Ebola Virus Disease

Basics

Description

  • Ebola virus disease (EVD) is a zoonotic illness that affects multiple organ systems and has high mortality.
  • Previously called Ebola hemorrhagic fever (EHF) but renamed due to the inconsistent hemorrhage presentation.
  • Prior to 2014, EVD was known for causing localized but deadly outbreaks, usually in remote areas in Central Africa. From 2014 to 2016, there was an EVD outbreak in West Africa caused by the Zaire strain that infected >29,000 people and led to 11,315 deaths. Although the outbreak predominantly affected the West African countries of Guinea, Liberia, and Sierra Leone, cases were identified and treated in 12 other countries, including the United States.
  • Increased globalization, with increasing numbers of people traveling across country borders, supports the importance of continued vigilance

Epidemiology

  • Endemic in Central, Western, and Eastern Africa
  • Although it can infect animals and be further transmitted to humans, most transmission in outbreaks is human-to-human through contact with bodily fluids including blood, saliva, sperm, vomit, feces, vaginal secretions, and breast milk.
  • Neonates are at high risk for vertical transmission in-utero and peripartum.
  • Incubation period of 2 to 21 days, average of 8 to 10 days from exposure to first symptoms
  • Infectivity increases as illness progresses.
  • Subclinical infection indicated by seroprevalence studies, although uncommon
  • Ebola virus is known to remain in certain sanctuary sites including CSF, intraocular fluid, breast milk, vaginal secretions, and semen.
  • No significant difference between incidence in males and female overall

Risk Factors

  • Contact with a person with EVD or their bodily fluids in last 21 days
  • Risk is often stratified by
    • Duration of contact
    • Type of contact
    • Point of illness at which contact occurs
  • Highest risk are those who have direct contact with symptomatic patient or their bodily fluids while not wearing personal protective equipment (PPE).
  • Risk increases as illness progresses and is high for those who have direct contact with a dead body.
  • Risk of transmission is less for those who only have close contact (within 3 feet) but not direct contact with a person or bodily fluids of a person with EVD while not wearing PPE.
  • Wearing appropriate PPE with adherence to donning and doffing practices decreases risk considerably.

General Prevention

ALERT
If EVD is suspected, the patient should be isolated in a separate room with private bathroom. Notify local or state public health officials to ensure appropriate protocols are followed to minimize transmission.
  • Standard, droplet and contact precautions to be employed along with the following PPE:
    • Two sets of gloves
    • N95 mask with face shield or goggles
    • Hood with neck and shoulder coverage
    • Boot covers
  • Safe burial practices, including not touching corpses
  • Not handling or eating animals that have been sick
  • Vaccine (rVSV-ZEBOV) has shown promising results in safety and immunogenicity efficacy.

Pathophysiology

  • Ebola virus enters the body through direct inoculation with needles, through mucous membranes, or through areas in the skin with a loss of integrity.
  • Ebola virus affects multiple systems by infecting monocytes, macrophages, and dendritic cells.
  • Inhibition of type 1 interferon response and induction of inflammatory mediators and cytokines (which can vary between children and adults) triggering systemic inflammatory response and immune dysregulation

Etiology

  • Ebola is a zoonotic disease with an unknown reservoir.
  • The Ebola virus is of the Filoviridae family and has five different strains including Zaire ebolavirus, Sudan ebolavirus, Bundibugyo ebolavirus, Tai Forest ebolavirus, and Reston ebolavirus (which have not caused disease in humans to date).
  • The Zaire strain was the first identified in 1976 and has the highest mortality.

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