West Nile Virus example essay topic

Virus Overview The virus was first thought about in 1883 when A. Mayer was seeking to find the cause of the tobacco mosaic disease. Though he was unable to see them with the microscopy of his day, he postulated that a small agent caused the disease. D. Ivanowsky, later tried tests as well and also concluded that it was a disease caused by something smaller than they could see. The virus was first found and discovered in 1935 by Wendell Stanly. He was able to crystallize the virus, now known as the tobacco mosaic virus.

The smallest viruses are only 20 nm in diameter, smaller even than a ribosome in a cell. Though not a living thing, viruses are infections particles consisting of only the viral genes in closed in a shell of protein. Their genomes consist of double-stranded DNA, double stranded RNA, single-stranded DNA, or single stranded RNA. The name of a virus, DNA or RNA, is based on the type of nucleic acid that composed its genome. The smaller viruses have only a few genes while others have several hundred. The capsid is a protein shell that enclosed the viral genome and comes in many shapes and sizes.

They are composed of many protein subunits called, although the actual numbers of different kinds of protein are few. Many viruses have a membranous envelope that covering their capsid. Composed of the host cell's membrane, the membrane helps with the "life" cycle when the virus is taking over the host cell. The question of whether or not a virus is a living object or a complex protein is often fuzzy. When isolated from a host cell, a virus is unable to replicate, produce energy, or any other activities required for life.

This makes them nothing more than a protein coated set of genes in transit from one host to another, a biological gene transport mechanism. A virus is only able to "infect" a limited range of host cells, called its host range. This process is referred to as the lock and key fit between proteins on the outside of the virus and the receptor molecules on the surface of the cell. Some have a host range that can infect many species while others only one type of bacteria. A virus that is designed to kill bacteria are phages, or bacteriophages.

The hostile take over of a host cell is the Lytic cycle or the cycle. The lytic cycle is the process where the virus attaches to the cell, releases its viral genes and takes over the cell. Once control of the cell is achieved, the genes tell the cell to start producing more viral parts and assemble them. Eventually, so many new viruses are produced, the cell swells and eventually bursts, spewing hundreds or even thousands of new viruses. The cycle, is nearly the same as the lytic cycle, though a bit more controlled and hidden. The gene code splices into the cells code and lies dormant, waiting for the time to then begin producing itself.

This way, the cell does not die after infection until the genes take over and begin the lytic cycle. Many variations on the viral infect scheme are among animal viruses. There are two variations, viruses with envelopes and viruses with RNA genomes, though some have both of these features. Classes of Animal VirusesdsDNA Papilloma, Herpes, Small Pox ssDNA ParvovirusdsRNA Diarrhea viruse RNA + Polioviru RNA - Rabies, measle RNA DNA leukemia Viruses with an envelope outside the capsid use the membrane to help enter the host cell. This membrane is generally a lipid bi layer, with glycoproteins protruding from the surface. The viruses that infect humans are many, and are a constant threat to the health of the human population.

Ebola, AIDS, the common cold, Herpes, and the West Nile Virus, are but a few of the animal viruses that are a hazard to humans. The Ebola virus is currently one of the world's most deadly viral infections. While the AIDS virus is classified as a level 2 pathogen, Ebola is rated at a four. The infected victim of Ebola staggers, disoriented and exhausted, and collapses in a fever, which is known as the Hemorrhagic fever. The fever is characterized by weakness, muscle pain, headache and sore throat. The victim's eyes turn bright red, and vomits blood.

The tongue peels, and the heart muscle becomes soft. When the victim is infected with the virus, the virus first triggers a combination of blood clots and hemorrhages. The patient's bloodstream throws clots, and the clots lodge everywhere, especially in the spleen, liver, and brain. It then settles in the victim's throat. Capillary leakage appears to lead to loss of intra vascular volume leading the patient to fall into shock and acute respiratory disorder.

The virus kills its victims quickly, often before it even can infect others due to the long incubation period. The incubation period for the Ebola virus ranges from 2 to 21 days, depending upon the method of infection. The Ebola virus can be diagnosed with laboratory testing of blood specimens under maximum containment conditions, as the high risk of infection to those handling infected blood remains dangerous and hazardous to them. Infection of this virus occurs through the blood and is replicated in organs like the Liver, lymphatic organs, and the kidneys. However, it is also spread through close personal contact with the infected person. Normally, the wild spread of Ebola virus takes place among hospital care workers or family members who were aiding an infected person.

The West Nile Virus is of the Flaviviridae family and contains nearly 10,000 RNA basis. To the right is a electron Microscope image of the West Nile virus. The most serious manifestation of the West Nile virus infection is fatal encephalitis (inflammation of the brain) in humans and horses, as well as mortality in certain domestic and wild birds. West Nile virus was first isolated from a febrile adult woman in the West Nile District of Uganda in 1937. The ecology was characterized in Egypt in the 1950's. The virus became recognized as a cause of severe human (inflammation of the spinal cord and brain) in elderly patients during an outbreak in Israel in 1957.

Equine disease was first noted in Egypt and France in the early 1960's. The virus did not come to America until 1999 and by the current CDC charts, over 2000 people in America are infected and over 150 have died.