Ebola virus disease (EVD) or Ebola hemorrhagic fever (EHF) is a disease of humans and other primates caused by an Ebola virus. Symptoms start two days to three weeks after contracting the virus, with a fever, sore throat, muscle pain and headaches. Typically, vomiting, diarrhea and rash follow, along with decreased functioning of the liver and kidneys. Around this time, affected people may begin to bleed both within the body and externally. 
LITRATURE REVIEW The ebolavirus life cycle begins with virion attachment to specific cell-surface receptors, followed by fusion of the virion envelope with cellular membranes and the concomitant release of the virus nucleocapsid into the cytosol. The viral RNA polymerase, encoded by the L gene, partially uncoats the nucleocapsid and transcribes the genes into positive-strand mRNAs, which are then translated into structural and nonstructural proteins. Ebolavirus RNA polymerase (L) binds to a single promoter located at the 3′ end of the genome.
Transcription either terminates after a gene or continues to the next gene downstream. This means that genes close to the 3′ end of the genome are transcribed in the greatest abundance, whereas those toward the 5′ end are least likely to be transcribed. The gene order is, therefore, a simple but effective form of transcriptional regulation.
The most abundant protein produced is the nucleoprotein, whose concentration in the cell determines when L switches from gene transcription to genome replication. Replication results in full-length, positive-strand antigenomes that are, in turn, transcribed into negative-strand virus progeny genome copy. Newly synthesized structural proteins and genomes self-assemble and accumulate near the inside of the cell membrane.
Virions bud off from the cell, gaining their envelopes from the cellular membrane they bud from. The mature progeny particles then infect other cells to repeat the cycle. The Ebola Virus genetics are difficult to study due to its virulent nature HYPERLINK “http://en. wikipedia. org/wiki/Ebola_virus_disease” \l “cite_note-Feldmann2005-40”  EVD is caused by four of five viruses classified in the genus Ebolavirus, family Filoviridae, order Mononegavirales. The four disease-causing viruses are Bundibugyo virus (BDBV), Sudan virus (SUDV), Tai Forest virus (TAFV), and one called simply, Ebola virus (EBOV, formerly Zaire Ebola virus)).
Ebola virus is the sole member of the Zaire ebolavirus species, and the most dangerous of the known Ebola disease-causing viruses, as well as being responsible for the largest number of outbreaks.  The fifth virus, Reston virus (RESTV), is not thought to be disease-causing in humans. The five Ebola viruses are closely related to the Marburg viruses. The virus may be acquired upon contact with blood or bodily fluids of an infected animal.  Spreading through the air has not been documented in the natural environment. 
Fruit bats are believed to carry and spread the virus without being affected. Once human infection occurs, the disease may spread between people, as well. Male survivors may be able to transmit the disease via semen for nearly two months. To make the diagnosis, typically other diseases with similar symptoms such as malaria, cholera and other viral hemorrhagic fevers are first excluded. To confirm the diagnosis, blood samples are tested for viral antibodies, viral RNA, or the virus itself. ANALYSIS OF THE TOPIC It is not entirely clear how Ebola is spread. 
EVD is believed to occur after an ebola virus is transmitted to an initial human by contact with an infected animal’s body fluids. Human-to-human transmission can occur via direct contact with blood or bodily fluids from an infected person (including embalming of an infected dead person) or by contact with contaminated medical equipment, particularly needles and syringes.  The potential for widespread EVD infections is considered low as the disease is only spread by direct contact with the secretions from someone who is showing signs of infection. 
The quick onset of symptoms makes it easier to identify sick individuals and limits a person’s ability to spread the disease by traveling. Because dead bodies are still infectious local traditional burial rituals may spread the disease.  Semen may be infectious in 1 / 6 survivors for up to 50 days. Medical workers who do not wear appropriate protective clothing may also contract the disease.  In the past, hospital-acquired transmission has occurred in African hospitals due to the reuse of needles and lack of universal precautions. 
Airborne transmission has not been documented during EVD outbreaks.  They are, however, infectious as breathable 0.8– to 1. 2-? m laboratory- generated droplets.  The virus has been shown to travel, without contact, from pigs to primates, although the same study failed to demonstrate similar transmission between non-human primates. Bats drop partially eaten fruits and pulp, then land mammals such as gorillas and duikers feed on these fallen fruits. This chain of events forms a possible indirect means of transmission from the natural host to animal populations, which has led to research towards viral shedding in the saliva of bats.
Fruit production, animal behavior, and other factors vary at different times and places that may trigger outbreaks among animal populations. [25Bats are considered the most likely natural reservoir of the EBOV; plants, arthropods, and birds have also been considered.  Bats were known to reside in the cotton factory in which the first cases for the 1976 and 1979 outbreaks were employed, and they have also been implicated in Marburg virus infections in 1975 and 1980.  Of 24 plant species and 19 vertebrate species experimentally inoculated with EBOV, only bats became infected. .
The absence of clinical signs in these bats is characteristic of a reservoir species. In a 2002–2003 survey of 1,030 animals including 679 bats from Gabon and the Republic of the Congo, 13 fruit bats were found to contain EBOV RNA fragments.  As of 2005, three types of fruit bats (Hypsignathus monstrosus, Epomops franqueti, and Myonycteris torquata) have been identified as being in contact with EBOV. They are now suspected to represent the EBOV reservoir hosts. 
Antibodies against Ebola Zaire and Reston viruses have been found in fruit bats in Bangladesh, thus identifying potential virus hosts and signs of the filoviruses in Asia. Between 1976 and 1998, in 30,000 mammals, birds, reptiles, amphibians and arthropods sampled from outbreak regions, no ebolavirus was detected apart from some genetic traces found in six rodents (Mus setulosus and Praomys) and one shrew (Sylvisorex ollula) collected from the Central African Republic. 
Traces of EBOV were detected in the carcasses of gorillas and chimpanzees during outbreaks in 2001 and 2003, which later became the source of human infections. However, the high lethality from infection in these species makes them unlikely as a natural reservoir.
Transmission between natural reservoir and humans is rare, and outbreaks are usually traceable to a single case where an individual has handled the carcass of gorilla, chimpanzee or duiker.  Fruit bats are also eaten by people in parts of West Africa where they are smoked, grilled or made into a spicy soup. DIAGNOSIS The medical history, especially travel and work history along with exposure to wildlife are important to suspect the diagnosis of EVD. The diagnosis is confirmed by isolating the virus, detecting its RNA or proteins, or detecting antibodies against the virus in a person’s blood.
Isolating the virus by cell culture, detecting the viral RNA by polymerase chain reaction (PCR) and detecting proteins by enzyme-linked immunosorbent assay (ELISA) is effective early and in those who have died from the disease. Detecting antibodies against the virus is effective late in the disease and in those who recover. During an outbreak, virus isolation is often not feasible. The most common diagnostic methods are therefore real time PCR and ELISA detection of proteins, which can be performed in field or mobile hospitals. 
Filovirions can be seen and identified in cell culture by electron microscopy due to their unique filamentous shapes, but electron microscopy cannot tell the difference between the various filoviruses despite there being some length differences. The symptoms of EVD are similar to those of Marburg virus disease.  It can also easily be confused with many other diseases common in Equatorial Africa such as other viral hemorrhagic fevers, falciparum malaria, typhoid fever, shigellosis, rickettsial diseases such as typhus, cholera, gram-negative septicemia, borreliosis such as relapsing fever or EHEC enteritis.
Other infectious diseases that should be included in the differential diagnosis include the following: leptospirosis, scrub typhus, plague, Q fever, candidiasis, histoplasmosis, trypanosomiasis, visceral leishmaniasis, 2 / 6 hemorrhagic smallpox, measles, and fulminant viral hepatitis.  Non-infectious diseases that can be confused with EVD are acute promyelocytic leukemia, hemolytic uremic syndrome, snake envenomation, clotting factor deficiencies/platelet disorders, thrombotic thrombocytopenic purpura, hereditary hemorrhagic telangiectasia, Kawasaki disease and even warfarin poisoning.
PROGNOSIS The disease has a high mortality rate: often between 50 percent and 90 percent.  As of April 2014, information from WHO across all occurrences to date puts the overall fatality rate at 60%-65%.  There are indications based on variations in death rate between countries that early and effective treatment of symptoms (e. g. , supportive care to prevent dehydration) may reduce the fatality rate significantly.  If an infected person survives, recovery may be quick and complete.
Prolonged cases are often complicated by the occurrence of long-term problems, such as inflammation of the testicles, joint pains, muscle pains, skin peeling, or hair loss. Eye symptoms, such as light sensitivity, excess tearing, iritis, iridocyclitis, choroiditis, and blindness have also been described.
EBOV and SUDV may be able to persist in the semen of some survivors for up to seven weeks, which could give rise to infections and disease via sexual intercourse. SIGNS AND SYMPTOMS Signs and symptoms of Ebola usually begin suddenly with an influenza-like stage characterized by fatigue, fever, headaches, joint, muscle and abdominal pain.  Vomiting, diarrhea and loss of appetite are also common.
 Less common symptoms include the following: sore throat, chest pain, hiccups, shortness of breath and trouble swallowing.  The average time between contracting the infection and the start of symptoms (incubation period) is 8 to 10 days, but it can vary between 2 and 21 days.  Skin manifestations may include a maculopapular rash (in about 50% of cases).  Early symptoms of EVD may be similar to those of malaria, dengue fever or other tropical fevers, before the disease progresses to the bleeding phase. In 40–50% of cases, bleeding from puncture sites and mucous membranes (e. g.gastrointestinal tract, nose, vagina and gums) has been reported. 
In the bleeding phase, which typically starts 5 to 7 days after first symptoms internal and subcutaneous bleeding may present itself through reddening of the eyes and bloody vomit.  Bleeding into the skin may create petechiae, purpura, ecchymoses and hematomas (especially around needle injection sites). Types of bleeding known to occur with Ebola virus disease include vomiting blood, coughing it up or blood in the stool. Heavy bleeding is rare and is usually confined to the gastrointestinal tract. 
In general, the development of bleeding symptoms often indicates a worse prognosis and this blood loss can result in death.  All people infected show some symptoms of circulatory system involvement, including impaired blood clotting.  If the infected person does not recover, death due to multiple organ dysfunction syndrome occurs within 7 to 16 days (usually between days 8 and 9) after first symptoms. [14EPIDEMIOLOGY The disease typically occurs in outbreaks in tropical regions of Sub-Saharan Africa.  From 1976 (when it was first identified) through 2013, the World Health Organization reported 1,716 confirmed cases.
 The largest outbreak to date is the ongoing 2014 West Africa Ebola virus outbreak, which is affecting Guinea, Sierra Leone,Liberia and Nigeria As of 13 August, 2,127 cases have been identified, with 1,145 deaths. 5]1976 The first identified case of Ebola was on 26 August 1976, in Yambuku, a small rural village in Mongala District in northern Democratic Republic of the Congo (then known as Zaire).  The first victim, and the index case for the disease, was village school headmaster Mabalo Lokela, who had toured an area near the Central African Republic border along the Ebola river between 12–22 August.
On 8 September he died of what would become known as the Ebola virus species of the ebolavirus.  Subsequently a number of other cases were reported, almost all centered on the Yambuku mission hospital or having close contact with another case.  318 cases and 280 deaths occurred in the DRC. The Ebola outbreak was contained with the help of the World Health Organization and transport from the Congolese air force, by quarantining villagers, sterilizing 3 / 6 medical equipment, and providing protective clothing.
The virus responsible for the initial outbreak, first thought to be Marburg virus was later identified as a new type of virus related to Marburg, and named after the nearby Ebola river. Another ebolavirus, the Sudan virus species, was also identified that same year when an outbreak occurred in Sudan, affecting 284 people and killing 151. 1995 to 2013 The second major outbreak occurred in 1995 in the Democratic Republic of Congo, affecting 315 and killing 254. The next major outbreak occurred in Uganda in 2000, affecting 425 and killing 224; in this case the Sudan virus was found to be the ebolavirus species responsible for the outbreak.
infected with REBOV tend to develop symptomatic disease, it has been shown that dogs may become infected with EBOV and remain asymptomatic. Dogs in some parts of Africa must scavenge for their food and it is known that they sometimes eat infected animals. Although they remain asymptomatic, a 2005 survey of dogs during an EBOV outbreak found that over 30% showed a seroprevalence for EBOV. ANTIBODIES During an outbreak 1999 in the Democratic Republic of the Congo, seven of eight Ebola patients who received blood transfusions from individuals who had previously survived the infection survived themselves.
 However, this potential treatment is considered controversial.  Intravenous antibodies appear to be protective in non-human primates who have been exposed to large doses of Ebola. CONCLUSION No specific treatment for the disease is yet available.  Efforts to help those who are infected are supportive and include giving either oral rehydration therapy (slightly sweet and salty water to drink) or intravenous fluids.  The disease has a high risk of death, killing between 50% and 90% of those infected with the virus. 
EVD was first identified in Sudan (now South Sudan) and the Democratic Republic of the Congo. The disease typically occurs in outbreaks in tropical regions of sub-Saharan Africa.  From 1976 (when it was first identified) through 2013, the World Health Organization reported a total of 1,716 cases.  The largest outbreak to date is the ongoing 2014 West Africa Ebola outbreak, which is affecting Guinea, Sierra Leone, Liberia and Nigeria.  As of 5 / 6 22nd August 2014, 2,615 suspected cases resulting in the deaths of 1,427 have been reported.  Efforts are under way to develop a vaccine; however, none yet exists.  POWERED BY TCPDF (WWW. TCPDF. ORG).