The 2014 Ebola outbreak is the largest in history, primarily affecting Guinea, northern Liberia, and Sierra Leone. The Centers for Disease Control and Prevention (CDC) estimates that the epidemic has caused more than 11,000 deaths, with almost all those deaths occurring in countries in West Africa. In the US, reports indicate that there have been two imported cases, including one death, and two locally acquired cases in healthcare workers.
A small number of cases were reported in Nigeria, Mali and Senegal, with health authorities able to contain these cases and prevent further spread.
Medical News Today examines the effects of Ebola on the human body and the current concerns people may have about the virus.
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
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.
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).
- Ebola is considered a zoonotic virus, meaning that it originated in non-human animals and then spread to humans.
- In an outbreak or isolated case among humans, it is unclear as to how the virus is transmitted from non-human animals to humans.
- 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, although several are in development
- One vaccine, called Ebola ca Suffit, was found to be 100% effective in a trial involving 4,000 people in Guinea.
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)
- United Kingdom
- 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 has caused illness and death in non-human primates, but not in humans.2 Several infections have been documented among people who work with monkeys or pigs infected with RESTV; however, those people infected with RESTV remained clinically asymptomatic. All of the other four viruses have caused disease in humans.
What causes Ebola?
Ebola is caused by the five viruses detailed above classified in the genus Ebolavirus, family Filoviridae. Ebola is considered a zoonosis, meaning that the virus is present in animals and is transmitted to humans. How this transmission occurs at the onset of an outbreak in humans is unknown. The natural reservoir of Ebolavirus also remains unknown, although bats are considered the most likely hosts.6
Ebola is caused by the five viruses above classified in the genus Ebolavirus, family Filoviridae.
Specifically, fruit bats of the Pteropodidae family are suspected to play a key role in maintaining a viral reservoir and transmitting the virus to humans.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
Person-to-person transmission occurs after someone infected with Ebolavirus becomes symptomatic. As it can take between 2 and 21 days for symptoms to arise, a person with Ebola may have had contact with hundreds of people, which is why an outbreak can be hard to control and may spread rapidly.
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
- Exposure to semen of people with Ebola or who have recovered from the disease (the virus can still be transmitted through semen for up to 7 weeks after recovery from illness)
- Contact with patients with suspected or confirmed EVD (health care workers have frequently been infected while treating patients).
Ebola tends to spread quickly through families and among 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 Thorough sterilization and proper disposal of needles and syringes in hospitals is important in preventing further infection and halting the spread of an outbreak an outbreak.
There is no evidence that Ebola can be spread via insect bites.8
Recent developments on Ebola causes from MNT news
A study, published in EMBO Molecular Medicine, suggests the outbreak of the Ebola virus disease occurring in West Africa may have originated from contact between humans and virus-infected bats. The insectivorous free-tailed bats in particular have been identified as plausible reservoir hosts.
After testing swabs and tissue samples from the bodies of deceased Ebola-infected monkeys, scientists determined the virus can stay alive for up to 7 days in a dead victim. They also found that non-infectious viral genetic material can remain for up to 70 days after death. The researchers report their findings in the journal Emerging Infectious Diseases.
New research finds that Ebola can survive in detectable concentrations in wastewater for 8 days - a finding that has implications for the disposal of contaminated liquid waste during epidemics and outbreaks.
A new study suggests that the Ebola virus is still detectable in semen samples from male survivors for at least 9 months after onset of symptoms.
On the next page, we look at symptoms of Ebola, the risk factors and how Ebola is diagnosed. On the final page, we discuss treatments for Ebola, methods of prevention and the spread of Ebola outbreaks.