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It is true that these findings should be treated with great caution. The first is that, until now, they have only been published in the medRxiv medical archive, where the resulting articles are still pending review by independent reviewers before being published in a scientific journal. Until the review process is complete, all of the research findings should be viewed with at least some skepticism.
How did you research and what did you find?
One of the first discoveries that was made to explain what the SARS-CoV-2 virus is in animals is the fact that it can be found in the feces of infected people. As the virus travels through the gastrointestinal tract (where it can also cause gastrointestinal symptoms), it loses its outer protein layer, but the virus’s genetic material, the RNA strand, remains intact through the intestine, making it very difficult to detect in stool.
As far as is known, the virus in this state, only genetic material without a protein coat, has lost its ability to infect humans.
However, the very fact that non-infectious RNA strands of this and other similar viruses can be detected in untreated wastewater is very helpful in monitoring outbreaks of various viral diseases. And even from the results of the sewage analysis, it is possible to predict where a new outbreak will occur in a week or two: the remnants of the virus particles are eliminated in the faeces and during the incubation period before the outbreaks appear. symptoms.
These “pre-symptomatic” people are included in official statistics only if their condition deteriorates sufficiently and they undergo a virological examination, and can be admitted to the hospital.
As a result, many countries around the world, including Spain, have begun to closely monitor the content of their wastewater and look for coronavirus particles in it. Specifically, the researchers, wastewater epidemiologists, analyzed frozen samples collected from 2018. January to 2019 December to determine when the first people with the new coronavirus appeared in their city.
The guaranteed results of the presence of the virus in water are obtained from 2020. January 15, 41 days before the announcement of the first official case of the new coronavirus in Barcelona. Until that date, almost all the water samples were “clean”. Except one: in 2019. March 12, which showed that the polymerase chain reaction (PCR) test showed residues of new coronavirus particles. The fact that a person is infected with SARS-CoV-2 is generally detected by the same PCR method.
Saliva, mucus, frozen wastewater and, in general, any medium in which the virus may be present are suitable for the PCR test. All unnecessary material is removed from the sample, and then the RNA strands found in the sample (single-stranded genetic material) are converted to DNA (double-stranded genetic material).
Then “DNA amplification” is performed, in which fragments of genetic material multiply multiple times over several cycles and, according to research, can only exist in the genetic code of a particular virus. Amplification is done until those DNA particles become large enough to be captured by a fluorescent probe.
Little specific
Scientists who check for coronavirus infection generally look for more than one specific gene. And in this case, the researchers looked for three genes. OR 2019 Only one gene from this trio, RdRp, was found in the March water sample. Two regions of this gene were searched and both were detected in only 39 amplification cycles (and each additional amplification cycle reduces the level of specificity). 40-45 amplification cycles are commonly used for research.
This “positive” water test result can be explained in several different ways. The first is that the effluent actually contained very small amounts of virus particles. The second is that the test equipment was already contaminated with SARS-CoV-2 particles in the laboratory. This sometimes happens: In a laboratory where you constantly work on this particular virus, it is very difficult to prevent incredibly small particles of the virus from reaching where they shouldn’t be.
The third explanation is that there are other RNA or DNA chains that are so similar to the RdRp chain that they can mix during the amplification cycle.
Additional tests would be needed to confirm that the water studied by the Spanish scientists contained traces of SARS-CoV-2, which must be replicated by another independent laboratory.
Why be treated with caution?
Even if we ignore the fact that this study has not yet been published or reviewed, its credibility is still undermined by something else interesting. The study authors provided no evidence that there was at least a slight increase in the number of patients with respiratory diseases in and around Barcelona in March or April of this past year.
We also know that SARS-CoV-2 is a highly contagious virus, at least in its current form. So, if the researchers were not mistaken, then it can be concluded that the virus was widespread enough for its particles to appear in 800 ml of random wastewater, but not enough to cause problems for doctors for nine months after the emergency and without any control measures.
Therefore, these results should be treated with extreme caution until reviewers and other independent laboratories have completed their work.
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