1. 8. Dengue Virus
The causative agent of the dengue disease is the dengue virus (DENV), a group of four flaviviruses that are closely related but antigenically distinct. They are hypothesised to have evolved independently from ancestral sylvatic viruses between 100-1,500 years ago (Wang et al., 2000). The four groups are known as serotypes and denoted as dengue virus type 1 (DENV-1), dengue virus type 2 (DENV-2), dengue virus type 3 (DENV-3) and dengue virus type 4 (DENV-4).
1. 8. 1. Taxonomy
There are three genera in the Flaviviridae family (formerly known as group B arboviruses) namely Flavivirus, Pestivirus and Hepacivirus. The dengue virus is a member of the genus Flavivirus which consists of 55 identified virus species (ICTVdB, 2006). The word Flavi is a derivation from the Latin “flavus” which means “yellow” and the type species of the genus is a yellow fever virus (YFV). The flaviviruses are thus named due to the jaundice observed in yellow fever patients. Many flaviviruses are important human pathogens, most notably the dengue viruses, yellow fever virus, Japanese encephalitis virus (JEV), West Nile virus (WNV) and tick-borne encephalitis virus (TBEV). The flaviviruses are predominantly transmitted by mosquitoes and ticks, whereas some have no known vector. Dengue was one of the groups classified when early researchers divided the flaviviruses serologically into eight antigenic complexes using cross-neutralization tests. However, many viruses, for example the prototype of the genus YFV, could not be affiliated with any complexes (Calisher et al., 1989). When sequence data became available, phylogenetic inference from molecular data showed agreement with the antigenic complex classification. In addition, it revealed the ...
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...he viral fitness. Most of the mutations in DENV genomes are deleterious which plays an important role in DENV evolution. Another major factor for DENV adaptation is diversification which linked to transmission in various geographical regions.
Four dengue virus, serotype can co-circulate in the endemic areas because the immunity to one serotype does not protect from the infection by a heterologous serotypes. This is likely a result of selection that was driven by the restrictive effects of the cross-protective antibodies raised against heterologous serotypes. The dengue virus strains, which are able to escape this neutralization process has a significant competing advantage and become the dominant lineages. This evolutionary adaptation not only enabled the co-circulation of all 4 serotypes but also has a great influence to their pathogenicity for humans.
There is no definitive history or discovery date, but it is assumed that Yellow Fever originated in Africa and was brought to the Americas by Aedes aegypti mosquitoes “hitchhiking” on trade and slave ships. The first believed outbreak happened in 1648 in the Yucatán. It is “believed” because early documentation of disease and illness was not thoroughly investigated or described, they could have been caused by one thing or another. There is ...
This virus searches for a new vulnerable host in order to survive and carry the disease to the next victim. The critical aspect around the spread of a virus is how drastically the reproduction process occurs. Without being controlled, the contamination throughout any species causes the spread to take place in a toxic way, “On day one, there were two people. And then, four, and then, sixteen. In three months, it’s a billion.
Cytomegalovirus (CMV) is the most common virus in the United States that can infect almost any individual. Cytomegalovirus is also referred to as Herpesvirus-5, which belongs to a branch of Herpesviridae family. Herpesviridae has a spherical shape that contains four significant elements that are important to the viron. The four elements are the core, tegument, capsid and the envelope. Alphaherpesvirinae, Betaherpesvirinae and Gammaherpesvirinae are three subfamilies which belong to Herpesviridae. Cytomegalovirus belongs to the Betaherpesvirinae family, which also include Muromegalovirus and Roseolovirus. The Alphaherpesvirinae subfamily includes Simplexvirus, Varicellovirus, Mardivirus and Iltovirus genera. The Gammaherpesvirinae subfamily contains Lymphocryptovirus and Rhadinovirus genera. The diameter size of the virus is based on each specific family; however, the core remains the same throughout the species, which contains single layer of double stranded DNA tightly condensed in the capsid. In the tegument component, there are 30 or more viral proteins that are shapeless that encompass the capsid. Out of the four major components, the tegument has the most poorly defined structure. On the other hand, the capsid is a well-defined structure that is an icosahedron, which is composed of 162 capsomeres, 12 of which are pentons and 150 are hexons (1). Last but not least, the liquid envelope surrounds the tegument with approximately 10 glycoprotein and cellular proteins. Each subfamily under the herpesviriade has its own arrangement between the liquid envelop and the tegument layer.
The discovery of yellow fever would have not been possible if people had not put aside their misconceptions of where diseases originated. Diseases in olden time were believed to be divine punishment to people who had committed bad deeds, and therefore not much was done to try to find cures for diseases like yellow fever. As defined by the World Health Organization, yellow fever an acute viral hemorrhagic diseases transmitted by infected mosquitoes, and a common characteristic of this disease is the development of jaundice which gave it the name "yellow" fever. The mosquito responsible for the transmission of the disease is the female Aedes aegypti mosquito. Her transmission of the disease occurs as a result of it biting an infected host and inside her body the virus multiplies, and afterwards if the mosquito bites someone that person becomes infected.
Polio is a viral disease. It cripples thousands of people and infects even more every year. Even though millions are inoculated, and the polio disease has been successfully purged from hundreds of countries still thousands of people and developing countries are infected and still people are dying. According to the World Health Organization (WHO) polio affects the Central Nervous System, or CNS; by infesting the intestines and transmitting it into the nerves thought the blood vessels. There the virus spreads through the nerve cells to the brain stem or other motor units, while forever damaging the nerves.
The virus is primarily spherical shaped and roughly 200nm in size, surrounded by a host-cell derived membrane. Its genome is minus-sense single-stranded RNA 16-18 kb in length. It contains matrix protein inside the envelope, hemagglutinin and neuraminidase, fusion protein, nucleocapsid protein, and L and P proteins to form the RNA polymerase. The host-cell receptors on the outside are hemagglutinin and neuraminidase. The virus is allowed to enter the cell when the hemagglutinin/ neuraminidase glycoproteins fuse with the sialic acid on the surface of the host cell, and the capsid enters the cytoplasm. The infected cells express the fusion protein from the virus, and this links the host cells together to create syncitia.
The chikungunya virus could not only have a devastating impact on the tourism of these countries, but also it could hurt other parts of their economies. To start off, with the chikungunya virus would also come public health costs which could potentially hurt the economy as these countries would have to figure out how to prevent chikungunya(Lalta, Stanley). Prevention could only be done through spending money on research and medicine that's necessary in order to stop chikungunya. Estimated amounts show that “total treatment and preventions for the Chikungunya Virus with a population of 1.3 million people would cost 13.2 million dollars in U.S. currency”, a very expensive amount that many poorer countries cannot bear. Symptoms of CHIK such as severe joint pain, headache, or arthritis would require real medicine to help a person stay healthy. Arthritis in limbs has been known to be one of the most severe symptoms associated with the chikungunya virus. By definition, it is
Lyme disease is one of the seven most common diseases reported in the United States to the CDC annually (www.cdc.gov). The rates have gone from 10,000 cases in 1992 to over 30,000 cases in 2009. 95% of these cases were found in the northeast and Midwest regions of the United States (Committee on Lyme Disease, 2011) . More cases happen in this area of the country due to the close proximity of deer to population. The bite itself isn’t the problem, rather the pathogen being spread in mammals from the bite. Lyme disease occurs when a tick penetrates the skin of mammals and the spirochete Borrelia burgdorferi enters. Borrelia burgdorferi is carried by ticks named the Ixodes dammini, which is the main vector for Lyme disease. These may also be known as I. scapularis, and may be found on deer (Schilling-McCann, 2010). ¬¬¬In addition to Lyme Disease, ticks may also carry Rocky Mountain Spotted Fever or Tularemia (Smeltzer et al, 2010).
The Ebola virus is a member of a family of RNA viruses know as Filoviruses, because they resemble thread. Filoviruses are among the most mysterious viruses in the world because their natural history remain unknown and their pathogenesis poorly understood. The family consists of Ebola and Marburg viruses. Marburg and Ebola both cause hemorrhagic fevers (www.encyclopedia.com).
This particular species thrives in standing water, which occurs with higher frequency in populations with high density and low economic status. There will be fewer opportunities for the virus to burn out, and
Hvistendahl, M, Cohen, J et. al. 2013. ‘New Flu Virus in China Worries and Confuses’ Science 340: 129-130
In the story it talks about how in Texas only 64 outbreaks of dengue happened and how in Mexico 60,000 outbreaks happened, they think so many outbreaks happened in Mexico because the people that live in Texas have screens on their doors and windows but can easily add screens to the houses in Mexico. I don't think the OX513A is a safe
Viruses have emerged as causes of foodborne disease, according to data compiled by the Centers for Disease Control and Prevention. Viruses cause a wide range of diseases in plants, animals and humans. These infections do not occur at random: each group of viruses has its own typical host range and cell preference. Viruses were probably always a cause of food borne disease; however with recent developments in detection we are now able to confirm the presence of viruses. Previously, those outbreaks may have been recorded as having an unknown causative agent.
According to Darwin and his theory on evolution, organisms are presented with nature’s challenge of environmental change. Those that possess the characteristics of adapting to such challenges are successful in leaving their genes behind and ensuring that their lineage will continue. It is natural selection, where nature can perform tiny to mass sporadic experiments on its organisms, and the results can be interesting from extinction to significant changes within a species.
DENV is one of the world’s most geographically prevalent arthropod-borne viruses. Its geographical distribution is intrinsically attached to the range and habitat of its principal vector mosquitoes (Figure 1.5). Dengue infections are reported in more than hundreds of tropical and sub-tropical countries worldwide, mostly in urban and semi-urban areas where the vectors for dengue virus are commonly found. Dengue is hyper-endemic in many of these urban cores with co-circulation of multiple dengue virus serotypes. In non-tropical regions, dengue is usually spread by the international travellers that have visited dengue-endemic areas (Malavige GN et al.,2004).