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Epidemiologic Risk Factors to Consider when Evaluating a Person for Exposure to Ebola Virus

Updated: May 28, 2015

The following epidemiologic risk factors should be considered when evaluating a person for Ebola virus disease (EVD), classifying contacts, or considering public health actions such as monitoring and movement restrictions based on exposure.

  1. High risk includes any of the following:

In any country

    • Percutaneous (e.g., needle stick) or mucous membrane exposure to blood or body fluids (including but not limited to feces, saliva, sweat, urine, vomit, and semen1) from a person with Ebola who has symptoms
    • Direct contact with a person with Ebola who has symptoms, or the person’s body fluids, while not wearing appropriate personal protective equipment (PPE)
    • Laboratory processing of blood or body fluids from a person with Ebola who has symptoms while not wearing appropriate PPE or without using standard biosafety precautions
    • Providing direct care to a person showing symptoms of Ebola in a household setting

In countries with widespread transmission or cases in urban settings with uncertain control measures

    • Direct contact with a dead body while not wearing appropriate PPE.
  1. Some risk includes any of the following:

In any country

    • Being in close contact2 with a person with Ebola who has symptoms while not wearing appropriate PPE (for example, in households, healthcare facilities, or community settings)

In countries with widespread transmission

    • Direct contact with a person with Ebola who has symptoms, or the person’s body fluids, while wearing appropriate PPE
    • Being in the patient-care area of an Ebola treatment unit
    • Providing any direct patient care in non-Ebola healthcare settings
  1. Low (but not zero) risk includes any of the following:

In any country

    • Brief direct contact (such as shaking hands) with a person in the early stages of Ebola, while not wearing appropriate PPE. Early signs can include fever, fatigue, or headache.
    • Brief proximity with a person with Ebola who has symptoms (such as being in the same room, but not in close contact) while not wearing appropriate PPE
    • Laboratory processing of blood or body fluids from a person with Ebola who has symptoms while wearing appropriate PPE and using standard biosafety precautions
    • Traveling on an airplane with a person with Ebola who has symptoms and having had no identified some or high risk exposures

In countries with widespread transmission, cases in urban settings with uncertain control measures, or former widespread transmission and current, established control measures

    • Having been in one of these countries and having had no known exposures

In any country other than those with widespread transmission

    • Direct contact with a person with Ebola who has symptoms, or the person’s body fluids, while wearing appropriate PPE
    • Being in the patient-care area of an Ebola treatment unit
  1. No identifiable risk includes any of the following:
  • Laboratory processing of Ebola-containing specimens in a Biosafety Level 4 facility
  • Any contact with a person who isn’t showing symptoms of Ebola, even if the person had potential exposure to Ebola virus
  • Contact with a person with Ebola before the person developed symptoms
  • Any potential exposure to Ebola virus that occurred more than 21 days previously
  • Having been in a country with Ebola cases, but without widespread transmission, cases in urban settings with uncertain control measures, or former widespread transmission and now established control measures, and not having had any other exposures
  • Having stayed on or very close to an airplane or ship (for example, to inspect the outside of the ship or plane or to load or unload supplies) during the entire time that the airplane or ship was in a country with widespread transmission or a country with cases in urban settings with uncertain control measures, and having had no direct contact with anyone from the community
  • Having had laboratory-confirmed Ebola and subsequently been determined by public health authorities to no longer be infectious (i.e., Ebola survivors)

[1] Ebola virus can be detected in semen for months after recovery from the disease.  Unprotected contact with the semen of a person who has recently recovered from Ebola may constitute a potential risk for exposure. The period of risk is not yet defined.

[2] Close contact is defined as being within approximately 3 feet (1 meter) of a person with Ebola while the person was symptomatic for a prolonged period of time while not using appropriate PPE.

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