Dr. Fiona Young is an Adjunct Associate Professor, College of Medicine and Public Health, Flinders University, Adelaide, Australia. She taught and researched in the disciplines of Medical and Environmental Biotechnology, with a focus on toxicology and mammalian cell culture.
In a post on the COVID-19 scientific blog, she reviewed the latest scientific research into coronavirus and transmission via wastewater systems.
Thank you Dr. Young for looking out for wastewater professionals!
From her post…
The early day 1 and 2 samples had the highest viral loads, and viral loads decreased thereafter. When the samples with the highest viral loads were collected the patients either had no symptoms (prodromal) or very mild symptoms. This study did not examine the ability of early stage infectious people to shed virus or infect others but if prodromal people did not cough or sneeze then the high viral loads in their throats would be less likely to infect others.
Although viral RNA was detected by qRTPCR for up to a month, infectious viruses were only detected for 8 days, even when the viral load was so high that the infectivity test would have worked. The authors speculated that it is possible that the patients’ immune systems weakened the virus and made them less able to infect after 8 days.
Viral RNA found in faeces was probably from dead virus. The combination of tiny amounts of SGmRNA in 3 of 9 samples, and complete absence of any infectious virus detected in the cell culture test, leads to the conclusion that this study did not provide evidence for live infectious SARS-CoV-2 in faeces.
The authors note that although there is evidence for some SARS-CoV-2 infection of cells that line the gut, it is not known if the environment inside the lumen of the gut is hostile to virus, or if passage through the lower gut kills the virus, and more studies are needed to determine this.
Take Home Messages
There was no evidence for infectious live SARS-CoV-2 in human urine or faeces in this small study of only four people (that faeces samples were collected from).
WWTP operators are unlikely to be at risk of SARS-CoV-2 infection from this source but larger studies are needed to increase the ‘weight of evidence’ to substantiate this conclusion.