The CDC recommends a triple packaging system: a sealed bag containing the specimen vial should be wrapped in absorbent material, placed in a watertight and leakproof second container, and then placed in a rigid, outer shipping package. Each sample and each level of packaging must be well-labeled.
“Everyone who handles that package has to sign off,” said Dr. Aileen Marty, a professor of infectious diseases at Florida International University, noting that a record is kept of each specimen's location.
Once a sample is packed, it must be transported to an appropriate laboratory. Interestingly, FedEx Corp is authorized to transport specimens being tested for Ebola, said Chris Mangal, director, public health preparedness and response at the Association of Public Health Laboratories. Most public health officials have contracts with specialized transportation providers for such services, she said.
Ebola samples may be tested at labs outside the CDC, Mangal said. Select facilities that belong to the CDC's Laboratory Response Network, a group comprising more than 150 international, federal, state, military and local labs, have been given the appropriate equipment.
The CDC provides labs with a real-time reverse transcription polymerase chain reaction assay, or Real-Time RT-PCR, which allows researchers to identify the DNA sequence for the specific strain of Ebola that is under surveillance.
Because Ebola is an RNA virus, pathologists must use reverse transcription to turn the RNA into DNA so that the PCR test can be administered, said Dr. Gary Procop, a staff pathologist at the Cleveland Clinic. The PCR process involves heating up the DNA within the blood to separate its double strands, and then using primer strands (the starting point of DNA synthesis) to attempt to replicate a DNA sequence believed to be Ebola. A probe—a fluorescently labeled piece of DNA—is also used to attempt to replicate Ebola's signature sequence.
If the sequence of DNA believed to be Ebola replicates through this process, a pathologist may be able to confirm that the virus is present in the patient's DNA.
The Real-Time RT-PCR assay isn't just one possible type of Ebola test, it's a standardized protocol developed by the U.S. Army Medical Research Institute of Infectious Diseases, Mangal said. This means that officials can be confident that a test run in one lab will have the same result when evaluated in another.
Ebola is often detectable through a Real-Time RT-PCR test three to 10 days after a patient shows Ebola-like symptoms. However, CDC guidance says that a blood specimen should be taken as soon as a patient is suspected of having Ebola exposure.
Once a sample has been thoroughly tested, it is destroyed via autoclave sterilizer or incineration.
Though public concern is rising about the potential spread of Ebola, Mangal said U.S. laboratories are prepared, and many have handled samples more dangerous than Ebola.
“I really believe that our public health laboratories are ready for this,” Mangal said. “This is the type of work they do on a routine basis. This is their job.”
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