Unifying Concepts

Case Definition for Ebola Virus Disease (EVD)

Early recognition is critical for infection control. Healthcare providers should be alert for and evaluate any patients suspected of having EVD.

Person Under Investigation (PUI)
A person who has both consistent symptoms and risk factors as follows:
1) Clinical criteria, which includes fever of greater than 38.6 degrees Celsius or 101.5 degrees Fahrenheit, and additional symptoms such as severe headache, muscle pain, vomiting, diarrhea, abdominal pain, or unexplained hemorrhage;
2) Epidemiologic risk factors within the past 21 days before the onset of symptoms, such as contact with blood or other body fluids or human remains of a patient known to have or suspected to have EVD; residence in—or travel to—an area where EVD transmission is active*; or direct handling of bats, rodents, or primates from disease-endemic areas.

Probable Case
A PUI who is a contact of an EVD case with either a high or low risk exposure (see below).
Confirmed Case
A case with laboratory confirmed diagnostic evidence of ebola virus infection.

Contacts of an EVD Case
Contacts of an EVD case have different levels of exposure risk, as follows:

High risk exposures
A high risk exposure includes any of the following:

  • Percutaneous, e.g. the needle stick, or mucous membrane exposure to body fluids of EVD patient
  • Direct care or exposure to body fluids of an EVD patient without appropriate personal protective equipment (PPE)
  • Laboratory worker processing body fluids of confirmed EVD patients without appropriate PPE or standard biosafety precautions
  • Participation in funeral rites which include direct exposure to human remains in the geographic area where outbreak is occurring without appropriate PPE

Low risk exposures
A low risk exposure includes any of the following

  • Household member or other casual contact* with an EVD patient
  • Providing patient care or casual contact* without high-risk exposure with EVD patients in health care facilities in EVD outbreak affected countries

No known exposure
Persons with no known exposure were present in an EVD outbreak affected country in the past 21 days with no low risk or high risk exposures.

* Casual contact is defined as a) being within approximately 3 feet (1 meter) or within the room or care area for a prolonged period of time (e.g., healthcare personnel, household members) while not wearing recommended personal protective equipment (i.e., droplet and contact precautions); or b) having direct brief contact (e.g., shaking hands) with an EVD case while not wearing recommended personal protective equipment (i.e., droplet and contact precautions). At this time, brief interactions, such as walking by a person or moving through a hospital, do not constitute casual contact.



  1. Centers for Disease Control and Prevention. Case Definition for Ebola Virus Disease (EVD). [Web]
  2. Gatherer D. The 2014 Ebola virus disease outbreak in West Africa. J Gen Virol. 2014 Aug;95(Pt 8):1619-1624. [Medline]
  3. Feldmann H, Geisbert TW. Ebola haemorrhagic fever. Lancet. 2011 Mar 5;377(9768):849-62. [Medline]


Created Aug 12, 2014.

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