Scientist says the answer for Covid-19 testing lies in sewage surveillance
With the country facing a shortage of Covid-19 tests kits, a scientist from the University of the Free State believes that the answer to bolster testing lies in sewage surveillance.
Dr Anthony Turton from the Centre for Environmental Management at the institution said there were 824 wastewater treatment works in the country and each one served a population of “known size”.
“By taking samples of sewage according to a defined protocol, it is now technically possible to determine the viral load of the entire population in the catchment area of that sewage works.
“This data can be compared weekly, and from this we can determine if the total viral load is increasing or decreasing,” Turton said.
Turton believes that this was a “much easier” method than doing individual testing across the country.
According to him, the coronavirus has a specific structure that gives it a number of properties.
He said one of the properties was associated with the “fatty outer coating”, which is susceptible to detergents, ultraviolet light and alcohol.
“What is known to scientists, but not yet apparent to the public is that the virus is shed in human waste. This is known as viral shedding, and is now known to result in a traceable presence in both urine and faeces before a patient manifests with symptoms and after a patient has been treated.
“This does not mean that the virus is still infectious, although there is some mention of faecal-oral transmission in peer-reviewed literature, at least of the SARS virus.
“This is not yet fully understood, so the faecal-oral transmission pathway is mostly ignored by policy response, which is typically based on western premises such as a fully functional wastewater works. That may not be the case in developing countries, but the jury is still out on the faecal-oral transmission route,” Turton said.
Turton said technology was also able to detect “minute elements” of the virus found in human waste.
According to Turton, samples are taken from the inlet to wastewater works where raw sewage is mixed.
He said it was important for sampling to be regular and accurate. He said the samples are then prepared in a “specific way” and sent to a laboratory capable of detecting precise elements of the ribonucleic acid.
“Think of fingerprinting to understand this process. The coronavirus has a precise fingerprint consisting of strands of carbon-based nucleotides arranged in a known sequence. It breaks down after the virus is destroyed but remains present like a bowl of minute pieces of spaghetti. Once detected and identified, it is then amplified or increased through a process known as polymerase chain reaction.
“In effect, this merely replicates what is originally present, like a photocopy machine.
“This is technically complex, and mistakes can be made each step of the way. However, if done properly, an accurate picture emerges. This picture is not about individuals who are positive or negative, but rather about the total viral load present in a defined cohort of people at a precise moment in time.
“It is not as granular as individual testing, but it is a convenient way of gathering data about the rate of change and specific epicentres of change or emerging hotspots.”
He said the technology has been successfully used in the Netherlands and is now being rolled out in other countries in the world.
The SA Business Water Chamber, a non-profit organisation secured the right to use this technology for SA.
It has since been made available to any laboratory, privately owned, university owned or part of a national science council,
“This will be of critical importance as the government decides to open up the economy, because sewage surveillance can detect a second wave before it is manifested as people reporting to doctors with symptoms,” he said.