The presence of traces of SARS-CoV-2 in wastewater is proved to be an effective tool to determine the infection of communities. Although the virus is inactivated in water at room temperature, as is the case with other similar viruses, remnants of its genome can be detected by qPCR tests. This early detection system could be used for the preventive closure of areas with an incipient number of COVID-19 cases. In fact, tests in this regard seem to indicate that there is a very close relationship between the number of positives detected by individual PCR tests and those carried out on wastewater. The study of the presence of the coronavirus in water can reveal not only the presence of the disease in a community, but the true scale of infection. In fact, more than a dozen research groups around the globe are conducting analyzes of this type to monitor the evolution of the pandemic.
Wastewater collection plants receive the waste of millions of people. SARS-CoV-2 has been found in urine and feces as early as 3 days after infection. Although the amount of virus excreted in the samples per patient remains to be established. In this regard, the number of daily samples that must be analyzed for the data to be representative remains to be determined. However, monitoring the presence of the virus at the collection points can give a more accurate view of the spread of the virus, since asymptomatic patients do not get to undergo individual tests.
Finally, the analysis of the wastewater can be used in the future as a non-invasive test to alert about possible new future outbreaks. On the other hand, the review of wastewater samples can give us a new vision about the beginning of the pandemic. The virus was first identified in November 2019 in China. It was assumed that in the Wuhan market it had passed from live animals to humans. From there it is assumed that it spread to the rest of the world. This is the story as we knew it until now. However, evidence is emerging around the world that the virus was already circulating throughout the world at the time the alarm was raised in Wuhan. China has been much blamed for the global COVID-19 pandemic, many threats and many lies have been launched about the country and the release of the virus. New evidence is now coming to light that the virus was already in Europe and America at the same time it was being detected in China.
Precisely in December wastewater samples from Turin and Milan (Italy) were tested positive. Blood samples collected during the same year from multiple countries on both sides of the Atlantic that have reacted to antibodies against SARS-CoV-2. Now a team of Italian doctors have sequenced a genome fragment of a coronavirus from a sample obtained on December 5, 2019 from a child (4 days after the epidemic was declared in China). The fragment matches 100% with the genome that was sequenced in Wuhan. This means that the same strain was already circulating at least between China and Italy at that time, since we found the same virus in both places.
To these data, it must be added that the review of samples taken from patients with influenza in the 2019 season are revealing possible previous coronavirus infections. Notable was the case of a positive from a Parisian resident who had been diagnosed with the flu when COVID-19 actually passed without having left the country since August. Identifying patient zero is key to knowing how the virus has been transmitted. The lack of relationship with China and this case make the authorities believe that the virus was already circulating in the country by then. In this regard, the WHO encourages reviewing the previous cases because it states that it is possible that some cases diagnosed of flu last year were actually COVID-19. Although you have to be careful with these data and do not assume that the disease spread before. In fact, the data on the 2019 flu season have left a number of people affected similar to previous years worldwide. So we can rule out that the effect of COVID-19 went completely unnoticed.
If we put together the wastewater sample data with those from the previous year, it seems that a slightly different story from the one we knew is beginning to form. All of this is largely reminiscent of the so-called Spanish Flu that ravaged the world 100 years ago. The strain of that flu did not emerge in Spain, but the European country was the first to sound the alarm about its presence and was the one that most widely covered global progress. Perhaps we are in a similar case and this so called Wuhan pandemic is not coming from there. In fact, the wild virus has not been found in pangolins or bats from the Wuhan region, from where it was believed to have jumped into humans.
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