Testing sewage for the genetic RNA material of the SARS-C0V-2 virus has not proven to be a waste of time. It has become another tool for tracking COVID surges/surges/swells in an area or community that uses a shared sewage and sewage disposal system. Through the National Wastewater Surveillance System (NWSS) launched in September 2020, the United States tracks trends of decreasing or increasing infections to anticipate a new flood of cases to come about a week later.
A current example would be two recent Minneapolis Star Tribune sequels. The first, from May 7, was titled “Viral load of subway wastewater is up 21%,” compared to the previous week. The May 11 edition featured an article with the headline “COVID hospitalizations on the rise.” The first article said: “Sewage has proven over time to be a more timely indicator of COVID trends, revealing the onset and peak of this winter’s Omicron pandemic wave about a week before the number of infections don’t change. … The sewage and infection figures are now in sync. Last November, researchers from several universities and the US CDC detected the omicron variant in wastewater from Northern California, Houston, Texas (not Minnesota), New York and other locations as early as 11 days. before the first human case detected in the United States.
People also read…
Wastewater tracking has been used in the past to track polio, gastrointestinal infectious microbes, mercury, and even illicit drug use. When he was relatively new in the 1990s, he helped find where poliovirus was infecting a community so that vaccinations could begin before a lot of disease arose. This vaccine has been accepted almost universally, unlike our current COVID vaccines, which has led to the virtual eradication of poliomyelitis. It also strengthened public health surveillance efforts to detect antimicrobial resistant bacteria, influenza, Candida auris yeast, and foodborne infections like norovirus and salmonella.
About 80% of the populations in the United States are on sewer systems. The rest have individual disposal septic tanks – and who knows what – on the farm or in the hills. A sewage treatment plant can serve a large urban population, or a correctional facility/jail, educational institution, etc. Our current pandemic, although in decline, still poses public health challenges that we are trying to anticipate as the virus continues to mutate into new variants. At the beginning of an article, “everyone poops”, and we hope in the sanitation system. Between 30 and 60% or 40 and 80% of infected people excrete the virus in the stool. No matter how serious the case. Fecal shedding of detectable viral RNA can occur up to 45 days after symptomatic cases. Adults and children lose the same amounts.
People with asymptomatic infection also release viral RNA. Instead of the 20-45% postulated asymptomatic infections cited lately, we now have even less idea of the number of such infections, with increased immunity, less severe disease expressions, home testing and indifference tired by the pandemic to get tested. An educational institution found that their system’s viral load increased following a dormitory outbreak, tested students and found 70% positive tests. The pooled RNA also includes those infected but not yet symptomatic. Studies of antibody-positive unvaccinated people suggest that many infections go unreported.
There may be as many as 650-700 test sites currently in the NWSS. The sewage test for COVID has rapidly expanded worldwide with more than 2,200 sites in 55 countries using it since last August. The actual PCR test method is not considered too complicated scientifically (but I still won’t try to explain it here). It can be done on any COVID RNA. It can identify not only known variants, but also new (not necessarily improved) mutations that have not yet invaded any human. This makes it possible to anticipate the possible ease of transmission and the severity of this new virus on the block.
The data generated by wastewater monitoring is complementary to human and even real animal testing (rat, mouse, bat, etc.) as a guide to where to look and invest resources. The data is only as good as the generated results. The whole technique is still evolving in order to improve this data. They, in turn, help us try to keep up with this seemingly ever-changing microbe. This can help guide the development of new vaccines for new variants. Vaccines are imperfect, but remain our best “chance” to stem the virus.
So, testing sewage has not proven to be a waste of time, but an asset in our quest to defeat this virus. Reminds me of the guy who made a belt out of old broken watches and called it a “time waist”. (It just had to be done.)
Dr. Bures, a semi-retired dermatologist, has worked since 1978 in Winona, La Crosse, Viroqua and Red Wing. He also plays clarinet in the Winona Municipal Band and some Dixieland bands. And he appreciates a good pun.