Studies Finding Remnants of SARS-CoV-2 in Sewage Suggest COVID-19 May Not Have Originated at Wuhan Market, Some Scientists Dispute the Findings
Researchers from multiple countries looked at sewage samples collected from 2018 through early 2020, with findings that may interest microbiologists and medical laboratory scientists
Clinical laboratory tests for the SARS-CoV-2 coronavirus can identify COVID-19 cases in individuals. But in multiple countries, researchers have tested untreated sewage for remnants of the pathogen, and some scientists have arrived at a surprising but unconfirmed theory—that the coronavirus appeared in Europe long before the first reported cases in Wuhan, China.
In an article for The Conversation, titled, “Coronavirus: Wastewater Can Tell Us Where the Next Outbreak Will Be,” Davey Jones, PhD, Professorial Chair of Soil and Environmental Science at Bangor University in the UK, wrote, “For the past three months, we have been using a test called polymerase chain reaction (PCR) to find traces of SARS-CoV-2 in untreated wastewater. We believe this could form a valuable part of disease surveillance. Most UK towns and cities are served by just one or two wastewater treatment works, so a single sample—about a liter of water—can provide information on millions of people.”
The Lancet reported on similar research being conducted in Barcelona, Spain. At the University of Barcelona (UB) researchers analyzed raw sewage samples taken between April 13 and May 25 from two large wastewater treatment plants in the city. In addition, they analyzed frozen archival samples taken from one of the plants in 2018 (January-March), 2019 (January, March, September-December), and 2020 (January-March).
They reported presence of the virus in samples taken as early as Jan. 15, 2020, 41 days before the Barcelona’s first known case was reported on Feb. 25. Most surprisingly, they reported the presence of two genetic fragments—IP2 and IP4—in a sample taken on March 12, 2019.
That would seem to conflict with early reports that the first human infections occurred in Wuhan, China, in November to December of 2019.
All other Barcelona samples from 2018 and 2019, with the exception of one, tested negative, said Albert Bosch, PhD, in a press release. Bosch is professor at the Faculty of Biology at UB, head of the Enteric Virus laboratory at UB, president of the Spanish Society of Virology, and one of the lead study’s researchers. In the March 12 sample, he said, “the levels of SARS-CoV-2 were low but were positive, using two different targets.”
The Barcelona researchers reported their findings in a study published June 13, 2020, on the medRxiv preprint server, titled, “Sentinel Surveillance of SARS-CoV-2 in Wastewater Anticipates the Occurrence of COVID-19 Cases.”
Similar Findings in Brazil and Italy
Researchers in Brazil and Italy also have reported the early presence of SARS-CoV-2 in wastewater samples.
In northern Italy, researchers tested samples taken from five wastewater plants between October 2019 and February 2020 and reported positive test results in samples taken on December 18 in Milan and Turin. The country’s first case of COVID-19 was documented on Feb. 21. Those findings were published June 26 on medRxiv, titled, “SARS-CoV-2 Has Been Circulating in Northern Italy Since December 2019: Evidence from Environmental Monitoring.” The study has not been peer reviewed.
Researchers in Florianópolis, Brazil, tested wastewater samples taken between late October and early March. They reported presence of the virus in two samples from Nov. 27, 2019. Those findings, also not peer-reviewed, were published June 29 on medRxiv.
Questioning China Origins
The findings from Spain and Italy led Oxford University epidemiologist Tom Jefferson, MD, Honorary Senior Research Fellow, Center For Evidence Based Medicine, to speculate that the SARS-CoV-2 virus did not originate in China. “I think the virus was already here—here meaning everywhere,” he told The Telegraph. “We may be seeing a dormant virus that has been activated by environmental conditions.”
He repeated his assertions in an interview with CGTN, an English-language news channel controlled by the Chinese government. “We know that for certain it was recognized as a newly identified disease in Wuhan,” he said. “I think there’s little doubt about that. But being newly identified in Wuhan and being originated from Wuhan are two different things. It’s not necessarily cause and effect.”
In addition to questioning the origins of the virus, “Dr. Jefferson believes that the virus may be transmitted through the sewage system or shared toilet facilities, not just through droplets expelled by talking, coughing, and sneezing,” The Telegraph reported.
“There is quite a lot of evidence that huge amounts of the virus in sewage [are] all over the place, and an increasing amount of evidence there is fecal transmission,” he told The Telegraph. “There is a high concentration where sewage is four degrees [Celsius], which is the ideal temperature for it to be stabled and presumably activated. And meatpacking plants are often at four degrees. These meat packing clusters and isolated outbreaks don’t fit with respiratory theory, they fit with people who haven’t washed their hands properly.”
Pushback on Jefferson’s Claims
“It’s implausible that there was a hidden pandemic before it actually started,” he told Euronews. “If that’s the assertion, that’s a pretty wild accusation actually, because it flies in the face of all we know about how this epidemic has evolved.”
Lundgren also questioned the findings from Spain, Italy, and Brazil. “They haven’t found the same virus,” he said, only “molecular evidence that there is shared genetic material.”
The Spanish, Italian, and Brazilian studies have not been peer reviewed, and some experts have suggested alternative explanations for the positive test results, including “the potential for a false positive due to the virus’ similarities with other respiratory infections,” Reuters reported.
“When it’s just one result, you always want more data, more studies, more samples to confirm it and rule out a laboratory error or a methodological problem,” Joan Ramon Villalbi, MD, PhD, MPH, of the Spanish Society for Public Health and Sanitary Administration told Reuters. “But it’s definitely interesting, it’s suggestive,” he added.
Writing in The Conversation about the Barcelona study, Claire Crossan, PhD, Research Fellow, Virology, Glasgow Caledonian University, raised the possibility of lab contamination and questioned why there were no reported spikes in respiratory disease cases after the sample was taken.
“If this result is a true positive it suggests the virus was present in the population at a high enough incidence to be detected in an 800ml sample of sewage, but then not present at a high enough incidence to be detected for nine months, when no control measures were in place,” she wrote.
Though nothing definitive may come from these studies, they do indicate that there’s still much to learn about the origin of the SARS-CoV-2 coronavirus. Clinical laboratory leaders would be wise to keep an eye on these developments.