Ebola virus disease

Ebola virus (EBOV) disease is similar to Marburg virus (MARV) - an RNA virus and a member of the Filoviridae.

The spread of this condition, as with Marburg virus has not yet been fully elucidated. It is known that person to person spread is possible from accidental inoculation with infected blood and tissues; it may be true that spread occurs also by sexual intercourse.

• EBOV and MARV are zoonotic viruses, and outside of outbreaks, do not persist in human populations
  • data suggest fruit bats as the reservoir of EBOV and MARV, and the distribution of both viruses appears to be limited to sub-Saharan Africa (with the exception of Reston ebolavirus (REBOV), identified in the Philippines, and not recognized to be associated with human disease)
  • clusters and outbreaks are primarily the result of person-to-person transmission of these viruses, which occurs through direct contact with the body, bodily fluids (commonly to health care workers), or contaminated clothes or linens of an infected person
  • the level of viremia, and thus presumptively the risk of transmission, corresponds with disease severity, with highest concentrations of the virus during later stages of disease

After an incubation period of two to twenty one days there is vomiting and diarrhoea. There is a characteristic morbilliform rash between the third and eighth days, and there may be an alteration in the mental state.

• EBOV is characterized by the sudden onset of fever and malaise, accompanied by other nonspecific signs and symptoms such as myalgia, headache, vomiting, and diarrhea
• among EBOV patients, 30%-50% experience haemorrhagic symptoms (2)
  • in severe and fatal forms, multiorgan dysfunction, including hepatic damage, renal failure, and central nervous system involvement occur, leading to shock and death
  • the first two Ebolavirus species were initially recognized in 1976 during simultaneous outbreaks in Sudan (Sudan ebolavirus) and Zaïre (now Democratic Republic of the Congo) (Zaïre ebolavirus). Since 1976, there have been more than 20 EBOV outbreaks across Central Africa, with the majority caused by Ebola virus (species Zaïre ebolavirus), which historically has demonstrated the highest case-fatality rate (up to 90%) (3)

Treatment with serum from convalescent patients, which contain a high level of neutralising antibody, a method used in the treatment of Argentine haemorrhagic fever is as yet of unproven value.

Actions in the event of a possible case

• if Ebola (or another viral haemorrhagic fever) is considered likely, the patient should be isolated (in a side room if possible), with appropriate infection control measures while a detailed risk assessment is carried out. The Advisory Committee on Dangerous Pathogens (ACDP) risk assessment guidance document and algorithm should be used and is available here: https://www.gov.uk/government/publications/viral-haemorrhagic-feveralgorithm- and-guidance-on-management-of-patients

Reference:

• Francesconi P, Yoti Z, Declich S, Onek PA, Fabiani M, et al. Ebola hemorrhagic fever transmission and risk factors of contacts, Uganda. Emerg Infect Dis. 2003;9:1430-1437
• Médecins Sans Frontières. Filovirus haemorrhagic fever guideline. Barcelona, Spain: Médecins Sans Frontières; 2008:39-48.
• World Health Organization. Ebola viral disease: fact sheet. Geneva, Switzerland: World Health Organization; 2014. Available at http://www.who.int/mediacentre/factsheets/fs103/en