Sewage analysis for traces of covid 19 one of the most reliable systems


According to the Spanish newspaper El Confidencial, regional and central governments in Spain have been massively investigating their wastewater in recent months, but the results of those investigations are not known to the population. The newspaper subscribes this article that the investigating companies are instructed to only release the information to politicians, who in turn have not yet released it.

For the analysts, epidemiologists and health managers, a good interpretation of those results from a new but decisive measurement model is the main challenge.

“Even in asymptomatic people, traces of coronavirus appear in their stool,” explains Héctor Rey Gosálbez, specialist in purification processes and associate at the Polytechnic University of Valencia. “The faecal water circulates through the sewers by sector, so you can take samples by neighborhood to know if the presence of covid has increased in that area,” he added.

The regions of Valencia, Murcia, Catalonia and Navarre are the first to start testing their sewage water. This means that these regions were able to collect data over a longer period of time. The longer that period is, the better analysts can interpret that information. For example, if a certain level of Covid in wastewater was seen in a specific part of a city or zone in March, where there was also a certain number of hospitalizations or deaths, and it is now found that this percentage is approaching again, it can be deduced that the health situation is deteriorating .

Angel Villanueva is climate change director of Aquatec, part of the Suez group, the company that does more of this type of analysis in Spain, and says: “In Catalonia and the Valencia region, we started in full lock-down in mid-March with measurements on certain points in the big cities. We couldn’t measure the start of the pandemic, but we did research from when the peak of infections and deaths was highest and started to level off again. ” Villanueva is pleased that regional governments are increasingly aware of the importance of this system in predicting new outbreaks of contagion. “It provides a good indication of the level of contamination and thus a very useful picture for the authorities”, the specialist summarizes. Villanueva explains that with the awareness of the authorities about the method, their interest in it has also increased and with it the number of analyzes performed and the more analyzes, the more detailed the picture that emerges and which can be acted upon by the authorities.

“There is scientific evidence in several countries of the presence of coronaviruses in sewage – for example, residues of the virus were seen in sewage water in Italy 40 days before the first case became known – and we need to be able to detect outbreaks as early as possible, preferably when these have yet to start, ”said Villanueva.

Ambitious early detection program

Last week, Madrid announced that 290 sampling points in sewer networks and treatment plants will be activated. This is the largest initiative in this regard developed in Spain so far, both in terms of number of sampling points and frequency and in the population served. This means that the sewage water of more than 6.5 million inhabitants is monitored. “Samples are analyzed weekly and the results obtained are made available to healthcare managers,” said the region’s statement, describing the project as an “ambitious monitoring program that allows for early detection so that the health system can anticipate the health system. appearance of new outbreaks. ”

The disadvantage is that the first regions in Spain that started it lack important historical data about the early onset of the pandemic in Spain, while that history is important to correctly interpret the data collected in the wastewater. “If the levels rise or fall, we can already draw conclusions,” explains Villanueva. Comparisons can also be made between different moments when there were specific social consequences, such as a large number of people in hospital or a high death rate.

Interpretation of data complicated

According to Villanueva, the interpretation of the data is probably the most difficult part of this technique: “Sometimes we see a sharp increase in an area, but it turns out that there is a hospital there”. He also wants to combine this system with with the PCR test practice. “The analysis of wastewater is more extensive, no one is left, because everyone goes to the bathroom. The problem is that you never know the identity of those who are infected, only PCRs are sufficient for that,” explains Villanueva.

The companies taking the samples only pass the information on to politicians and the regional and national ministries of health. The national ministry is said to have told the newspaper El Confidencial that data about the sewage water has been requested from all autonomous communities. They have not yet indicated which regional authorities have already sent information or to what extent this could be alarming or what the detected parameters mean.


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