When an individual with symptoms compatible with Ebola virus disease (EVD) is identified, a sample (whole blood and/or serum) must be taken for etiological diagnosis (see algorithm for management of samples).

An Ebola case is considered confirmed only when the sample from the suspected case tests positive in the laboratory. Since it can take several days for the results to be returned, patient treatment should be empirically started pending definitive confirmation.

The virus can be detected only in patients who have already developed symptoms; as a result, laboratory confirmation is not possible during the incubation period.

In the case of a dead patient with a clinical and epidemiological history compatible with EVD, taking an oral swab is suggested. In these situations, an autopsy is contraindicated.

Biosafety conditions for laboratory diagnosis
The Ebola virus is classified as a Risk Group 4 pathogen; therefore, the viable virus requires handling (viral isolation) in a laboratory with an equivalent containment level (Biosafety Level 4—BSL-4).
Although preliminary detection can be carried out using molecular techniques (PCR) as soon as the sample is inactivated in a BSL-3 containment laboratory, the first cases in a country or territory should be confirmed at a WHO collaborating center (WHO CC——see below). Countries that do not have BSL-4 or BSL-3 laboratories must ensure that the sample is shipped (in accordance with IATA regulations for Category A substances) to a WHO collaborating center.

Rapid testing is discouraged

Due to its low specificity and sensitivity, the use of the rapid testing is not indicated for confirming or for discarding cases; as such, its use is discouraged.

Algorithm for the sample flow of patients with symptoms compatible with EVD (2014-sample-management- algorithm)

algorithm-sample-flow

Sample selection

Viral detection is possible only in symptomatic patients. Samples should not be taken from healthy contacts.

After the onset of symptoms, viremia peaks around day 6 and may be detectable until (approximately) day 15. However, samples collected during days 1-2 after symptom onset may still be negative in infected individuals. For this reason, a second sample should be taken at least 48 hours later to increase the likelihood of detection.

Two results of RT-PCR testing, at least 48 hours apart, are required to discharge an asymptomatic patient from hospital or to discard a suspected case with negative results.

A whole blood sample is recommended for virological diagnosis (5 ml, preferably in a plastic tube with EDTA); however, serum or plasma can also be used.

Laboratory results should be reported to PAHO/WHO as soon as possible and also reported in accordance with the requirements and time frame established by the International Health Regulations (IHR).

Sample collection

Samples must be collected only by trained personnel using all appropriate personal protection equipment (PPE).

Samples must be taken:

  • by trained health workers,
  • with the greatest attention to biosafety measures,
  • and with additional protection equipment: gloves, masks, goggles (preferably with anti-fog visor), and waterproof apron (preferably disposable).

Storage of samples

Samples may be refrigerated at 2-8 ? for up to a week. However, the shipment should be sent to the reference laboratory during the first 48 hours after collection. Biological samples should not be stored under BSL-2 conditions longer than is necessary for shipment.

Shipment of samples

According to the algorithm, samples must be sent to the country's National Reference Laboratory in triple packaging and in compliance with all relevant biosafety measures.

Shipments by air and to the WHO Collaborating Center must be in strict compliance with IATA recommendations for the shipping of Category A infectious substances:

  • triple packaging (P620 packaging instructions)
  • valid shipper's certificate
  • Dangerous Goods Declaration (DGD)
  • air waybill

The cold chain for samples should also be guaranteed. If dry ice is used, it should be contained in a correctly labeled P954 (polystyrene foam) cooler.

Before taking and sending samples, the WHO collaborating center should be contacted through the PAHO Regional Office. The centers will not receive samples without prior authorization.
When shipping samples to the collaborating center, it is important to ensure that a carrier is available (courier or civil airline).

Samples sent to the WHO collaborating center should not be inactivated. Only in special circumstances where it is impossible to ship Category A infectious substances (no available carrier), will shipment of an inactivated sample (category B or exempt) be considered, after consultation with the collaborating center and the PAHO regional office.

WHO has an agreement with World Courier (Switzerland) to provide shipping services. Thanks to this agreement, the cost of using the courier service will be covered by WHO and not by the country/laboratory of origin.

Laboratories in the Region of the Americas that can receive samples for confirmation of EVD are the WHO collaborating centers at the United States Centers for Disease Control and Prevention (CDC) and the National Microbiology Laboratory of Canada.

International shipping of diagnostic specimens of EVD to the Centers for Disease Control and Prevention (CDC), Atlanta, GA, USA

International shipping of diagnostic specimens of EVD to the Public Health Agency of Canada, Winnipeg, Manitoba, Canada

Questions and Answers

pdf Questions and Answers for the Laboratory—Ebola Virus Disease (EVD)

Links:

Guidelines and Technical Documents on Laboratory