Phase 2 - Systematic literature review
This Phase 2 review includes analysis and summary of findings from available scientific literature on SARS-CoV-2 (the virus that causes COVID-19) through mid-August 2020. This review focused on studies of how the virus is spread, virus attenuation on commonly found materials, and effectiveness of prevention and decontamination measures.
Key takeaways from the review
How the virus spreads
- Droplets. SARS-CoV-2 is generally understood to spread primarily through virus-containing water droplets expelled from infected persons from sneezes, coughs, speaking, and other respiratory activities. Evidence has also suggested that other pathways for spreading the virus may include:
- Aerosols. Breathing air that the virus is suspended in, such as after an aerosolization event (e.g., a sneeze)
- Fomites. Touching surfaces of objects where the virus has been deposited (sometimes called fomites), which can occur through exhaling or otherwise depositing virus-containing droplets on the surface.
- Environment. Environmental factors, including temperature and humidity, have been identified as influential in the spread of SARS-CoV-2. Specifically, higher temperatures, higher humidity, and increased intensity of ultraviolet (UV) light (e.g., sunlight) seem to lead to SARS-CoV-2 decaying more quickly. However, additional research is needed to understand the complexities of these variables’ impact on the virus and its transmission.
- Ventilation. Some evidence has suggested that HVAC systems and other air circulation mechanisms can contribute to spreading the virus through the air. On the other hand, poor ventilation may also lead to airborne virus remaining in indoor environments longer. However, the impact of these systems on people contracting the virus requires further study.
- Surfaces. Very few studies from the review period reported novel empirical research about the survival of SARS-CoV-2 on surfaces, which highlights the REALM lab results’ contribution toward this area of investigation.
Prevention and decontamination
Researchers suggested several options for reducing the presence of SARS-CoV-2 in environments, which may help prevent transmission among people in those environments:
- Frequent handwashing or hand sanitizing
- Wearing a mask that covers the mouth and nose
- Social distancing and reduced indoor occupancy
- Good air ventilation and open/outdoor spaces
- Applying certain forms of UV light or increased heat
- Applying disinfectants to contaminated surfaces and objects.
Notes for the reader
As you read this systematic literature review, keep in mind a few key points:
- The research and information captured in the findings include both peer-reviewed and non-peer-reviewed studies. In the interest of publishing emerging research related to the COVID-19 pandemic as quickly as possible, publication has been expedited rather than waiting for time-intensive peer review.
- The studies included in the review have been conducted by different researchers, under different conditions, likely using different concentrations—and possibly sources—of the virus. This makes it difficult for a reviewer to make a straight comparison across studies; and, interpreting the results may be challenging for readers without a science background.
- The review includes findings for industries, such as health care, that operate under considerably different constraints and risk factors than do libraries, archives, and museums (LAMs). However, it was important to consider a broad range of available research to determine what may be applicable to LAM operations and identify what research gaps exist. The research captured in the review does not represent recommendations or guidance for LAMs.
- The Phase 1 literature review was released in June 2020.
- A helpful resource for those interested in tracking the "known unknowns" about this virus is the DHS Master Question List for COVID-19 (caused by SARS-CoV-2)
Download the systematic review
Download the key takeaways