Safe handling of Ebola samples: guidance from the CDC

Oct. 19, 2014

As this issue of Medical Laboratory Observer goes to press, there have been no reports of a single case of Ebola hemorrhagic fever contracted in the United States. The only patients who have been treated for Ebola in the U.S. were American healthcare workers who were brought home from Liberia. Dr. Kent Brantly and Nancy Writebol were flown under conditions of extraordinary security to Emory University Hospital in Atlanta, and treated successfully there; Dr. Rick Sacra is being treated in a special isolation unit at Nebraska Medical Center in Omaha; an unidentified fourth American  reportedly is undergoing treatment in Atlanta.

A colorized transmission electron micrograph (TEM) reveals some of the ultrastructural morphology displayed by an Ebola virus virion.

According to news reports some 68 people, all of whom had recently traveled to West Africa, have been evaluated for Ebola at hospital and state labs. It was reported that 58 of the suspected cases were quickly judged to be false alarms. The other ten, reportedly, were forwarded to the Centers for Disease Control and Prevention (CDC) for testing, and eventually Ebola was ruled out in every case.  

From the beginning of the epidemic, the CDC has stressed that the chances of the outbreak spreading beyond West Africa are very small, and the chances of it spreading to the United States are much smaller than that. Nevertheless, the CDC is preparing for any possibility, including that a traveler might become ill with Ebola while in the United States. The CDC has been:

  • enhancing surveillance and laboratory testing capacity in states to detect cases; 
  • developing guidance and tools for health departments to conduct public health investigations;
  • providing recommendations for healthcare infection control and other measures to prevent disease spread; 
  • providing guidance for flight crews, emergency medical units at airports, and Customs and Border Patrol officers about reporting ill travelers to CDC;
  • disseminating up-to-date information to the general public, international travelers, and public health partners. 

The CDC has also issued a Level 3 travel warning to avoid nonessential travel to the nations of Guinea, Liberia, and Sierra Leone.

Currently, the CDC and the Department of Defense have the only U.S. laboratories capable of conducting diagnostic testing—ELISA and more rapid PCR-based molecular testing—to confirm that a patient has Ebola. That is about to change. Additional labs across the United States—part of the Laboratory Response Network (LRN) established by the CDC—will soon have the technology and the go-ahead to conduct Ebola diagnostic testing on acute-phase specimens. The LRN, which became operational in 1999 after being established by a presidential directive, is charged with the task of maintaining an integrated network of state and local public health, federal, military, and international laboratories that can respond to bioterrorism, chemical terrorism, and other public health emergencies.

A CDC disease detective inspects her gear prior to deploying to West Africa for the Ebola outbreak.

These labs have received detailed guidance on the inactivation and safe handling of samples potentially carrying Ebola virus. Once they demonstrate that they can accurately detect or rule out Ebola in a sample, these labs will be capable of rapidly providing presumptive diagnosis for people suspected of having Ebola. The rapid presumptive results will then be definitively confirmed by laboratories at the CDC.

In a document providing “Interim Guidance for Specimen Collection, Transport, Testing, and Submission for Patients with Suspected Infection with Ebola Virus Disease” for laboratories, the CDC provided the following directions for specimen collection and handling: (What follows is excerpted from the CDC document; you can access the full document at

Transporting specimens within the hospital/institution: In compliance with 29 CFR 1910.1030, specimens should be placed in a durable, leak-proof secondary container for transport within a facility. To reduce the risk of breakage or leaks, do not use any pneumatic tube system for transporting suspected EVD specimens.

Recommendations for specimen collection by staff: Any person collecting specimens from a patient with a case of suspected Ebola virus disease should wear gloves, water-resistant gowns, full face shield or goggles, and masks to cover all of nose and mouth. Additional PPE may be required in certain situations.

Recommendations for laboratory testing by staff: Any person testing specimens from a patient with a suspected case of Ebola virus disease should wear gloves, water-resistant gowns, full face shield or goggles, and masks to cover all of nose and mouth, and as an added precaution use a certified class II Biosafety cabinet or Plexiglass splash guard with PPE to protect skin and mucous membranes. All manufacturer-installed safety features for laboratory instruments should be used.

When specimens should be collected for Ebola testing: Ebola virus is detected in blood only after onset of symptoms, most notably fever. It may take up to 3 days post-onset of symptoms for the virus to reach detectable levels. Virus is generally detectable by real-time RT-PCR from 3-10 days post-onset of symptoms. 

Specimens ideally should be taken when a symptomatic patient reports to a healthcare facility and is suspected of having an EVD exposure; however, if the onset of symptoms is < 3 days, a subsequent specimen will be required to completely rule out EVD, if the first specimen tests negative.

Preferred specimens for Ebola testing A minimum volume of 4mL whole blood preserved with EDTA, clot activator, sodium polyanethol sulfonate (SPS), or citrate in plastic collection tubes can be submitted for EVD testing. Do not submit specimens to CDC in glass containers. Do not submit specimens preserved in heparin tubes. Specimens should be stored at 4°C or frozen. Specimens other than blood may be submitted upon consult with the CDC….Standard labeling should be applied for each specimen. The requested test only needs to be identified on the requisition and CDC specimen submission forms.

Storing clinical specimens for Ebola: Specimens should be stored at 4°C or frozen.

Diagnostic testing for Ebola performed at CDC: Several diagnostic tests are available for detection of EVD. Acute infections will be confirmed using a real-time RT-PCR assay (CDC test directory code CDC -10309 Ebola Identification) in a CLIA-accredited laboratory. Virus isolation may also be attempted. Serologic testing for IgM and IgG antibodies will be completed for certain specimens and to monitor the immune response in confirmed EVD patients (#CDC-10310 Ebola Serology).

Lassa fever is also endemic in certain areas of West Africa and may show symptoms similar to early EVD. Diagnostic tests including but not limited to RT-PCR, antigen detection, and IgM serology may be utilized to rule out Lassa fever in EVD-negative patients.

Packaging and shipping clinical specimens to CDC: Specimens collected for EVD testing should be packaged and shipped without attempting to open collection tubes or aliquot specimens…Specimens for shipment should be  packaged following the basic triple packaging system which consists of a primary container (a sealable specimen bag) wrapped with absorbent material, secondary container (watertight, leak-proof), and an outer shipping package. See the CDC site for specific steps to follow in submitting samples.

Ebola presents an evolving clinical, health management, social, and geopolitical challenge, and the responses to that challenge will also need to continuously evolve. With the activation of the Laboratory Response Network, and as the epidemic develops and, eventually, subsides, the CDC’s directives will surely be updated.