To inform the research for the REALM project, Battelle has prepared the document, Test Plan for the Natural Attenuation of SARS-CoV-2 as a Decontamination Approach. This test plan describes how the Battelle laboratory will test for the longevity of the COVID-19 virus on materials and how long it takes for the virus to naturally attenuate—essentially, how long the material needs to be left alone before the virus is undetectable. Key points about the testing:
- The are five materials studied in each test. For each material, five samples are tested (called "coupons").
- This study uses a TCID50 cell-based assay where the virus is put into a cell culture to see if it grows. Battelle has deep experience with this test method, which measures live, infectious virus.
- Droplets of live, infectious virus are applied to material surface via "fake spit" and then allowed to dry for one hour. While we do not know how much SARS-CoV-2 virus is in a typical human sneeze, the researchers are seeking to use an amount that could be akin to an infectious or possibly highly infectious sneeze.
- The researchers check to see if the virus remains active when extracted from the sample material mixed in the cell culture. In some cases, there might be a chemical in the material that kills the cells, which means they can't track the virus. This is called cytotoxicity.
- For Tests 1 to 5, all tested materials have been held at standard room temperature (68°F to 75°F) and relative humidity conditions (30 to 50 percent). It is possible to change to these conditions for future tests, to study the effect of, say, higher heat or lower humidity on the survivability of the virus.
- Materials are put in a test chamber, stored in stacked or unstacked configurations. There is no outside light or air getting into the chamber.
- “Stacked” means direct and full surface-to-surface contact. Even a little bit of space between surfaces will make a difference.
- The interior of the chamber is akin to items being inside an enclosed box, bag, or bin that is sitting in standard office environment.
- After the initial drying time ("T0"), the materials are checked at each designated time point for the test. Time points are chosen in advance to examine each material to see how much active virus remains.
- There is a point at which there are not enough viral particles remaining to perform the cell culture method. This point is termed the “limit of quantitation” (LOQ) and is depicted by a red horizontal line on the graph. After that point, the researchers just look for any presence of viral particles under the microscope and record a yes or no. Once they don’t see anything that way either, it is termed “below the level of detection” (LOD).
Download the test plan (PDF)