Ebola Virus Disease (EVD) is one of numerous Viral Hemorrhagic Fevers. It is a severe, often fatal disease in humans and nonhuman primates (such as monkeys, gorillas, and chimpanzees).
Ebola is caused by infection with a virus of the family Filoviridae, genus Ebolavirus. When infection occurs, symptoms usually begin abruptly. The first Ebolavirus species was discovered in 1976 in what is now the Democratic Republic of the Congo near the Ebola River. Since then, outbreaks have appeared sporadically.
There are five identified subspecies of Ebolavirus. Four of the five have caused disease in humans: Ebola virus (Zaire ebolavirus); Sudan virus (Sudan ebolavirus); Taï Forest virus (Taï Forest ebolavirus, formerly Côte d’Ivoire ebolavirus); and Bundibugyo virus (Bundibugyo ebolavirus). The fifth, Reston virus (Reston ebolavirus), has caused disease in nonhuman primates, but not in humans.
The natural reservoir host of ebolaviruses remains unknown. However, on the basis of available evidence and the nature of similar viruses, researchers believe that the virus is zoonotic (animal-borne) with bats being the most likely reservoir. Four of the five subtypes occur in an animal host native to Africa.
A host of similar species is probably associated with Reston virus, which was isolated from infected cynomolgous monkeys imported to the United States and Italy from the Philippines. Several workers in the Philippines and in US holding facility outbreaks became infected with the virus, but did not become ill.
SIGNS & SYMPTOMS:
Symptoms of Ebola typically include
•Fever (greater than 38.6°C or 101.5°F)
•Abdominal (stomach) pain
Symptoms may appear anywhere from 2 to 21 days after exposure to ebolavirus, although 8-10 days is most common.
Some who become sick with Ebola are able to recover. We do not yet fully understand why. However, patients who die usually have not developed a significant immune response to the virus at the time of death.
No specific vaccine or medicine (e.g., antiviral drug) has been proven to be effective against Ebola.
Symptoms of Ebola are treated as they appear. The following basic interventions, when used early, can increase the chances of survival.
•Providing intravenous fluids and balancing electrolytes (body salts)
•Maintaining oxygen status and blood pressure
•Treating other infections if they occur
Timely treatment of Ebola HF is important but challenging because the disease is difficult to diagnose clinically in the early stages of infection. Because early symptoms, such as headache and fever, are nonspecific to ebolaviruses, cases of Ebola HF may be initially misdiagnosed.
However, if a person has the early symptoms of Ebola HF and there is reason to believe that Ebola HF should be considered, the patient should be isolated and public health professionals notified. Supportive therapy can continue with proper protective clothing until samples from the patient are tested to confirm infection.
Experimental treatments have been tested and proven effective in animal models but have not yet been used in humans.
Because the natural reservoir of ebolaviruses has not yet been proven, the manner in which the virus first appears in a human at the start of an outbreak is unknown. However, researchers have hypothesized that the first patient becomes infected through contact with an infected animal.
When an infection does occur in humans, the virus can be spread in several ways to others. The virus is spread through direct contact (through broken skin or mucous membranes) with
•a sick person’s blood or body fluids (urine, saliva, feces, vomit, and semen)
•objects (such as needles) that have been contaminated with infected body fluids
Healthcare workers and the family and friends in close contact with Ebola patients are at the highest risk of getting sick because they may come in contact with infected blood or body fluids.
During outbreaks of Ebola HF, the disease can spread quickly within healthcare settings (such as a clinic or hospital). Exposure to ebolaviruses can occur in healthcare settings where hospital staff are not wearing appropriate protective equipment, such as masks, gowns, and gloves.
Proper cleaning and disposal of instruments, such as needles and syringes, is also important. If instruments are not disposable, they must be sterilized before being used again. Without adequate sterilization of the instruments, virus transmission can continue and amplify an outbreak.
Diagnosing Ebola HF in an individual who has been infected for only a few days is difficult, because the early symptoms, such as red eyes and a skin rash, are nonspecific to ebolavirus infection and are seen often in patients with more commonly occurring diseases.
However, if a person has the early symptoms of Ebola HF and there is reason to believe that Ebola HF should be considered, the patient should be isolated and public health professionals notified. Samples from the patient can then be collected and tested to confirm infection.
Laboratory tests used in diagnosis include:
Because we still do not know exactly how people are infected with Ebola, few primary prevention measures have been established and no vaccine exists.
When cases of the disease do appear, risk of transmission is increased within healthcare settings. Therefore, healthcare workers must be able to recognize a case of Ebola and be ready to use practical viral hemorrhagic fever isolation precautions or barrier nursing techniques.
They should also have the capability to request diagnostic tests or prepare samples for shipping and testing elsewhere.
Barrier nursing techniques include:
wearing of protective clothing (such as masks, gloves, gowns, and goggles)
using infection-control measures (such as complete equipment sterilization and routine use of disinfectant)
isolating patients with Ebola from contact with unprotected persons.
The aim of all of these techniques is to avoid contact with the blood or secretions of an infected patient. If a patient with Ebola dies, direct contact with the body of the deceased patient should be avoided.
CDC, in conjunction with the World Health Organization, has developed a set of guidelines to help prevent and control the spread of Ebola.
Entitled Infection Control for Viral Haemorrhagic Fevers in the African Health Care Setting, the manual describes how to
recognize cases of viral hemorrhagic fever (such as Ebola)
prevent further transmission in healthcare setting by using locally available materials and minimal financial resources.
If you must travel to an area with known Ebola cases, make sure to do the following:
Practice careful hygiene. Avoid contact with blood and body fluids.
Do not handle items that may have come in contact with an infected person’s blood or body fluids.
Avoid funeral or burial rituals that require handling the body of someone who has died from Ebola.
Avoid contact with bats and nonhuman primates or blood, fluids, and raw meat prepared from these animals.
Avoid hospitals where Ebola patients are being treated. The U.S. embassy or consulate is often able to provide advice on facilities.
After you return, monitor your health for 21 days and seek medical care immediately if you develop symptoms of Ebola.