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 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.
Precautions
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.
Ebolaviruses are not transmitted by
aerosol during natural EVD outbreaks. Without an approved vaccine, EVD prevention predominantly involves behavior modification, proper
personal protective equipment, and
sterilization/
disinfection.
On 6 December 2011, the development of a successful
vaccine against Ebola for mice was reported. Unlike the predecessors, it can be
freeze-dried and thus stored for long periods in wait for an outbreak. The research is reported in
Proceedings of National Academy of Sciences.
Endemic zones
The natural maintenance hosts of ebolaviruses are unidentified: primary infection may not necessarily be preventable in nature. Fruit bats are thought to be the natural hosts (primary source needed, but see e.g.
BBC). Thus, to avoid EVD, risk factors such as contact with
bats, nonhuman
primates, and
bush meat should be avoided.
During outbreaks
The most straightforward prevention method during EVD outbreaks is not touching patients, their
excretions, and
body fluids, or possibly
contaminated materials and utensils. Patients should be isolated, and medical staff should be trained and apply strict barrier nursing techniques (disposable face mask, gloves, goggles, and a gown at all times). Traditional
burial rituals, especially those requiring
embalming of bodies, should be discouraged or modified.
In the laboratory
Ebola viruses are
World Health Organization Risk Group 4 Pathogens, requiring
Biosafety Level 4-equivalent containment. Laboratory researchers have to be properly trained in BSL-4 practices and wear proper personal protective equipment.
reference: Wikipedia
