Nature and Classification
Ebola is a severe viral disease affecting humans and other primates. It is caused by viruses belonging to the genus Orthoebolavirus and the family Filoviridae.
These are enveloped, single-stranded RNA viruses with a characteristic thread-like appearance.
Important ebolaviruses include:
- Ebola virus
- Sudan virus
- Bundibugyo virus
- Taï Forest virus
- Reston virus
- Bombali virus
Not all ebolaviruses are known to cause human disease. Ebola virus, formerly called Zaire ebolavirus, has caused several of the largest and most fatal outbreaks.
The disease was first identified in 1976 during outbreaks in present-day South Sudan and the Democratic Republic of the Congo. It was named after the Ebola River located near one of the affected areas.
Transmission
Ebola is a zoonotic disease, meaning that the virus initially passes from animals to humans. Fruit bats are considered likely natural hosts, although the complete natural transmission cycle is not fully established.
Initial infection may occur through contact with the blood, organs or bodily fluids of infected wild animals such as:
- fruit bats;
- non-human primates;
- forest antelopes;
- porcupines.
Human-to-human transmission occurs through direct contact with:
- blood;
- vomit and diarrhoea;
- saliva and other secretions;
- semen and vaginal fluids;
- organs or tissues;
- contaminated clothing, bedding, needles and medical equipment.
The virus enters the body through broken skin or mucous membranes of the eyes, nose or mouth.
Ebola is not generally transmitted through ordinary airborne spread. An infected person is not considered contagious before symptoms appear.
Healthcare workers and family members face higher risks when infection-control measures are inadequate. Traditional burial practices involving direct contact with the body can also spread the virus.
Symptoms and Disease Progression
The incubation period ranges from 2 to 21 days, with symptoms commonly beginning around 8–10 days after exposure.
Early symptoms include:
- sudden fever;
- severe weakness and fatigue;
- headache;
- muscle pain;
- sore throat;
- loss of appetite.
The illness may later progress to:
- vomiting and severe diarrhoea;
- abdominal pain;
- skin rash;
- impaired kidney and liver function;
- low blood pressure;
- internal or external bleeding;
- shock and multiple-organ failure.
Bleeding is not present in every patient and is generally a feature of severe disease rather than the defining symptom of all cases.
The disease can cause extensive fluid loss, inflammation, damage to blood vessels and disruption of the body’s clotting system. Fatality rates vary according to the virus species, outbreak conditions and availability of medical care.
Diagnosis and Treatment
Early symptoms resemble malaria, typhoid, meningitis and several other infections. Laboratory confirmation is therefore essential.
Diagnostic methods include:
- reverse transcription polymerase chain reaction;
- antigen-detection tests;
- antibody-detection tests;
- virus isolation in specialised high-security laboratories.
Patient samples are highly infectious and must be collected, transported and tested under strict biosafety conditions.
Early supportive treatment significantly improves survival. It includes:
- oral or intravenous fluids;
- correction of electrolyte imbalance;
- maintenance of blood pressure and oxygen levels;
- treatment of secondary infections;
- management of bleeding and organ complications.
Monoclonal-antibody treatments are available for disease caused by Ebola virus. However, approved treatments and vaccines do not provide equal protection against every ebolavirus species.
Recovered patients may continue to carry the virus in certain body fluids, particularly semen, for an extended period. Follow-up care and safe-sex guidance are therefore important.
Prevention and Outbreak Control
Effective outbreak control requires rapid identification and isolation of cases.
Major measures include:
- surveillance and laboratory confirmation;
- isolation and clinical treatment;
- tracing and monitoring of contacts for 21 days;
- use of personal protective equipment;
- safe handling of medical waste;
- disinfection of contaminated materials;
- safe and dignified burials;
- community awareness and cooperation;
- vaccination where an effective vaccine is available.
Ring vaccination may be used during outbreaks caused by Ebola virus. It involves vaccinating the contacts of a confirmed patient and the contacts of those contacts, creating a protective ring around the case.
Mistrust, misinformation, conflict, population movement and weak health systems can make outbreak control more difficult. Public-health measures must therefore involve local communities and respect cultural practices while maintaining infection safety.
Conclusion
Ebola is a highly dangerous zoonotic disease transmitted mainly through direct contact with infected bodily fluids. Although it can cause severe illness and death, early diagnosis, supportive care, appropriate treatment, vaccination and rigorous contact tracing can significantly reduce transmission and mortality.
