Ebola

Ebola virus disease (EVD), formerly known as Ebola haemorrhagic fever, is a severe, often fatal illness in humans. EVD outbreaks have a case fatality rate of up to 90%. EVD outbreaks occur primarily in remote villages in Central and West Africa, near tropical rain forests. 

Orgin

Ebola first appeared in 1976 in 2 simultaneous outbreaks, in Nzara, Sudan, and in Yambuku, Democratic Republic of Congo. The latter was in a village situated near the Ebola River, from which the disease takes its name.

Types of Ebola

Genus Ebolavirus is 1 of 3 members of the Filoviridae family (filovirus), along with genus Marburgvirus and genus Cuevavirus. Genus Ebolavirus comprises 5 distinct species:

·  Bundibugyo ebolavirus (BDBV)

·  Zaire ebolavirus (EBOV)

·  Reston ebolavirus (RESTV)

·  Sudan ebolavirus (SUDV)

·  Tai Forest ebolavirus (TAFV)

Transmission of Ebola

Ebola is introduced into the human population through close contact with the blood, secretions, organs or other bodily fluids of infected animals. In Africa, infection has been documented through the handling of infected chimpanzees, gorillas, fruit bats, monkeys, forest antelope and porcupines found ill or dead or in the rain forest. Fruit bats are considered to be the natural host of the Ebola virus.

Ebola then spreads in the community through human-to-human transmission, with infection resulting from direct contact (through broken skin or mucous membranes) with the blood, secretions, organs or other bodily fluids of infected people, and indirect contact with environments contaminated with such fluids.

Signs and Symptoms

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, diarrhoea, 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.

Diagnosis

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.

·  Samples from patients are an extreme bio-hazard risk; testing should be conducted under maximum biological containment conditions.

Vaccine and Treatment

No licensed vaccine for EVD is available. Several vaccines are being tested, but none are available for clinical use.

Severely ill patients require intensive supportive care. Patients are frequently dehydrated and require oral rehydration with solutions containing electrolytes or intravenous fluids.

No specific treatment is available. New drug therapies are being evaluated.

Ebola virus in animals

Although non-human primates have been a source of infection for humans, they are not thought to be the reservoir but rather an accidental host like human beings. Since 1994, Ebola outbreaks from the EBOV and TAFV species have been observed in chimpanzees and gorillas.

Prevention and control

Reducing the risk of Ebola infection in people. In the absence of effective treatment and a human vaccine, raising awareness of the risk factors for Ebola infection and the protective measures individuals can take is the only way to reduce human infection and death.

In Africa, during EVD outbreaks, educational public health messages for risk reduction should focus on several factors:

The first step was reducing the risk of wildlife-to-human transmission from contact with infected fruit bats or monkeys/apes and the consumption of their raw meat. The second was reducing the risk of human-to-human transmission in the community arising from direct or close contact with infected patients, particularly with their bodily fluids.

Controlling infection in health-care settings

Human-to-human transmission of the Ebola virus is primarily associated with direct or indirect contact with blood and body fluids. Transmission to health-care workers has been reported when appropriate infection control measures have not been observed.

WHO response

WHO provides expertise and documentation to support disease investigation and control. Recommendations for infection control while providing care to patients with suspected or confirmed Ebola haemorrhagic fever are provided in: Interim infection control recommendations for care of patients with suspected or confirmed Filovirus (Ebola, Marburg) haemorrhagic fever, March 2008. This document is currently being updated.

WHO has created an aide–memoire on standard precautions in health care (currently being updated). Standard precautions are meant to reduce the risk of transmission of blood-borne and other pathogens. If universally applied, the precautions would help prevent most transmission through exposure to blood and body fluids.