A new piece of research looks at the infection dynamics of the SARS-CoV-2 virus within the home environment. The study is titled “Distribution of SARS-CoV-2 RNA Signal in a Home with COVID-19 Positive Occupants”, based on assessing data and interpreting what this signals about infection rates.
The study was conducted long after the occupants were determined positive, where the researchers took samples two months after the onset of symptoms and one month after the end of symptoms. It is of interest, in terms of the robustness of the virus, that they continued to detect viral RNA on just over 50 percent of the surfaces samples.
It is unlikely that the viral RNA recovered represented viable viral particles. The technology used, quantitative reverse transcriptase polymerase chain reaction (qRT-PCR) is effective at informing virologists if the virus was ever there. However, the detection of the viral RNA does not directly inform about its viability and hence the current risk.
Where the research is of great value is with understanding the dispersal of SARS-CoV-2 onto surfaces and dust within the home setting, especially in light of the knowledge gap in this area.
With the household studied there had been two confirmed COVID-19 cases (one adult and one child). The researchers took swab and dust samples from different locations with the home. It was noted that the level of viral RNA recovery varied across the fomites (infected materials) according to location, the type of surface material and whether or not the surface was subject to regular cleaning. In total, 24 surfaces were samples across the study period and almost half (46 percent) recovered viral RNA.
Importantly where cleaning was undertaken, this attenuated the recovery of the virus from surfaces. Where viral RNA was recovered most frequently was from dust recovered from floor (up to 100,000 gene copies per gram of dust). This is probably because larger respiratory droplets exhaled from an infected individual will invariably settle relatively quickly to the floor or other interior surfaces.
The researchers also recommend that assessing the concentration of SARS-CoV-2 (when normalized per unit mass of dust) recovered from HVAC filters may act as a useful means to estimate SARS-CoV-2 airborne levels in the indoor environment.
