Can we predict a COVID-19 outbreak with wastewater analysis?

Water and Bubbles

Certainly, yes! This is what we refer to as sewage or environmental epidemiology. And if it has worked for other viral diseases like poliovirus, it means it is much feasible in regards to the deadly SARS-CoV-2 virus.  

In the very initial days of the COVID-19 pandemic, countries all over the world resorted to traditional PCR testing as a tool to detect the number of cases in different locations. Right away we knew the data was flawed as so many people had not yet been tested. Many individuals in fact did all they could to avoid the test due to the stigmatic repercussions the disease attracted in the early days. 

Also, the testing kits were far less compared to the population. Even those who showed symptoms and wanted to get tested were not assured of the test. 

Another issue with the clinical testing of coronavirus is that it was more reactive than proactive. Mass testing would only be done after the outbreak. In such a case, the tests were more of a confirmation of the outbreak rather than a preventive tool. 

It is for these and other reasons that disease experts carried out research on whether the virus exists in human waste. Indeed, it was confirmed that human feces start showing viral material about 3 days after one is infected with the SARS-CoV-2 virus. This fact alone psyched up scientists to pursue environmental epidemiology as a tool to predict COVID-19 outbreaks. As you now know, it takes 5-6 days for a COVID-positive patient to start showing symptoms. And this is the time most people consider taking the coronavirus test. Coupled with the usual delays in testing and reporting, it takes an average of 2 weeks to ascertain that an individual has the virus. Therefore, detection of coronavirus in wastewater serves as an early warning sign of infection. 

Logistics of wastewater surveillance for mapping COVID-19 outbreaks

To ensure that the wastewater analysis results are useful to the concerned health authorities, the following factors have to be considered:

  1. Health officials must first identify critical reservoirs and pathways where human waste is deposited. These include wastewater treatment plants, sewage lagoons, and septic tanks. 
  2. The approximate number of people using the above-mentioned facilities should then be determined. 
  3. Sampling should be done at all critical points so that the results are more representative of the actual infection rate in the population. Both liquid and solid samples should be taken as there is evidence that SARS-CoV-2 viral material has more affinity for solids than liquids. The best point to sample is where the waste has not yet undergone any treatment – in other words, raw sewage.
  4.  Sampling should be done at regular times, in line with flow fluctuations. For instance, a sewage treatment plant serving 1 million residents should be sampled more frequently than a sewage lagoon serving 10,000 residents.
  5. The samples collected should undergo some pretreatment before testing is done. This is mainly aimed at getting rid of substances that may result in inhibition of molecular assays normally used in the tests.
  6. Testing is finally using the PCR method – quantitative polymerase chain reaction. This is similar to the clinical tests done on individuals. Any other appropriate molecular testing method can still be used. 
  7. An analysis is done to project the proportion of the population with the COVID-19 virus

Advantages of sewage surveillance in tracking COVID-19 spread

  1. As earlier indicated, environmental epidemiology can tell whether there is an outbreak far earlier than traditional clinical testing can. This helps government authorities prepare hospitals for an increased number of patients. Containment measures such as compulsory social distancing, mandated mask-wearing, and total lockdowns can be imposed in good time.
  2. Sewage surveillance looks at biological samples from millions of people at a time. This is way more than mass testing can achieve, no matter how fast it is done.
  3. Wastewater analysis for tracking COVID-19 takes care of those not willing to get tested, and also the asymptomatic cases.   

Challenges of wastewater analysis as a tool of tracking coronavirus outbreaks

  1. Wastewater analysis is more straightforward in urban areas with centralized waste disposal systems. It gets more complex for rural areas where sewage collection is decentralized.
  2. Wastewater is diluted, and therefore PCR testing may not be as straightforward as that done on samples obtained directly from the body. However, with clever scientific tweaks of the setup, fairly accurate results can be obtained

I conclusion, wastewater analysis is a great tool that can be used to predict COVID-19 outbreaks. However, it should in no way entirely replace clinical testing. It should only be used as a complementary tool. And if done properly, health officials will be able to make necessary preparations in advance in case of an outbreak.