The major risk arising from Covid-19 is the fact that people can be infected but show no symptoms. It is these asymptomatic carriers that are the vectors accelerating infection in society. This is the central problem that has to date defied a solution.
Since the government cannot test every citizen in the country, the answer lies in sewage surveillance, says Dr Anthony Turton from the Centre for Environmental Management at the University of the Free State (UFS).
EASIER THAN TESTING MILLIONS OF PEOPLE
“We have 824 wastewater treatment works in South Africa. Each of these serves 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,” says Dr Turton.
According to him, this is much easier to do than the individual testing of millions of citizens, the results of which only give a snapshot of information relevant to those specific people at that precise moment in time.
Dr Turton explains that the virus has a specific structure that gives it a number of properties. One of those properties is associated with the fatty outer coating, which is susceptible to detergents, ultraviolet light, and alcohol. This is known and forms part of the protocols to limit transmission.
“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,” explains Dr Turton.
What is of greater importance to society as a whole, Dr Turton continues, is the evolution of technology that is capable of detecting minute elements of the virus found in human waste. This is known in technical circles as sewage surveillance. A person being tested has to go to a designated facility where they come into contact with other potential carriers; so even if they test negative today, this does not mean that they will not become infected on their way home.
“Such testing is costly, logistically complex, and is known to be out of reach even to advanced economies such as the USA, Britain, and Germany. But without testing, how can government still maintain its core mandate to protect citizens without destroying the economy by a perpetual lockdown?”
“This is a dilemma that we need to confront, because the impact of economic meltdown can be bigger than the virus itself. The South African economy, which is already on its knees, cannot afford unemployment rates that might trigger social instability and unleash latent revolutionary zeal,” says Dr Turton.
A CONVENIENT WAY OF GATHERING DATA
According to Dr Turton, samples are taken from the inlet to wastewater works where raw sewage is mixed. If more precise details are needed, sampling can occur on specific feeder lines, for example, from different suburbs representing different demographic samples of a larger and more complex whole. This ability gives sewage sampling a high level of nuance, because the pixel density of data built up over time is granular and precise. The important thing is that sampling must be regular and accurate, because each provides a single frame in the movie that we ultimately want our decision makers to watch.
“Those samples are prepared in a specific way and sent to a laboratory capable of detecting precise elements of the RNA. 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 PCR (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.”
This technology has been successfully used in the Netherlands and is now being rolled out in other countries in the developed world. The right to use this technology has been secured for South Africa by the SA Business Water Chamber, a non-profit organisation, which entered into an agreement with KWR, the Dutch laboratory that has refined the technique. It is now being made available to any laboratory, privately owned, university owned or part of a national science council, with the intention of supporting decision-making by government. 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.
• The Business Water Council is a newly created structure for all entities involved in the business of water service provision, and is part of the Public Private Growth Initiative (PPGI) that aims to bring the private sector close to government in a collaborative effort to stimulate the economy and create jobs in a sustainable way. Funding entities have shown interest in supporting this process, given the strategic importance of sound decision-making for economic recovery after COVID-19 has passed.
Any university with PCR capabilities can become a certified user of this technology, as can any commercial laboratory being rolled out as a humanitarian issue rather than a commercial one, even if it has an impact on the recovery of the economy.