Friday, August 8, 2014


A man sellimg bush meat

       Ebola virus disease (EVD) or Ebola hemorrhagic fever (EHF) is the human disease caused by ebola viruses. Symptoms start two days to three weeks after contracting the virus with a fever, throat and muscle pains, and headaches. There is then nausea, vomiting and diarrhea along with decreased functioning of the liver and kidneys. At this point some people begin to have problems with bleeding.
The Ebola Virus
The disease is first acquired by a population when a person comes into contact with the blood or bodily fluids of an infected animal such as a monkey or fruit bat. Fruit bats are believed to carry and spread the disease without being affected by it. Once infection occurs, the disease may be spread from one person to another. Men who survive may be able to transmit the disease sexually for nearly two months. To make the diagnosis, typically other diseases with similar symptoms such as malaria, cholera and other viral hemorrhagic fever are excluded. The blood may then be tested for either antibodies to the virus, the viral RNA, or the virus itself to confirm the diagnosis.
Prevention involves decreasing the spread of the disease from infected monkeys and pigs to humans. This may be done by checking these animals for infection and killing and properly disposing of the bodies if the disease is discovered. Properly cooking meat and wearing protective clothing when handling meat may be helpful, as may wearing protective clothing and washing hands when around someone sick with the disease. Samples from people with the disease should be handled with an extra degree of caution.
There is no specific treatment for the virus with efforts to help people including giving the person either oral rehydration therapy or intravenous fluids. The disease has a high death rate: often between 50% and 90%.It typically occurs in outbreaks in tropical regions of Sub-Saharan Africa. Between 1976, when it was first identified, and 2014, fewer than 1,000 people a year have been infected. The largest outbreak as of 2014 is the ongoing 2014 West Africa Ebola outbreak, which is affecting Guinea, Sierra Leone, Liberia and Nigeria. The disease was first identified in the Sudan and the Democratic Republic of the Congo. Efforts are ongoing to develop a vaccine; however, none exists as of 2014.


Cases of Ebola fever in Africa from 1979 to 2008
Ebola virus first emerged in 1976 in outbreaks of Ebola hemorrhagic fever in Zaire and Sudan. The strain of Ebola that broke out in Zaire has one of the highest case fatality rates of any human virus, roughly 90%.
The name of the disease originated from one of those first recorded outbreaks in 1976 in Yambuku, Democratic Republic of the Congo (then Zaire) which lies on the Ebola River.
The Philippines and the United States had no previous cases of infection, and upon further isolation it was concluded to be another strain of Ebola or a new filovirus of Asian origin, and named Reston ebolavirus (REBOV) after the location of the incident.
Some scientists also believe that the Plague of Athens, which wiped out about a third of its inhabitants during the Peloponnesian War, may have been caused by Ebola. However, these studies are conflicting, and point to other possible diseases such as typhoid.

EVD is caused by four of five viruses classified in the genus Ebolavirus, family Filoviridae, order Mononegavirales: Bundibugyo virus (BDBV), Ebola virus (EBOV), Sudan virus (SUDV),Taï Forest virus (TAFV). The fifth virus, Reston virus (RESTV), is thought to be not disease causing for humans and therefore not discussed here.
EVD is believed to occur after an ebola virus is transmitted to a human index case via contact with an infected animal host. Human-to-human transmission occurs 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 such as needles. In the past, explosive nosocomial transmission has occurred in under-equipped African hospitals due to the reuse of needles and lack of implementation of universal precautions. Aerosol transmission has not been observed during natural EVD outbreaks. The potential for widespread EVD epidemics is considered low due to the high case-fatality rate, the rapidity of demise of patients, and the often remote areas where infections occur.
Other animals
In general, outbreaks of EVD among human populations result from handling infected wild animal carcasses. In general, declines in animal populations precede outbreaks among human populations. Since 2003, such declines have been monitored through surveillance of animal populations with the aim of predicting and preventing EVD outbreaks in humans. Recovered carcasses from gorillas contain multiple Ebola virus strains, which suggest multiple introductions of the virus. Bodies decompose quickly and carcasses are not infectious after three to four days. Contact between gorilla groups is rare, suggesting transmission among gorilla groups is unlikely, and that outbreaks result from transmission between viral reservoir and animal populations.
Outbreaks of EVD may have been responsible for an 88% decline in tracking indices of observed chimpanzee populations in 420 square kilometer Lossi Sanctuary between 2002 and 2003Transmission among chimpanzees through meat consumption constitutes a significant 5.2 (1.3–21.1 with 95% confidence) relative risk factor, while contact between individuals, such as touching dead bodies and grooming, do not.
Domestic animals
Ebola virus can be transmitted to dogs and pigs. While dogs may be asymptomatic, pigs tend to develop clinical disease.

Manifestation of Ebola begins abruptly with a sudden onset of an influenza-like stage characterized by general malaise, fever with chills, sore throat, severe headache, weakness, joint pain, muscle pain, and chest pain. Respiratory tract involvement is characterized by pharyngitis with sore throat, cough, dyspnea, and hiccups. The central nervous system is affected as judged by the development of severe headaches, agitation, confusion, fatigue, depression, seizures, and sometimes coma.
Cutaneous presentation may include: maculopapular rash, petechiae, purpura, ecchymoses, and hematomas (especially around needle injection sites). In general, development of hemorrhagic symptoms is indicative of a negative prognosis. However, contrary to popular belief, hemorrhage does not lead to hypovolemia and is not the cause of death (total blood loss is low except during labor). Instead, death occurs due to multiple organ dysfunction syndrome (MODS) due to fluid redistribution, hypotension, disseminated intravascular coagulation, and focal tissue necroses.
The average time between contracting the infection and the onset of symptoms is 13 days, but can be as long as 25 days.

All people infected show some extent of coagulopathy and impaired circulatory system symptomology. Bleeding from mucous membranes and puncture sites is reported in 40–50% of cases, while maculopapular rashes are evident in approximately 50% of cases. Sources of bleeds include hematemesis, hemoptysis, melena, and aforementioned bleeding from mucous membranes (gastrointestinal tract, nose, vagina and gingiva). However diffuse bleeding (i.e. heavy) is rare; occurrence is usually exclusive to the gastrointestinal tract.

A researcher working with the Ebola virus while wearing a BSL-4 positive pressure suit to avoid infection
Ebola viruses are highly infectious as well as contagious. Governments and individuals often quickly respond to quarantine the area while the lack of roads and transportation in many parts of Africa helps to contain the outbreak. Airline crews are trained to spot the symptoms of Ebola in passengers flying from places where the virus is found. Crews are told to quarantine anyone who looks infected.
As an outbreak of ebola progresses, bodily fluids from diarrhea, vomiting, and bleeding represent a hazard. Due to lack of proper equipment and hygienic practices, large-scale epidemics occur mostly in poor, isolated areas without modern hospitals or well-educated medical staff. Many areas where the infectious reservoir exists have just these characteristics. In such environments, all that can be done is to immediately cease all needle-sharing or use without adequate sterilization procedures, isolate patients, and observe strict barrier nursing procedures with the use of a medical-rated disposable face mask, gloves, goggles, and a gown at all times, strictly enforced for all medical personnel and visitors. The aim of all of these techniques is to avoid any person’s contact with the blood or secretions of any patient, including those who are deceased.
Vaccines have protected nonhuman primates. Immunization takes six months, which impedes the counter-epidemic use of the vaccines. In 2003, a vaccine using an adenoviral (ADV) vector carrying the Ebola spike protein therefore was tested on crab-eating macaques. The monkeys twenty-eight days later were challenged with the virus and remained resistant. A vaccine based on attenuated recombinant vesicular stomatitis virus (VSV) vector carrying either the Ebola glycoprotein or the Marburg glycoprotein in 2005 protected nonhuman primates, opening clinical trials in humans. The study by October completed the first human trial, over three months giving three vaccinations safely inducing an immune response. Individuals for a year were followed, and, in 2006, a study testing a faster-acting, single-shot vaccine began; this new study was completed in 2008. Trying the vaccine on a strain of Ebola that more resembles the one that infects humans is the next step.
The Food and Drug Administration has approved no candidate vaccines, the most promising whereof are DNA vaccines or derive from adenoviruses, vesicular stomatitis Indiana virus (VSIV) or filovirus-like particles (VLPs) because these candidates could protect nonhuman primates from ebolavirus-induced disease. DNA vaccines, adenovirus-based vaccines, and VSIV-based vaccines have entered clinical trials.
Ebola viruses are not transmitted by aerosol during natural EVD outbreaks. Without an approved vaccine, EVD prevention predominantly involves behaviour modification, proper personal protective equipment, and sterilization/disinfection.

Research by:
                                                                                                          EMMANUEL ADEBAYO
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