Humans are the only living species in the Homo genus...
to human contact. In addition to this, technological advances meant that traveling became more common throughout the population essentially leading to increased transmission of the virus
Virus
A virus is a small infectious agent that can replicate only inside the living cells of organisms. Viruses infect all types of organisms, from animals and plants to bacteria and archaea...
. The situation became worse year upon year with increasing incidence of the disease
Disease
A disease is an abnormal condition affecting the body of an organism. It is often construed to be a medical condition associated with specific symptoms and signs. It may be caused by external factors, such as infectious disease, or it may be caused by internal dysfunctions, such as autoimmune...
worldwide. The issue was not resolved until the introduction of a poliovirus vaccine
Vaccine
A vaccine is a biological preparation that improves immunity to a particular disease. A vaccine typically contains an agent that resembles a disease-causing microorganism, and is often made from weakened or killed forms of the microbe or its toxins...
brought the situation under control. This example demonstrates how a disease can emerge in a population as a result of human influence. This examples also illustrates how an emergent virus can emerge and disappear by tackling the root cause. Poliovirus has been targeted for eradication
Poliomyelitis eradication
The global eradication of poliomyelitis is a public health effort to eliminate all cases of poliomyelitis infection around the world. The global effort, begun in 1988 and led by the World Health Organization, UNICEF and The Rotary Foundation, has reduced the number of annual diagnosed cases from...
by the WHO
Who
Who may refer to:* Who , an English-language pronoun* who , a Unix command* Who?, one of the Five Ws in journalism- Art and entertainment :* Who? , a 1958 novel by Algis Budrys...
.
New emergent viruses are continually being discovered. Examples include: SARS and Avian influenza H5N1
H5N1
Influenza A virus subtype H5N1, also known as "bird flu", A or simply H5N1, is a subtype of the influenza A virus which can cause illness in humans and many other animal species...
.