The 2014 Ebola outbreak across Guinea, northern Liberia, and Sierra Leone is fuelling concern worldwide. According to the Centers for Disease Control and Prevention (CDC), with over 4,087 laboratory confirmed cases of Ebola virus this year alone and around 3,431 deaths from the epidemic, this is the worst outbreak ever. Medical News Today examines the effects of Ebola on the human body and the current concerns people may have about the virus.
WHO organized an expert consultation to assess the status of work to test and eventually license two promising candidate Ebola vaccines.
The first is cAd3-ZEBOV, which has been developed by GlaxoSmithKline in collaboration with the US National Institute of Allergy and Infectious Diseases. It uses a chimpanzee-derived adenovirus vector with an Ebola virus gene inserted.
The second, rVSV-ZEBOV, was developed by the Public Health Agency of Canada in Winnipeg with NewLink Genetics company, located in Ames, Iowa. The vaccine uses a weakened vesicular stomatitis virus, a pathogen found in livestock; one of its genes has been replaced by an Ebola virus gene.
The next step is to make these vaccines available as soon as possible - and in sufficient quantities - to protect critical frontline workers and to make a difference in the epidemic's future evolution.
When an Ebola infection occurs in humans, the virus can be spread in several ways to others. Above is a list of ways Ebola can and cannot be transmitted.
CDC confirmed on September 30, 2014, the first case of Ebola to be diagnosed in the US in a person who had traveled to Dallas, TX from West Africa.
First case of Ebola is diagnosed in the US.
CDC have responded by ensuring experts will assist state and local health departments to find, assess, and assist everyone who came into contact with the Ebola patient between the time he became symptomatic (before having symptoms, people with Ebola cannot spread the infection) and the time he was placed in an isolation ward.
"We are stopping Ebola in its tracks in this country," said CDC Director Tom Frieden, MD, MPH, "We can do that because of two things: strong infection control that stops the spread of Ebola in health care; and strong core public health functions to trace contacts, track contacts, isolate them if they have any symptoms and stop the chain of transmission. I am certain we will control this."
Experts from the WHO and Imperial College, London, say that unless Ebola control measures in west Africa are enhanced quickly, numbers will continue to climb exponentially.
It is predicted that more than 20,000 people will have been infected by early November, according to a new article in the New England Journal of Medicine released 6 months after WHO was first notified of the outbreak in West Africa.
On September 24, 2014, CDC announced that Ebola cases in West Africa could exceed 550,000 by January.
If current trends continue, they say the future number of cases in Liberia and Sierra Leone could exceed 550,000 by January. That estimate is based on reported cases. If under-reporting is taken into account, their calculations suggest that figure is likely to be nearer 1.4 million.
The Ebola outbreak in Nigeria appears to be nearing a possible end due to a rapid response coordinated by Nigeria's Emergency Operations Center with assistance from international partners, including the CDC.
The official end to an Ebola outbreak comes when two of the 21-day incubation periods for Ebola virus have elapsed without any new cases."Although Nigeria isn't completely out of the woods, their extensive response to a single case of Ebola shows that control is possible with rapid, focused interventions," said CDC Director Tom Frieden, "Countries throughout the region as well as Nigeria need to take rapid steps to prepare for possible cases of Ebola in order to prevent outbreaks in their country."
WHO have launched a new $100 million response plan as part of an intensified international, regional and national campaign, to combat the outbreak of Ebola in West Africa:
A discussion panel, led by WHO, concluded that it is ethical to offer unproven interventions with as yet unknown efficacy and adverse effects, as potential treatment or prevention for Ebola.
"The scale of the Ebola outbreak, and the persistent threat it poses, requires WHO and Guinea, Liberia and Sierra Leone to take the response to a new level, and this will require increased resources, in-country medical expertise, regional preparedness and coordination," says Dr Margaret Chan, Director-General of the World Health Organization. "The countries have identified what they need, and WHO is reaching out to the international community to drive the response plan forward."
On the 11th August 2014, WHO assembled a discussion panel to consider and assess the ethical implications for clinical decision-making of the potential use of unregistered interventions.
The panel reached consensus that "it is ethical to offer unproven interventions with as yet unknown efficacy and adverse effects, as potential treatment or prevention. Ethical criteria must guide the provision of such interventions. These include transparency about all aspects of care, informed consent, freedom of choice, confidentiality, respect for the person, preservation of dignity and involvement of the community."
Ebola virus disease (EVD), previous known as Ebola hemorrhagic fever (Ebola HF), is a serious, often fatal condition in humans and nonhuman primates such as monkeys, gorillas and chimpanzees. Ebola is one of several viral hemorrhagic fevers (VHF), caused by infection with a virus of the Filoviridae family, genus Ebolavirus.1-3
Ebola has a case fatality rate of up to 90% and is currently one of the world's most infectious diseases. The infection is transmitted by direct contact with the blood, body fluids and tissues of infected animals or people. Severely ill patients require intensive supportive care.4
Contents of this article:
This Medical News Today information page will give you the essential details about Ebola. You will also see introductions at the end of some sections to any recent developments that have been covered by MNT's news stories. Also look out for links to information about related conditions.
Fast facts on Ebola
Here are some key points about Ebola. More detail and supporting information is in the main article.
- Ebola virus disease (EVD) is a serious, often fatal condition in humans and nonhuman primates.
- Ebola has a fatality rate of up to 90%.
- It is one of the world's most infectious diseases.
- Genus Ebolavirus is one of three members of the Filoviridae family (filovirus).
- It has been hypothesized by researchers that the virus is animal-borne.
- In an outbreak or isolated case among humans, the manner in which the virus is transmitted from the natural reservoir to a human is unclear.
- Ebola tends to spread quickly through families and friends as they are exposed to infectious secretions when caring for an ill individual.
- The time interval from infection with Ebola to the onset of symptoms is 2 to 21 days.
- EVD is often characterized by the abrupt onset of fever, intense weakness, muscle pain, headache and sore throat.
- There is currently no licensed vaccine available for Ebola.
- Several vaccines are being tested, but at this time none are available for clinical use.
What is Ebola?
The first cases of Ebola were reported simultaneously in 1976 in Yambuku and the surrounding area, near the Ebola River in Zaire, which is now the Democratic Republic of the Congo and in Nzara, Sudan. Since then, eruptions or asymptomatic cases of Ebola viruses in humans and animals have surfaced intermittently in the following locations due to outbreaks or laboratory contamination and accidents:5
The first cases of Ebola were reported in 1976 in Yambuku and the surrounding area, near the Ebola River in Zaire, which is now the Democratic Republic of the Congo.
- Zaire (Democratic Republic of the Congo - DRC)
- Sudan (South Sudan)
- Ivory Coast
- South Africa
- Sierra Leone.
Genus Ebolavirus is one of three members of the Filoviridae family (filovirus), along with genus Marburgvirus and genus Cuevavirus. Genus Ebolavirus comprises five distinct subspecies:1,2
- Bundibugyo Ebolavirus (BDBV)
- Zaire Ebolavirus (EBOV)
- Reston Ebolavirus (RESTV)
- Sudan Ebolavirus (SUDV)
- Taï Forest Ebolavirus (TAFV).
BDBV, EBOV, and SUDV have been connected with considerable EVD outbreaks in Africa, however RESTV and TAFV have not.
The RESTV subspecies found in Philippines and the People's Republic of China, can infect humans, but no illness or death in humans from this species has been reported to date.2 Among workers in contact with monkeys or pigs infected with RESTV, several infections have been documented in people who were clinically asymptomatic. Hence, RESTV appears less able to cause disease in humans than other Ebola species.
What causes Ebola?
Ebola is caused by the five viruses detailed above classified in the genus Ebolavirus, family Filoviridae. The natural reservoir of Ebolavirus has not yet been proven, for that reason, how the virus first appears in a human at the onset of an outbreak is unknown.6
It has been hypothesized by researchers that the virus is zoonotic (animal-borne), with the first patient developing the infection through contact with an infected animal.
Ebola is caused by the five viruses above classified in the genus Ebolavirus, family Filoviridae.
The theorized potential natural reservoirs of the Ebola virus are Fruit bats of the Pteropodidae family.2 In Africa, infection has been documented through the handling of the following infected animals found ill or dead or in the rainforest:
- Fruit bats
- Forest antelope
In an outbreak or isolated case among humans, the manner in which the virus is transmitted from the natural reservoir to a human is unclear. Person-to-person transmission is a method by which further infections occur after a human is infected.
Transmission of Ebola between humans can occur in several ways, including through:
- Direct contact through broken skin and mucus membranes with the blood, secretions, organs or other bodily fluids of infected people
- Indirect contact with environments contaminated with such fluids
- Exposure to objects (such as needles) that have been contaminated with infected secretions
- Burial ceremonies in which mourners have direct contact with the body of the deceased person can also play a role in the transmission of Ebola
- Men who have recovered from the disease can still transmit the virus through their semen for up to 7 weeks after recovery from illness
- Health care workers have frequently been infected while treating patients with suspected or confirmed EVD.
Ebola tends to spread quickly through families and friends as they are exposed to infectious secretions when caring for an ill individual. The virus can also spread quickly within health care settings for the same reason, highlighting the importance of wearing appropriate protective equipment, such as masks, gowns and gloves.7 Sterilization and disposal of needles and syringes thoroughly in hospitals is an important factor to prevent virus transmission continuing and amplifying an outbreak.
There is no evidence that Ebola can be spread via insect bites.8
Recent developments on Ebola causes from MNT news
Researchers at the University of Virginia School of Medicine have discovered that the deadly Ebola virus uses a "molecular fist" to punch its way out of vesicles - the secure pockets that cells keep captured viruses and other unwanted agents in until they can be disposed of.
What determines the location and severity of Ebola virus outbreaks? According to Tulane University School of Public Health and Tropical Medicine researcher Daniel Bausch, lead author of "Outbreak of Ebola Virus Disease in Guinea: Where Ecology Meets Economy," a new article in PLOS Neglected Tropical Diseases, the causes are a composite of biological and ecological circumstances superimposed on populations made vulnerable by social and political strife.
The World Health Organization have announced that the Ebola virus in the new outbreak in the Democratic Republic of Congo is not derived from strains circulating in the current outbreak in West Africa.
An international research team has rapidly sequenced 99 Ebola virus genomes collected in the 2014 outbreak. The team, including members from the Broad Institute and Harvard University in the US and the Sierra Leone Ministry of Health and Sanitation, hopes the findings will help multidisciplinary, international efforts to understand and contain the unprecedented epidemic that is growing in West Africa.
Signs and symptoms
The time interval from infection with Ebola to the onset of symptoms is 2 to 21 days, although 8 to 10 days is most common. Signs and symptoms may include:9
EVD is often characterized by the abrupt onset of fever, intense weakness, muscle pain, headache and sore throat.
- Joint and muscle aches
- Stomach pain
- Lack of appetite.
Some patients may experience:
- A rash
- Red eyes
- Sore throat
- Chest pain
- Difficulty breathing
- Difficulty swallowing
- Bleeding inside and outside of the body.
EVD is often characterized by the abrupt onset of fever, intense weakness, muscle pain, headache and sore throat. These signs are usually followed by vomiting, diarrhea, rash, impaired kidney and liver function, and in some severe cases, both internal and external bleeding.
Laboratory outcomes include low white blood cell and platelet counts and elevated liver enzymes.
As long as the patient's blood and secretions contain the virus, they are infectious. Ebola virus was isolated from semen 61 days after onset of illness in a man who was infected in a laboratory.2
Risk of contracting Ebola is low. There is a higher risk of becoming infected when:10
- Traveling to Africa - where most confirmed cases of Ebola have been reported
- Conducting animal research with monkeys imported from Africa or the Philippines
- Providing medical or personal care - protective gear such as surgical masks and gloves should be worn
- Preparing people for burial.
Tests and diagnosis
Before Ebola can be diagnosed, other diseases should be ruled out such as:2
- Typhoid fever
- Relapsing fever
- Other viral hemorrhagic fevers.
If Ebola is suspected, the patient should be isolated, and public health professionals notified. Ebola virus infections can be diagnosed definitively in a laboratory through several types of tests.11
Within a few days after symptoms begin, the virus can be diagnosed with:
- Antigen-capture enzyme-linked immunosorbent assay (ELISA) testing
- IgM ELISA
- Polymerase chain reaction (PCR)
- Virus isolation.
In the more advanced stages of the disease or after recovery, the diagnostic test available is:
- IgM and IgG antibodies.
Retrospectively Ebola can be diagnosed in deceased patients by:
- Immunohistochemistry testing
- Virus isolation.
According to the World Health Organization, samples from patients with Ebola are an extreme biohazard risk. Testing should be conducted under maximum biological containment conditions.
Recent developments on Ebola diagnosis from MNT news
The spread of deadly Ebola in West Africa appears to be increasing and getting out of control, as a leading medical charity warns of over-stretched resources, and concerns are raised that it may spread to other continents.
The Lancet publish a statement from researchers working in Sierra Leone calling for improvements to health care resources, disease surveillance and diagnostic technologies to tackle the ongoing Ebola crisis in West Africa.
Researchers working in the field of synthetic biology are bringing together science, engineering and computing to understand and copy the workings of biological life in new ways to achieve remarkable breakthroughs. Two studies published in Cell show how advances in this field could one day lead to cheap, reliable diagnostics for diseases like Ebola - tests that could be done rapidly in the field using only drops of blood or saliva on strips of paper embedded with synthetic biology circuits.
How is Ebola treated?
Treatment for Ebola is limited to intensive supportive care and often includes:12
- Balancing the patient's fluids and electrolytes
- Maintaining their oxygen status and blood pressure
- Treating a patient for any complicating infections.
Experimental treatments have been tested and proven effective in animal models but as yet have not been used in humans.
Recent developments on Ebola treatment from MNT news
Researchers in the US have identified a natural antiviral protein that stops HIV and certain other deadly viruses like Ebola, Rift Valley Fever and Nipah, from entering host cells.
The so-called miraculous treatment of the two American missionaries struck down by the Ebola virus has been in the headlines for the past week, but where did this drug come from? In a scientific commentary, Dr. Scott Podolsky writes that the inspiration for the drug is rooted in the pioneering research of the late 19th century.
As our knowledge of the molecular structure of Ebola virus increases, so does our chance of preventing and treating the outbreaks of deadly hemorrhagic fever that it causes. Now, a new crystallography study from the US shows how a key Ebola protein - important for virus replication - could be a target for new drugs.
In response to the Ebola outbreak across West Africa, scientists around the world are racing to develop a vaccine against the disease. Now, a study by researchers from the National Institutes of Health reveals the creation of a vaccine that has generated long-term immunity against the Ebola virus in monkeys. The vaccine is now entering phase one clinical trials in humans.
An international group of scientists is to test whether antibodies from the blood and serum of Ebola survivors are safe and can help infected people fight the virus. Trials are due to start in Guinea in a few weeks.
An experimental anti-Ebola vaccine that can be taken in inhaled form is showing promise following animal trials that compared it to injected forms. Results of the pre-clinical study are reported in the journal Molecular Pharmaceutics. It is thought to be the only proof to date that a single, non-injected dose of anti-Ebola vaccine can give long-lasting protection.
A new mouse model has been created to more accurately reflect the human experience of Ebola infection. Researchers hope that the new mouse strain will accelerate research on potential vaccines and treatments for Ebola.
How is Ebola prevented?
There is currently no licensed vaccine available for Ebola. Several vaccines are being tested, but at this time none are available for clinical use.
As it is still unknown how individuals are infected with Ebola, the prevention of the infection presents a challenge. However, there are primary prevention measures that can assist with the challenge, such as:13
- Wearing of protective clothing (such as masks, gloves, gowns and goggles) for health care professionals
- The use of infection-control measures (such as complete equipment sterilization and routine use of disinfectant)
- Isolation of Ebola patients from contact with unprotected persons.
Together with the World Health Organization, CDC has developed a set of guidelines to help prevent and control the spread of Ebola - Infection Control for Viral Hemorrhagic Fevers In the African Health Care Setting.14
Recent developments on Ebola prevention from MNT news
The World Health Organization is urging countries affected by the current Ebola outbreak in West Africa to check exiting travelers for signs consistent with infection by the virus.
The spread of Ebola outbreaks (1976-2015)
View The Spread of Ebola Outbreaks (1976-2015) in a larger map
Written by Hannah Nichols