The official West Nile virus classification is that the species is a member the Flaviviridae family and belongs in the RNA virus Group 4 order. Within the Flaviviridae family, West Nile Virus, or WNV, is part of the viral Japanese encephalitis complex. The structure of the virus is similar to that of dengue fever and both are classified into the same system. The RNA structure is between 11,000 and 12,000 nucleotides and the virus appears with a smooth protein surface and a length of 45-50 nanometers. The genes of WNV include three structural proteins and seven non-structural proteins. Primarily, the virus is known to attack birds, but has also been found in the following animals: horses, cats, chipmunks, squirrels, rabbits, dogs, bats, and skunks. In addition, WNV has infected humans by way of mosquito bites.

In human cases, the WNV can take on three distinct and separate effects. An infection without symptoms may commonly be present, but a rare version of the infection manifests itself as a neuroinvasive disease named West Nile encephalitis or meningitis. The third possible appearance of West Nile virus symptoms is in the form of West Nile Fever, a mild febrile syndrome. It is this form of WNV that is most known. After contact has occurred, the virus incubates between two and eight days and then symptoms begin to appear. The experienced adverse reactions are similar to influenza and include the following complications: fever, chills, swollen lymph nodes, aching joints, headaches, pronounced sweating, weakness, and drowsiness. Some patients may also have gastrointestinal reactions such as nausea, vomiting, diarrhea, a loss of appetite, or the development of a rash in the torso region of the body. For the majority of sufferers, symptoms disappear after 7-10 days, but patients who experience lymph node problems may have problems for up to two months. The neuroinvasive version is much more dangerous and a person who contracts this infection may fall into a state similar to a coma where consciousness is severely impaired. WNV is not thought to be particularly threatening, but deaths have occurred from the virus. In the United States, mortality rate is estimated at 1%, but this figure may be inaccurate as nearly 80% of all cases have no symptoms and are not reported.

West Nile virus is currently a treatable and manageable infection. In addition, prevention by using mosquito repellent is an effective way for people to avoid contracting the infection. For cases in horses and other animals, a vaccine has been developed that successfully produces antibodies within the host’s body, thus creating an immunity to WNV. West Nile virus classification is relatively limited as the virus has not shown a considerable amount of mutation.

RNA virus classification refers to any species of virus that uses RNA rather then DNA as the functioning genetic material. Then International Committee on Taxonomy of Viruses uses the Baltimore system to group all relevant viruses into Group 3, Group 4, or Group 5. While the classification included a large number of virus species, the most known are influenza, hepatitis C, and Severe Acute Respiratory Syndrome, or SARS. All RNA viruses can be separated into single and double-stranded varieties. The single-stranded viruses are further broken down into negative-sense and positive-sense groups depending on the polarity of the RNA. The double-stranded viruses are more numerous than the single-celled variety and include the viruses that are potentially dangerous to host systems. Rotaviruses are included into this classification and are known to cause bluetongue virus in farm animals and gastroenteritis in youths. All RNA type viruses have the ability to mutate at extremely high rates because there is no proof-reading of DNA polymerases. The Baltimore system of classification differentiates between the different types of RNA viral sources by examination of the replication process.

Severe Acute Respiratory Syndrome, or SARS, is one of the most dangerous RNA virus types that attack humans. Caused by a coronavirus, SARS came close to a pandemic situation between November of 2002 and July of 2003. Infections began in China’s Guangdong province and quickly spread to a total of 37 countries worldwide. After the rapid infection became under control and the death totals calculated, it was estimated that SARS was responsible for 774 fatalities and 8,096 clinically confirmed cases. A vaccine was developed to combat the infection and there have been no reported cases since 2004. However, the World Health Organization has chosen not to consider the virus as being eradicated as it may return to human populations again. The vaccine was created by Chinese researchers and has been proven to produce effective antibodies in high numbers of patients. Sufferers of SARS who have recovered are at risk for major depressive disorder or the following physical conditions that have been linked to exposure to SARS: osteoporosis, femoral necrosis, and pulmonary fibrosis. The worldwide spread of the disease had other noticeable effects besides the health aspect. Tourism in Toronto and Chinese restaurant patronage in the United States were significantly lowered in response to the virus.

While the number of viruses labelled as RNA type are many, only a few are considered potentially life-threatening to humans. SARS, influenza, and hepatitis C are the most publicly known, but other variations include the Ebola, Mumps, Measles, Rubella, and Polio viruses. Further research of RNA virus classification will help scientists better understand these threats and the best treatments that can be used in response.

Polio virus classification has been occurring for an extremely long time, but recent efforts by the World Health Organization hope to make this a thing of the past. Artwork from ancient Egypt depicts people with polio symptoms, including withered limbs and young children who need the aid of canes to walk. Official classification of the polio virus did not occur until 1840 when Jakob Heine helped to identify the specific condition of polio. The spread of the condition was rampant until the latter part of the 20th Century. In 1988 the WHO and the Rotary Foundation announced a plan to completely eradicate polio infection in humans. The number of clinical cases has decreased dramatically, from 350,000 in 1988 to only 1,310 cases diagnosed in 2007. If polio is eradicated, it will only be the second time in human history that a disease has been erased by science, with the first being smallpox.

A polio infection results from contact with and Enterovirus appropriately named poliovirus. The virus is extremely contagious and person-to-person contact can easily spread the infection. Apart from human contact, the majority of cases occur from ingesting contaminated food or water. Upon entering a person’s body, the virus may attack the central nervous system in approximately 3% of cases. Of this 3%, less than 1% of cases progress to the stage of paralytic disease where a patient becomes paralyzed from the infection. While this type of polio rarely occurs, spinal polio does occur at a much higher rate. This variety is the most common and occurs when the virus infects a person’s spinal cord. Specifically, it attacks the area of the spine responsible for coordinating muscle movement. As the virus attacks the spinal cord, the nerve cells become inflamed which can cause permanent damage to the present neurons. In most cases, the infection is only damaging to one side of the body, most commonly paralyzing or debilitating the movement of a sufferer’s leg.

The WHO’s plan to eradicate polio is being completed with the use of a polio vaccine. The first vaccine used a blood plasma and was effective, but was not considered a reasonable option due to the shortage of available plasma. However, many medical professionals came together to develop a vaccine that would be effective and easy to produce. The result was two vaccines, one created by Hilary Koprowski and the other more famous one created by Jonas Salk. Salk’s vaccine is very effective, with a 99% immunity rate after three dosages of the medication. Albert Sabin’s version of the polio vaccine was licensed in 1962 and has since become the prevalent vaccine of choice. As the world gets closer to full eradication, polio virus classification may become an idea of the past.

Papilloma virus classification is relatively difficult because of the large number of individual species. As the nucleotide sequence that experts use to classify the virus can deviate by nearly 50% while still retaining the required five homologous genes, hundreds of different types of papilloma viruses can exist. Many of these types have been thoroughly examined, but more have yet to be officially classified. Different species of animal can incur the virus, but the virus generally mutates in a different manner depending on what type of animal has been infected. It is rare for an individual species to be transferred between species. The majority of papilloma viruses in animals either do not have any noticeable symptoms or result in benign tumors, called warts or papillomas. Types of these viruses have been isolated in turtles, birds, mammals, and humans.

The major difference between animal varieties and the human papilloma virus is that the human version has an increased capacity to turn cancerous, thus causing damage to the host person. The papilloma virus that infects humans generally attacks a certain skin or mucosal epithelium of the body which may include the following: genitals, hands, anus, mouth, hands, or airways. Most patients who have contracted the virus are not aware that they have it unless a physical wart appears. Infections are more common among younger women than any other group. Most warts and infections will disappear without external help in a matter of two years. However, those conditions that persist can be cause for concern as they can lead to cervical cancer if left untreated. This process may take between fifteen and twenty years, leaving plenty of time for detection and treatment. Despite this long period of time, the papilloma virus is still capable and does cause death. For the year 2008, it is estimated that 270,000 deaths occurred worldwide due to papilloma viruses. The majority of these deaths occurred in countries where adequate health care is not available to address the issue. The best way to prevent infection from a papilloma virus is by use of the papilloma virus vaccine. There are two products that are available to aid in prevention, Gardasil and Cervarix. These two vaccines protect a person from the strains that are responsible for most cancer-causing strains of papilloma. Administered as a series of injections, the vaccine takes half of a year to complete. A person who has already been infected with the virus will gain no benefit from the vaccine.

While the majority of papilloma viruses are not life-threatening to humans or animals, a patient who discovers a suspect wart should report the situation to a local doctor at their next visit. Early detection and treatment is the key to avoiding major problems resulting from the infection. As the virus mutates, more potent strains of papilloma may be discovered, but current strains are only dangerous if left untreated. Papilloma virus classification can be expected to increase as more and more specific strains are found in the different types of infected animals.

Although it is frequently mistaken as the common flu, influenza can take many forms but all influenza virus classification falls into three main groups: influenza A, influenza B, and influenza C. Influenza A is the most dangerous form of the virus, with the ability to mutate its genetic code 2-3 times faster than all other forms. Two viral surface proteins, hemagglutinin and neuraminidase, are used in classification to identify the 144 possible subtypes of an influenza A virus. Influenza B is still dangerous to humans but has not been responsible for the mass epidemics in the same manner that influenza A has. It does have the ability to mutate, but does so at a much slower rate. Influenza C is the last type of influenza virus. It is not common and has the slowest mutation rate.

The only influenza virus that has been known to cause major pandemics is type A. It was responsible for the Spanish flu outbreak, commonly known as la grippe, which occurred in 1918 and is also the cause of the modern H1N1, or swine flu, pandemic. The 1918 pandemic is thought to have been the cause of somewhere between 20 and 100 million people and featured an infection rate of nearly 50%. As the deadliness of this subtype has been proven, it is for this exact reason that the H1N1 influenza virus is being watched so closely. While the number of deaths resulting from the current H1N1 pandemic have come nowhere close to the numbers of the 1918 outbreak, it is still a cause for concern. Endemic in hogs and pigs, the virus does not always result in human influenza when it is transferred from swine to humans. A common misconception is that eating pork can cause transmission of the virus. If cooked properly, the meat has no risk of transmitting the virus. The classification of the specific H1N1 virus includes genetic data from the following four separate influenza viruses: North American swine flu, Asian and European swine flu, human influenza, and North American avian influenza. The virus has been declared a national emergency in the United States and the World Health Organization officially classified the virus as a pandemic in June of 2009. Since that time, 208 countries have reported confirmed cases of patients with the H1N1 virus. To date, there have been 13,554 deaths resulting from this particular strain.

While an influenza virus will commonly cause flu-like symptoms, most strains of the virus are not life-threatening. However, the evolution of the genetic makeup has made these viruses more resistant to traditional remedies and potentially more dangerous to humans. With the influenza virus classification of H1N1, the modern strain has proven its ability to cause a pandemic and it is still uncertain what the final outcome will be.

The herpes virus classification includes eight types of viruses that can affect humans and several types that can affect animals. The herpes virus belongs to the Herpesviridae family, a large family of DNA viruses. These viruses are classified by the place where they are situated in latent state.

The HHV-1 type, also referred to as herpes simplex virus-1 or HSV-1 is classified in the Alpha subfamily and it can mostly be found in the mucoepithelial cells. It is transmitted through close contact. The HHV-2 or HSV-2 is a virus usually spread by close contact, especially sexual contact. It primarily affects the mucoepithelial cells and it is responsible for the sexually transmitted disease called genital herpes. The HHV-3 or varicella zoster virus (ZVZ) is the third type of virus from the subfamily Alpha, that also infects the mucoepithelial cells and it can be transmitted through respiratory routes and close contact. All these three types of viruses are located in the neuron during their latency period. The HHV-4 is a virus from the Gamma subfamily, also referred to as Epstein-Barr virus (EBV) or lymphocryptovirus. It mostly affects the B cells as well as the epithelial cells and the most common way of transmission is through saliva. In the latent state, EBV is located in the B lymphocytes. The HHV-5 or Cytomegalovirus (CMV) is located in the monocytes, lymphocytes and others cells and it spreads through blood transfusions, transplants, close contact or congenital. It primarily affects the monocytes, lymphocytes and epithelial cells. These types of virus along with the HHV-6 and HHV-7 viruses causing roseola infantum in children are part of the Beta subfamily and they affect that T cells. Types HHV-6 and HHV-7 are located in the T lymphocytes and other cells. The last type, HHV-8 or Kaposi’s sarcoma-associated herpesvirus are herpesviruses that affect the lymphocytes and some other cells and they are transmitted through exchange of body fluids. The location of these herpesviruses in their latent state is unknown.

The viruses from the Herpesviridae family, or the herpesviruses represent the second most common cause of the human viral diseases, after influenza virus and the cold viruses. Once a person contracted it, the virus may remain in a latent form in the body and reactivate over the years, thus once a person got infected the virus remains in the body for life. However, most of the people have antibodies to this kind of viruses, apart from the HHV-8 herpesvirus. The HSV-1 and HSV-2 types are also known as herpes simplex viruses which are contagious and cause a cathegory of diseases called herpes simplex. Some of the conditions they can cause are the oral herpes, herpes keratitis, genital herpes or HSV Meningitis. Currently there are no cures known for these infections even though there are treatments available that can reduce its spreading.

The herpes virus classification includes viruses that affect only humans but there are few other types of viruses from the same family that affect exclusively animals and these belong mostly to the Alphaherpesvirinae subfamily.

Hepatitis virus classification includes seven types of hepatitis viruses, labeled with letters from the Latin alphabet. Hepatitis A virus or HAV affects the liver, causing an acute infectious disease called hepatitis A or just infectious hepatitis. The most common way of transmission is oral, through contaminated food or contaminated drinking water. The hepatitis A virus has an incubation period varying from two to six weeks. This condition affects millions of people every year all around the world especially in developing countries and poor regions. Once a person contracted the virus the immune system produces antibodies that confer immunity for next potential infections. The HAV outbreaks are successfully prevented by vaccination. HAV has only one serotype but several genotypes are known.

Hepatitis B virus (HBV) is responsible for the disease with the same name but it can also cause cirrhosis and hepatocellular carcinoma. Patients infected with HBV have a more increased risk to develop pancreatic cancer. There are four serotypes of the HBV virus, adr, adw, ayr and ayw, and eight genotypes, named from A to H. the severity of the disease and the possibility to evolve into more complicated forms are linked to the differences between the genotypes. There is a vaccine available to prevent infection with HBV.

Hepatitis C virus (HCV) is part of the Flaviviridae family and it is a single strand RNA virus, different than HAV and HBV. Even though they have similar names since they are all responsible for liver inflammation, these viruses are quite different. HCV is classified into six genotypes, labeled from 1 to 6, and subtypes for each genotype which are named with letters. Also each subtype is formed by many quasispecies. Currently there is no vaccine available to prevent infection with HCV and the genotype plays a very important role in the determination of the treatment followed. Usually, it is treated with an interferon-based therapy.

Hepatitis D virus or Hepatitis delta virus is a RNA virus which is activated only in the presence of the HBV virus. It can only be transmitted through an infection caused by HBV (at the same time) which is called co infection, or through the infection of a person who was infected with HBV in the past, which is called super infection. In 1955, the hepatitis E virus was documented the first time, a very small virus of only approximately 30 nanometers in diameter. In 1955 this virus caused an outbreak of hepatitis E in New Delhi, India. There is a vaccine available against HEV. In the 1990s it was believed that there existed a hepatitis F virus but after several studies the actual existence of the virus could not be proven. However, the most recently observed hepatitis virus is the HGB or hepatitis G virus. It was first documented in 1996 and it is believed to be distantly related to HCV.

Hepatitis virus classification includes many types of hepatitis viruses but in fact the most common are HAV which affects approximately 10 million people worldwide and HBV infecting more than 2 billion people worldwide.

Flu virus classification includes three types of influenza viruses from the Orthomyxoviridae family. Flu viruses are included in the Baltimore classification system in the group V, of RNA viruses and they are known as influenza viruses. This type of virus infects birds, mammals and humans.

There are three types of influenza virus, Influenza A, influenza B and influenza C. Influenza A is the type of influenza that is responsible for the largest pandemics and it is the type that mutates the fastest, 2 to 3 times faster than the other influenza viruses. The classification of influenza virus A is established based on the hemagglutinin (H or HA) and neuraminidase (N or NA) proteins that are visible on the surface of the virus. There are 16 types of hemagglutinin and 9 of neuraminidase so theoretically 144 subtypes of influenza A virus even though in practice only a part of these have been observed. It affects birds, mammals and humans and the most significant subtypes affecting humans are H1N1, H1N2 and H3N2 viruses. The H1N1 influenza virus is the one that caused the Spanish flu pandemic in the first decade of the 1900s and also the swine flu pandemic in 2009. The H5N1 subtype is the one thought to potentially cause a pandemic avian flu. Influenza B virus affects almost exclusively humans but it is not as common as influenza A. The virus is also responsible for influenza infections in seals. Due to its reduced antigenic diversity, immunity to this type of influenza is normally acquired for most of the people at early ages. Influenza B pandemics occur almost never. Influenza C generally affects humans and pigs and may be responsible for local epidemics although it is less common than the other influenza types.

The most recent pandemic was caused in 2009 by the swine flu virus, the H1N1 subtype of influenza A virus. The virus affects pigs but it can be transmitted to people who work with pigs, especially to those with a high degree of exposure. The farm workers are considered the most at risk of a zoonotic infection with this type of virus. The stomach flu or gastroenteritis is the inflammation of the gastrointestinal tract which has similar symptoms to the flu even though it is not caused by influenza viruses. The flu virus symptoms may involve fever, sore throat, chills, muscle pain and couching, and general discomfort. The flu caused by influenza can be life threatening if it evolves to pneumonia. The disease can produce nausea or vomiting in children.

The flu virus classification includes three types of influenza viruses, A, B and C from which only influenza C virus is believed to be the most stable virus type causing only mild diseases.

According to the old Ebola virus classification, the Ebola virus was considered a species of the Filovirus genus. In 1998 at the proposal of the Vertebrate Virus Subcommittee in the International Committee on Taxonomy of Viruses, the Ebolavirus along with the Marburg virus were classified in the Filioviridae family, representing two specific genera which are Ebola-like viruses and Marburg-like viruses. Today, in the official classification these two types of viruses are called Ebolavirus and Margburgvirus. The classification of the Ebolavirus includes different subtypes such as Zaire virus, Sudan ebolavirus, Reston ebolavirus, Cote d’Ivoire ebolavirus and the Bundibugyo ebolavirus.

The Zaire virus (also known as ZEBOV or Zaire Ebolavirus) is the virus with the highest fatality rate of up to 90%. The first outbreak of Zaire virus occurred in Yambuku in 1976 and this particular specie of viruses had more outbreaks than any other Ebolavirus species. The symptoms of the infection with Zaire virus are alike the symptoms of malaria so the patients were treated with quinine. It is believed that the virus was transmitted from an unsterilized needle used for an injection. The Sudan Ebolavirus (or SEBOV) is a specie of Ebola that spread from a worker in a cotton factory from Sudan. The scientists still do not know who the carrier was since all the animals and insects tested negative for the virus. The virus has an average rate of fatality situated between 50% and 60%. The Reston Ebolavirus or the REBOV was firstly discovered in the late 1980s during an outbreak of simian hemorrhagic fever virus in Reston, Virginia. The virus spread to the Philippines, Italy, Texas and it was also transferred to pigs in the Philippines. This virus does not affect humans, even if it is considered a level 4 organism but it is dangerous to monkeys. The first case was discovered in a crab-eating macaque in Covance Laboratories. Cote d’Ivoire Ebolavirus, also known as Ivory Coast Ebolavirus or Tai Ebolavirus was firstly discovered in 1994 among chimpanzees from the Tai Forest, Cote d’Ivoire, Africa. The virus was proved to be transmissible to humans after one of the scientists performing tests on the dead monkeys contracted it. She experienced symptoms similar to the dengue fever but after hospitalization she fully recovered within six weeks. Bundibugyo virus caused an outbreak in the district with the same name of Uganda in 2007. This is the most recently discovered type of Ebola and it has an average fatality rate up to 25%.

The most common Ebola virus symptoms are fever, muscle pain, headache and the inflammation of the pharynx but if the disease evolves vomiting and bloody diarrhea may occur. However, the symptoms may be different depending on the type of virus in the Ebola virus classification.

A virus classification means establishing a taxonomic system in which viruses are placed and named. There are different classification systems for viruses mostly due to the pseudo-living nature of viruses which does not allow a biological classification like there are for cellular organisms. Classifying viruses can be made depending on the phenotypic characteristics (morphology, nucleic acid type, mode of replication or hosts or the disease they are responsible for).

One of the classification systems is the one defined by the International Committee on Taxonomy of Viruses (ICTV) which began classifying the viruses in the 1990s. The system is based on the same taxon structure as the classification system for cellular organisms. The levels of this type of classification are the following: the Order (followed by the taxon suffix in italics; -virales), then the Family (-viridae), Subfamily (-virinae), Genus (-virus ) and Species. There are basically six orders that were established by the ICTV and these are the Caudovirales, Herpesvirales, Mononegavirales, Nidovirales, Picornavirales, and Tymovirales. According to the Baltimore viruses classification there are seven groups of viruses. This system was first established in 1971 and the viruses are placed on one of the seven groups depending on the combination of their nucleic acid, if they are single-stranded or double-stranded, sense and method of replication. The groups are labeled with roman numbers as following I: dsDNA viruses, II: ssDNA viruses, III: dsRNA viruses, IV: (+)ssRNA viruses, V: (-)ssRNA viruses, VI: ssRNA-RT viruses, VII: dsDNA-RT viruses. Classification of viruses is also made by the Holmes classification system, defined in 1948. This system classifies the viruses in three groups under a single order which is Virales. It is system of binominal nomenclature and the groups that the viruses can be placed into are group I (Phaginae; viruses that attack bacteria), group II (Phytophaginae; viruses that attack plants) and group III (Zoophaginae; viruses that attack animals). Other available system is the LHT System which uses the chemical and physical characteristics as a criteria for classifying the viruses.

The influenza virus is the virus causing infectious diseases in birds, mammals and humans. There are three types of influenza viruses (Influenza A, Influenza B and Influenza C) and they are part of the group V viruses in the Baltimore classification along with the deadly Ebola virus, Marburg virus and rabies. The group V viruses have genomes with a negative-sense single-stranded RNA. Influenza virus is part of the Orthomyxoviridae family along with the Isavirus (the virus causing Infectious salmon anemia) and Thogotovirus. The influenza viruses are the ones responsible for the seasonal flu and seasonal pandemics. The symptoms experienced by a person infected with influenza virus are usually fever, chills, sore throat, muscle pain, weakness and general discomfort. In severe cases can lead to pneumonia which can be life threatening.

The virus classification systems is actually a taxonomic system useful for scientists to detect easier the genome of a virus that has already been studied, the chemical and physical characteristics of it or the disease that it can cause.