Wastewater reprocessing basin. (Drawing) – A. GELEBART / 20 MINUTES
- In one of its latest reports, the Obépine network, the Epidemiological Observatory in Wastewater, showed a still high presence of Covid-19 in the waters of the Toulouse-Ginestous wastewater treatment plant.
- At the same time, other indicators of virus circulation, in particular the positivity rate of PCR tests or hospitalization, show a drop in the number of cases in the Pink City.
- According to Toulouse virologist Jacques Izopet, these indicators, with different timing, are not contradictory, but show that the virus continues to circulate but in a “non-worrying” manner.
For several weeks, the health authorities have observed a drop in the number of Covid-19 cases in Toulouse, as in the whole of France. A trend which is reflected in a drop in hospitalizations for serious cases which is explained, in particular, by the increase in the number of people vaccinated.
Figures that suggest that the virus is circulating less. But an indicator could suggest that it is not. Indeed, the latest figures published a week ago by the Obépine network (Epidemiological Observatory in Wastewater) show a concentration of the virus in the wastewater of the Toulouse-Ginestous treatment plant is at fairly high levels.
“The level of circulation of the virus is quite high”, indicates the research consortium created last year to analyze wastewater and detect possible traces of Covid-19 in order to anticipate, among other things, a rebound in the circulation.
Updated this Friday, these figures show that the level remains fairly high, but is starting to decrease, but remains above the average recorded in Occitania. On other Haute-Garonne resorts, managed by the
joint water and sanitation union Network 31 which also publishes Covid-19 monitoring indicators, on May 21, ten of the thirteen stations tested showed the presence of viral loads. With a more active circulation in the waste water of Castelnau d’Estretefonds.
Different timing
“The virus probably circulates less, the impact is less on severe forms, nevertheless it continues to circulate. The fact that we have several indicators means that we approach things from different angles. The PCR incidence and positivity rate figures are very fine indicators. But depending on the period, we can have a greater or lesser number of people who are tested. On the eve of holidays or long weekends, many people who had no symptoms and were not in contact have resorted to it. The positivity rate of the tests is found to be biased in a way, ”explains Jacques Izopet, head of the virology laboratory at the CHU Purpan, in Toulouse.
On Tuesday, in its last bulletin, the Regional Health Agency indicated that during the past week, out of 240,000 PCR tests carried out in Occitanie, only 2.6% came back positive, when it was 8.5% a month earlier.
“The interest of researching the virus in the waters is that there is no a priori. We will capture all infected people, regardless of strategies and periods leading to variations in the number of periods that will be tested. It was said that the search for the virus in the waters could anticipate the spread of the virus to the entire population by a few days. It is not the same timing “, continues the virologist, for whom the trend is not however” worrying at this stage “.
This presence in wastewater certainly also reflects a low noise circulation of the virus among a younger, unvaccinated, and asymptomatic population. “This is the reason why we will eventually vaccinate young people, it will be a good measure to accelerate the circulation of the virus”, concludes Professor Izopet.