As the West African Ebola epidemic continues unabated, countries around the world must prepare for the possibility that an infected traveler might arrive unannounced on their shores. Having a working and deployed public health system – and a criteria for identifying infected cases and their potential contacts – greatly limits the potential for any major outbreaks in developed countries.
The CDC has already released, and updated, their Interim Ebola Case Definitions, as has Canada (National Case Definition: Ebola Virus Disease (EVD)). Both are works in progress and are subject to revision as more is learned.
Today the ECDC has offered their interpretation (see below). And while all three of these case definitions involve many of the same criteria, there are some interesting differences between CDC & ECDC assessments, particularly in what constitutes a `High Risk’ exposure.
As you can see, the ECDC’s list of High Risk exposures is longer, and more encompassing, than is the CDC’s. Unlike the CDC, the ECDC does not elucidate what constitutes `Low Risk’ exposures.
The CDC considers the following scenarios to present a `Low Risk’ of infection.
A low risk exposure includes any of the following
- Household contact with an EVD patient
- Other close contact with EVD patients in health care facilities or community settings. Close contact is defined as
- being within approximately 3 feet (1 meter) of an EVD patient or within the patient’s room or care area for a prolonged period of time (e.g., health care personnel, household members) while not wearing recommended personal protective equipment (i.e., standard, droplet, and contact precautions; see Infection Prevention and Control Recommendations)
- having direct brief contact (e.g., shaking hands) with an EVD patient while not wearing recommended personal protective equipment.
Brief interactions, such as walking by a person or moving through a hospital, do not constitute close contact
With the added proviso that the suspected or confirmed Ebola patient in question is `coughing, vomiting, bleeding, or who had diarrhoea’ - being within 1 meter of an EVD patient is considered to have a High Risk of exposure by the ECDC; essentially recognizing the risks of droplet transmission of the virus.
The potential of droplet transmission of Ebola is something we’ve discussed before, and was well addressed by Dr. Ian Mackay et al. in VDU Blog: Droplets vs Airborne - Demystifying Ebola Transmission.
While one can debate the `reasonableness’ of either criteria (particularly given the different populations and geographic regions involved), the differences between them – and between the various PPE standards we’ve also seen used for or recommended for use with Ebola – risk creating an environment of confusion and distrust among both the public, and healthcare workers.
Here is the ECDC’s release in its entirety:
10 Sep 2014
A case definition for reporting cases of Ebola virus disease in the EU has been released by ECDC. The definition aims to classify cases for epidemiological reporting and not to guide investigation or clinical management of cases.
Although developed in response to the outbreak of Ebola virus disease currently affecting West Africa, the case definition is broad enough to apply to any case of EVD.
Only confirmed cases are to be reported at the European level, although the newly published case definition does include a 'probable case' definition.
Algorithms for laboratory diagnosis of EVD and for the initial assessment and management of patients have also been released. To offer further support to healthcare professionals possibly faced with a situation where the management of patients suffering from EVD becomes necessary, the algorithms are accompanied by a directory of guidance from national institutes and other public health bodies. These guidance documents provide more detailed steps for the management of any EVD patient.
By releasing the case definition and related algorithms, ECDC works to support EU Member States in their preparedness for a quick and effective response to any situation that may potentially involve an EVD case.
Read more:EVD Case definition
Algorithm for laboratory diagnosis of EVD
Algorithm for initial assessment and management of patients for EVD
Directory of guidance on EVD patient management
Ebola and Marburg fevers health topic
Rapid Risk Assessment – EVD in West Africa (fourth update, 3 September 2014)
The classification of cases under this definition relies on clinical, epidemiological, laboratory and high-risk exposure criteria, allowing the identification of persons required to be investigated for EVD and the differentiation of probable and confirmed cases for reporting. The definition aims to classify cases for epidemiological reporting.
Any person currently presenting or having presented before death:
- Fever ≥38.6°C
AND any of the following:
- Severe headache
- Vomiting, diarrhoea, abdominal pain
- Unexplained haemorrhagic manifestations in various forms
- Multi-organ failure
OR a person who died suddenly and inexplicably
Any of the following:
- Detection of Ebola virus nucleic acid in a clinical specimen and confirmation by sequencing or a second assay on different genomic targets.
- Isolation of Ebola virus from a clinical specimen.
In the 21 days before the onset of symptoms:
- having been in an affected area;
- having had contact with a probable or confirmed EVD case.
High-risk exposure criteria
Any of the following:
- close face-to-face contact (e.g. within one metre) without appropriate personal protective equipment (including eye protection) with a probable or confirmed case who was coughing, vomiting, bleeding, or who had diarrhoea; or had unprotected sexual contact with a case up to three months after recovery;
- direct contact with any material soiled by bodily fluids from a probable or confirmed case;
- percutaneous injury (e.g. with needle) or mucosal exposure to bodily fluids, tissues or laboratory specimens of a probable or confirmed case;
- participation in funeral rites with direct exposure to human remains in or from an affected area without appropriate personal protective equipment;
- direct contact with bats, rodents, primates, living or dead, in or from affected areas, or bushmeat.
Person under investigation
- meeting the clinical and the epidemiological criteria;
- with high-risk exposure and any of the listed symptoms, including fever of any grade.
Case classification for reporting at EU level
Only confirmed cases are to be reported at the European level using the EWRS. The 'probable case' classification is provided for information only.
- Not Applicable.
- A person meeting the clinical and high-risk exposure criteria.
- A person meeting the laboratory criteria.