What is Ebola Virus Disease?
Ebola virus disease (EVD) is a severe, often fatal illness, with a case fatality rate of up to 90%. It is one of the world’s most virulent 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. During an outbreak, those at higher risk of infection are health workers, family members and others in close contact with sick people and deceased patients. Ebola outbreaks can devastate families and communities, but the infection can be controlled through the use of recommended protective measures in clinics and hospitals, at community gatherings, or at home.
What are the symptoms of Ebola Virus Disease?
Symptoms generally include:
- Fever (greater than 38.6°C or 101.5°F)
- Severe headache
- Muscle pain
- Abdominal (stomach) pain
- Lack of appetite
Symptoms may appear anywhere from 2 to 21 days after exposure to ebolavirus, although 8-10 days is most common. EVD is a severe acute viral illness often characterized by the sudden onset of fever, intense weakness, muscle pain, headache and sore throat. This is followed by vomiting, diarrhrea, rash, impaired kidney and liver function, and in some cases, both internal and external bleeding. Laboratory findings include low white blood cell and platelet counts and elevated liver enzymes.
People are infectious as long as their blood and secretions contain the virus. Ebola virus was isolated from semen 61 days after onset of illness in a man who was infected in a laboratory.
The incubation period, that is, the time interval from infection with the virus to onset of symptoms, is 2 to 21 days.
Other diseases that should be ruled out before a diagnosis of EVD can be made include: malaria, typhoid fever, shigellosis, cholera, leptospirosis, plague, rickettsiosis, relapsing fever, meningitis, hepatitis and other viral haemorrhagic fevers.
Ebola virus infections can be diagnosed definitively in a laboratory through several types of tests:
- Antibody-capture enzyme-linked immunosorbent assay (ELISA)
- Antigen detection tests
- Serum neutralization test
- Reverse transcriptase polymerase chain reaction (RT-PCR) assay
- Electron microscopy
- Virus isolation by cell culture.
Some who become sick with Ebola are able to recover. It is not yet fully understood why. However, patients who die usually have not developed a significant immune response to the virus at the time of death.
About Ebola Hemorrhagic Fever
Ebola hemorrhagic fever (Ebola HF) 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 HF 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.
Treatment of Ebola Hemorrhagic Fever
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. No licensed vaccine for EVD is available. Several vaccines are being tested, but none are avialable for clinical use.
2014 Outbreak in West Africa
The 2014 Ebola outbreak is one of the largest Ebola outbreaks in history and the first in West Africa. It is affecting four countries in West Africa: Guinea, Liberia, Nigeria, and Sierra Leone, but does not pose a significant risk to the U.S. public
The CDC is working with other U.S. government agencies, the World Health Organization, and other domestic and international partners in an international response to the current Ebola outbreak in West Africa. CDC has activated its Emergency Operations Center (EOC) to help coordinate technical assistance and control activities with partners. CDC has deployed several teams of public health experts to the West Africa region and plans to send additional public health experts to the affected countries to expand current response activities.
As of August 20, 2014
The Guinean Ministry of Health, the Ministry of Health and Sanitation of Sierra Leone, the Ministry of Health and Social Welfare of Liberia, and the Nigerian Ministry of Health are working with national and international partners to investigate and respond to the outbreak.
- The Guinea Ministry of Health announced 607 suspect and confirmed cases of Ebola virus disease (EVD), including 443 laboratory-confirmed cases, and 406 deaths.
- Affected districts include Conakry, Guéckédou, Macenta, Kissidougou, Dabola, Djingaraye, Télimélé, Boffa, Kouroussa, Dubreka, Fria, Siguiri, Pita, Nzerekore, and Yamou; several are no longer active areas of EVD transmission.
- The Ministry of Health and Social Welfare of Liberia and WHO have reported 1082 suspect and confirmed EVD cases, including 269 laboratory-confirmed, and 624 deaths.
- The Nigerian Ministry of Health and WHO reported 16 suspect and confirmed cases, including 12 laboratory-confirmed, and 5 deaths.
- The Ministry of Health and Sanitation of Sierra Leone and WHO reported a cumulative total of 910 suspect and confirmed cases, including 804 laboratory-confirmed cases, and 392 deaths.
- Cases have been reported from all 12 Sierra Leone districts.
About the virus
- Genetic analysis of the virus indicates that it is closely related (97% identical) to variants of Ebola virus (species Zaire ebolavirus) identified earlier in the Democratic Republic of the Congo and Gabon (Baize et al. 2014).