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Epidemiology of Infectious Diseases: Ebola

Causal agent
Ebolavirus (Filoviridae family).

Ebola haemorrhagic fever (EHF) is a febrile haemorrhagic illness of which there are four distinct subtypes: Zaire, Sudan, Cote d'Ivoire and Reston. Zaire, Sudan and Cote d'Ivoire cause illness in humans.

Common clinical features
Sudden onset of fever, malaise, myalgia, diarrhoea, hypotension and shock, vomiting, rash, impaired kidney and liver function and in some cases internal and external bleeding.

Case fatality rates are between 50-90%.


  • Ebola was first identified in 1976 in Sudan and the Democratic Republic of Congo following large outbreaks.
  • Confirmed cases have been reported in the Democratic Republic of Congo (formerly Zaire), Gabon, Sudan, The Ivory Coast and Uganda, Cote d' Ivoire and South Africa.  Most cases have occurred in DRC, Sudan and Uganda.
  • Approximately 1,850 cases with over 1,200 deaths have been documented since the Ebola virus was discovered.

Unknown - possibly primate.
Appears to possibly originate from the rain forests in West and Central Africa and in the Western Pacific.

Mode of transmission

  • Person to person via contact with bodily secretions, organs and blood of infected individuals.
  • The handling of infected (dead and alive) chimpanzees, gorillas and forest antelopes has been documented.
  • Direct contact with the body of a deceased person infected with the virus.
  • Nosocomial transmission occurs frequently during outbreaks.

Incubation period
2-21 days.

Period of Communicability
During acute illness and may be excreted in semen for 2-3 months.
There is no carrier state.

No effective treatment is available. Severe cases require intensive supportive care.

Prevention and control
There is no vaccine against ebola haemorrhagic fever.
Strict isolation of cases and strict barrier nursing techniques implemented. 


  1. World Health Organisation, Ebola Haemorrhagic Fever Fact Sheet No. 103, 2004.

© CM Kirwan 2006