Prisca Tiasse, PhD in her lab Tuesday at Biodidact on DP Road. Photo by John McHale/ladailypost.com
By CAROL A. CLARK
Los Alamos Daily Post
Biodidact, a local R&D and environmental testing laboratory recently took part in an effort, with the collaboration of Los Alamos County wastewater treatment facility staff, to track COVID-19 in local community wastewater.
“We are fortunate to have researchers working toward capabilities for wastewater testing of COVID-19 in collaboration with the County,” Los Alamos County Council Chair Sara Scott said. “Continuing to develop new and effective tools for monitoring the virus is important for addressing both current and longer term challenges associated with the pandemic.”
Earlier this summer, Biodidact took part in a global initiative (MetaSUB) that aimed at testing high-touch surfaces in the community for the presence of SARS-CoV-2, commonly referred to as COVID-19. That effort was one of many COVID-19 environmental monitoring programs around the world. Biodidact owner Prisca Tiasse, PhD, explained that although in that initiative most surface testing efforts came back negative for COVID-19, some obvious hot spots emerged such as floors, doorknobs and bathroom walls and ceilings.
“Bathroom contamination is consistent with the fact that several recent studies have documented the presence of both COVID-19 and virus in stools of infected individuals,” Dr. Tiasse said. “In response to such reports, back in March 2020, the Food and Drug Administration (FDA) released a safety alert regarding the use of fecal microbiota for transplantation (FMT), acknowledging that .SARS-CoV-2 may be transmitted by FMT’”.
Most infected people (both symptomatic and asymptomatic) excrete the virus in their stool, which can be tracked in local wastewater plants, she said.
The main advantages of wastewater monitoring for COVID-19 lay in the fact that:
- it has the ability to sample an entire community; and
- it has proven effective in predicting outbreaks of COVID-19 by up to two weeks.
Dr. Tiasse said wastewater monitoring is therefore a valuable tool in detecting early warning signs of emergence or re-emergence of the disease within a given community and a means to measure the efficacy of pandemic mitigation strategies.
“In light of those observations, international collaborative groups have come together to allow scientists to share and discuss protocols and results,” she said. “Because of varying local environmental conditions and varying viral loads between locations, protocols sometimes have to be tweaked and adjusted to allow for adequate detection.”
Biodidact collected two different samples on Oct. 23 and Nov. 10. After processing those samples, Biodidact performed two different tests in parallel: the standard RT-PCR tests, and a relatively new specific, sensitive and rapid colorimetric test (also used for COVID-19 testing in saliva). With pure RNA, both tests were consistent, Dr. Tiasse said.
“These techniques are very sensitive, provided there is enough sample material to test. The COVID-19 levels in the Oct. 23 sample were so low that the test initially came back negative,” she said. “After further concentration of the RNA extracted from the sample (to increase sensitivity), the test came back positive (proof that we could detect trace amounts of viral RNA in local wastewater).”
The results from the Nov. 10 sample showed a significant increase in viral load in the community, compared to the Oct. 23 sample and came back positive the first time around, she said.
“Our goal was to refine our protocol for low-viral-load communities such as Los Alamos and monitor any increase over time. Our protocol allows us to quantify the increase and should allow us to estimate the number of RNA copies detected (per mL of sample),” Dr. Tiasse said. “The next goal is to collect more samples around Thanksgiving and Christmas time (anticipating more visitors in town) and see whether we detect a bigger increase in viral load in the community. More testing down the road, after a vaccine has been distributed, also would allow us to assess its efficacy in reducing the community viral load.”
Dr. Tiasse said she would like to conduct longer-term wastewater testing for COVID-19 but needs to secure funding to finance that project.
“Published studies and other research groups working on similar work describe that wastewater testing efforts have a better informative and predictive value for the community if they are done weekly. That way one can see a trend (increased or reduced infections) before people seek to get tested, and regardless of whether people get tested or not, if they remain asymptomatic,” she said. “It gives a better picture of what is happening in the community. Right now we are reacting to the number of positive tests, this is a way to be a little more proactive. It is reported that with such testing, communities can get up to 2 weeks of advance notice, meaning either tightening restrictions or relaxing them when appropriate. With such testing, employers like hospitals or larger institutions with local wastewater collection can render their workplace safer. It was reported that the University of Arizona was able to stop a COVID19 outbreak after testing wastewater in dorms, just a few days after students got back to campus.”
A large institution like LANL could benefit from such wastewater testing, Dr. Tiasse said, adding that she heard that LANL has its own wastewater collection, so that’s something that would be very beneficial for them in preventing a local outbreak – and she said she would be happy to help with that effort.
Dr. Tiasse explained that an important distinction to be noted when tracking the presence of COVID-19 in wastewater is that studies typically test for the presence of viral RNA, not for infectivity of the virus, which is believed to be mostly degraded by the time it reaches the wastewater plant. The current consensus regarding the presence of the virus in wastewater is that the majority of the virus in wastewater is not infectious and that fecal-respiratory transmission is unlikely but still under investigation.
“That being said, aerosol production during toilet flushing (also known as ‘toilet plume’) has been extensively studied and documented and remains a potential concern,” she said. “A 2018 study in hospital bathrooms comments that ‘toilets with greater energy flushes have been shown to generate higher concentrations of bacteria and particles into the air than toilets with less energy’.
Considering the fact that public bathrooms have greater energy flushes and rarely have lids, they are potentially an underestimated source of exposure, she said.
“Because aerosols are reported to linger in the air for hours, if those particles do in fact prove to remain infectious, we may need to seriously consider the potentially infectious toilet plume in communal bathrooms,” Dr. Tiasse said. “COVID-19 is, however, not the only infectious disease to be concerned about. Toilet plumes have clearly been implicated in disease outbreaks involving pathogens concentrated in feces (like Norovirus). Such infectious route is plausible in the case of COVID-19 but not considered likely (because of the amount of infectious viral particles one would have to inhale to get sick). Your best bet is still to wash your hands thoroughly if you have to use a shared restroom and don’t hang around for too long.”
A recent study from a longitudinal study of wastewater samples in Connecticut was the first to correlate a direct increase of viral RNA detected in municipal wastewater samples with a local increase in COVID-19 cases. The data suggested the potential predictive value of wastewater surveillance. Courtesy/Biodidact
Initial rapid screening of Los Alamos wastewater sample for presence of SARS-CoV-2 RNA. Samples were collected on Oct. 23 and Nov. 10. Samples 1, 2 and 3 are control samples to control for potential false positive or false negative results. Sample 4 determines whether SARS-CoV-2 is detected in the sample. [Pink = Negative (no detection); Yellow = Positive (detection)]. Courtesy/Biodidact
1: No template negative control (nuclease-free water) test with CDC SARS-CoV-2 primers
2: Positive control (SARS-CoV-2 RNA) test with CDC SARS-CoV-2 primers
3: Wastewater sample – Internal control test with rActin primers- Tests for detection of RNA in the wastewater sample – RNA properly extracted from sample if yellow reaction.
4: Wastewater sample – test with CDC SARS-CoV-2 primers