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Exponential dispersion of the Omicron strain of SARS-CoV-2 in the community of Thessaloniki but also the maintenance of the Delta strain load show the latest measurements of the Wastewater Epidemiology Group of the Aristotle University of Thessaloniki in the city's municipal wastewater.
Analyses of daily wastewater samples taken between 19/12 and 29/12 show that the viral load of the Omicron strain doubles every 1.86 days.
Overall, as shown in the charts presented by APPE-ME, within 10 days, the incidence of Omicron increased from 3.5% to 60.3% of all detectable strains. However, the comparison of the total viral load with that of Omicron shows that the spread of Delta does not decrease from 19/12 onwards. This, as the members of the AUTH team point out, is a point of concern, as the Delta strain is more infectious and is responsible for a significant burden on the health system in the period before the emergence of Omicron, and in particular in the month of November.
The average of the two most recent measurements, i.e. Tuesday 28/12 and Wednesday 29/12, is:
-Very high (+87%) compared to the average of the two immediately preceding measurements, Sunday 26/12 and Monday 27/12.
-Very high (+183%) compared to the average of the previous Tuesday 21/12 and Wednesday 22/12.
"The Omicron pandemic wave arrived in the city before the health system had even decompressed, as the Delta strain still has a significant spread and is driving vulnerable groups and unvaccinated people to hospitals. Even if the international data and predictions so far confirmed that the prevalence of the Omicron strain is characterised by many cases but few hospitalisations, there is still a large number of unvaccinated people. These citizens, especially if they belong to vulnerable groups, being almost certainly infected, are not protected against severe disease. If at the same time the admissions of people infected from the Delta continue, the city's hospitals will be under pressure, which may intensify as the high contagiousness of Omicron and the vaccinated will not leave the health personnel unaffected, a percentage of which will necessarily go out of service in quarantine, "said the rector of the Aristotle University of Thessaloniki and scientific leader of the research project, Professor Nikos Papaioannou.
"The best we can do at the moment is to limit our movements and contacts to a minimum and completely avoid any contact with people belonging to vulnerable groups. At tonight's and tomorrow's family and friends' gatherings, everyone should protect their neighbours and undergo a self-diagnostic or rapid test before coming into contact with other people," he said.
"In recent days there has been a huge increase in cases among young people and children. Whether the new mutation causes more gastrointestinal manifestations and greater viral load in the stools of infected persons with greater excretion and concentration in city sewage remains to be proven," said Professor of Pediatric Infectious Diseases at the Aristotle University of Thessaloniki Emmanuel Roilides.
"The evolution of Omicron spread in Thessaloniki"
"In the period 18 to 22/12, when the Delta strain was still dominant, the model of the wastewater epidemiology team of the AUTH estimated that the number of unrecorded cases (asymptomatic etc.) was similar to the number of cases recorded by EODY. The estimate for that period showed about 57,000 total infected persons. Since then, however, the picture has changed dramatically as there has been a progressive prevalence of the Omicron strain, for which little is known about the viral load distribution of cases on days of illness. Based on the little information in the international literature, the viral load of Omicron cases may be up to 1000 times higher than that of Delta and the development of infection in them about 70 times faster. These new Omicron data are already being run in the AUTh model but data from a few more days are needed to ensure the statistical significance and reliability of the estimates," said AUTh chemistry professor Thodoris Karapantsios.
"Since the emergence of Omicron, the actual number of cases is higher than that recorded by the surveillance system as the majority of infections involve young and/or vaccinated people who do not show symptoms. Also, infections in these individuals cannot be captured by genomic surveillance as the sampling there is mainly of people with a clinical picture. Based on the above and the fact that wastewater analyses are representative of the community as a whole and are now done rapidly, we believe that only wastewater can show a more representative picture of the evolution of the spread and its rate in real time," explained Chrysostomos Dovas, Associate Professor of Molecular Microbiology at the Department of Veterinary Medicine, Aristotle University of Thessaloniki.
"During the last week there were some changes in the physical and chemical characteristics of the wastewater mainly due to population fluctuations in the service area of the WWTP and sporadic rainfall in Thessaloniki. These changes did not affect the quantification of the viral load, but were taken into account during the rationalisation phase of the measurements", explained the head of the wastewater reception team of the Laboratory of Environmental Engineering and Design of the Department of Civil Engineering of the Aristotle University of Thessaloniki.
Source: protothema.gr
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