Ebola virus

OVERVIEW

• Ebola virus is an extremely infectious and highly pathogenic virus of primates that causes Ebola virus disease
• the term Ebola haemorrhagic fever is no longer used by WHO as haemorrhage is not a consistent feature of the disease
• the first cases were identified in 1976 in the Congo (near the Ebola River) and in Sudan
• Epidemics occur in Sub-Saharan Africa — 2014 has seen the largest ever outbreak affecting West Africa (over 3000 deaths by September 2014 with a case fatality rate of about 60%)
•  the Zaire strain of Ebola virus had a case fatality rate of 50% to 90%

PATHOGENESIS

Ebola virus

• a filovirus (the Filoviridae family, which also includes the Marburg virus, Lassa Fever, Crimean-Congo fever)
• 5 species: Zaire, Sudan, Reston. Tai Forest, Bundibugyo

Epidemiology

• Incubation period of 2 to 21 days
• Reservoirs: Fruit bats of the Pteropodidae family, with intermittent outbreaks in chimpanzees, gorillas, monkeys, and the forest antelope
• Transmission is by direct exposure to the bodily fluids of an infected person or animal (alive or dead)
  — infected bodily fluids include blood, saliva, urine, CSF, semen, vaginal secretions, vomitus, diarrhea, etc)
  — transmission to and from healthcare workers when inadequate infection control precautions are used
  — unprotected sexual contact with confirmed cases up to 7 weeks after recovery
  — close contact with the bodily fluids of killed animals through hunting or preparation of “bushmeat”
  — transmission by heavily contacted fomites is possible, but there are no reports of airborne transmission
• High risk activities include caring for stricken relatives, traditional burial ceremonies in Africa and healthcare workers (especially in resource poor areas)

CLINICAL FEATURES

History

• may be suspected if within 21 days of symptom onset there was (1) travel or residence in an affected areas, or (2) contact with a known probable or confirmed case
• Stage 1: influenza-like prodrome: fever, myalgia. lethargy, fatigue, prostration, headache, sore throat, conjunctival injection
• Stage 2: multi-system features including gastrointestinal (vomiting, diarrhea), neurological (headaches, confusion), vascular (capillary leak, respiratory distress, hypotension), rash
• Stage 3: after 1 week there may be profuse internal and external bleeding (not universal),  multi-organ failure and death

DIAGNOSIS

Case definition requires the combination of:

• Clinical evidence: a compatible clinical illness as determined by an infectious disease physician, AND
• Epidemiological evidence: history of travel to an endemic/epidemic area within 21 days of illness onset

Or

• Contact with a confirmed case

Or

• Exposure to viral haemorrhagic fever (VHF) infected blood or tissues

Contact the jurisdictional Public Health Reference Laboratory if a case is suspected – testing  is performed in a Physical Containment level 4 laboratory

INVESTIGATIONS

Bedside

• VBG

Laboratory

• FBE, CRP, UEC, glucose, LFTs
• Blood cultures
• Blood PCR
• Throat swabs: microscopy and culture, PCR
• Urine MCS, PCR
• Ebola virus serology (IgG and IgM) are also available for Ebola virus.

Imaging

• CXR (pneumonitis)

NB. Blood tests should be minimised where possible due to the high infection risk

MANAGEMENT

Supportive care

• There is no specific treatment once Ebola virus is contracted (though an experimental drug called ZMapp has been used in the 2014 West African outbreak)
• medical management is purely supportive
• high level supportive care may improve outcomes (e.g. Marburg hemorrhagic fever has  mortality rates in Africa of 70-85%; yet the 1967 outbreak in Germany had mortality rate of 20-25% )

Prevention

• Contact precautions: single room with negative pressure air handling  (or alteast a single room that does not circulate air to other areas)
• Transmission-based precautions  (i.e contact and droplet precautions) when performing aerosol-producing procedures
• Personal protective equipment (PPE) (gloves, gowns, P2 (N95) respirators, eye protection and hand hygiene)
• Quarantine
• no vaccine is available

Notifiable disease

References and Links

Journal articles

• Feldmann H. Ebola – A Growing Threat? N Engl J Med. 2014 May 7. [Epub ahead of print] PubMed PMID: 24805988. [Free Full Text]
• Fowler RA, et al. Caring for Critically Ill Patients with Ebola Virus Disease: Perspectives from West Africa. Am J Respir Crit Care Med 2014;epublished August 28th [Free Full Text]
• Klenk HD. Lessons to be learned from the ebolavirus outbreak in West Africa. Emerging Microbes & Infections 2014;3:e61 [Free Full Text]
• Hampton T. Largest-Ever Outbreak of Ebola Virus Disease Thrusts Experimental Therapies, Vaccines Into Spotlight. JAMA 2014;epublished August 27th [Free Full Text]
• Wolz A. Face to Face with Ebola — An Emergency Care Center in Sierra Leone. New Engl J Med 2014;epublished August 27th [Free Full Text]

FOAM and web resources

• WHO Ebola Updates
• ICMWK — Viral haemorrhagic fever guidelines – just in case! (2014)
• Victorian Ebola Virus Disease Response Plan (pdf)