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A szennyvíz alapú epidemiológia jelentősége a COVID–19 járványban és azon túl

The importance of wastewater-based epidemiology in the COVID-19 pandemic and beyond

Scientia et Securitas
Authors: Tamás Pándics, Eszter Róka, Bernadett Khayer, Zoltán Kis, Luca Bella Kovács, Nóra Magyar, Tibor Málnási, Orsolya Oravecz, Bernadett Pályi, Eszter Schuler, and Márta Vargha

Összefoglaló. A szennyvízalapú epidemiológia módszere a jelenlegi világjárványban egyre inkább előtérbe kerül. Mivel a szennyvízhálózatot szinte mindenki használja, ezzel a módszerrel gyorsan és olcsón lehet reprezentatív egészségügyi információhoz jutni, az így keletkező adatok pedig támogatást és visszajelzést nyújthatnak a döntéshozatalban. A Nemzeti Népegészségügyi Központ 2020 júniusa óta működteti a COVID–19 előrejelző rendszert. A mintavételek hetente történnek Budapest három szennyvíztisztítójából, valamint a megyeszékhelyekről. A kapott adatok hazánkban is előrejelzik az esetszám alakulását, az eredmények gyors kommunikációja pedig lehetővé teszi a járványhelyzetre történő felkészülést. A szennyvízalapú epidemiológia alkalmazása a jövőben más területeken is megfontolandó hazánkban is.

Summary. Wastewater based epidemiology (WBE) is an emerging method in the current COVID-19 pandemic. Since almost everyone uses the sewerage system, wastewater is technically a composite sample representing the entire population of the area serviced by a wastewater plant. This community sample contains pathogens and compounds excreted by the human body through feces or urine, and can be used to obtain information on the health status of the community. It was successfully used previously for confirming the eradication of poliovirus and tracking legal and illegal drug consumption.

The etiological agent of COVID-19, the SARS-CoV-2 virus is an enveloped, single strand RNA coronavirus. Although it is a respiratory virus, it is also shed in feces both in symptomatic and asymptomatic infections. Wastewater therefore can be used to estimate outbreak trends and support outbreak management.

Wastewater monitoring efforts in Hungary started in June 2020, first in Budapest, then gradually extended to a national surveillance system. Weekly samples are collected in the three wastewater treatment plants servicing Budapest, and from every county seat. The analyzed 22 samples represent approximately 40 % of the population. Raw sewage samples are centrifuged to remove the debris and concentrated by membrane ultrafiltration. RNA is extracted from the concentrate and SARS-CoV-2 is quantified by RT-qPCR. Results are normalized to Enterococcus counts to correct for the bias of dilution from precipitation.

The first results in June reflected the decline of the first wave of the outbreak. During the summer, viral RNA concentrations were low, mainly below the limit of detection. The increase of RNA in the sewage preceded the resurge of cases by 2 weeks. Trends of viral concentration followed the same pattern as the number of infections in the second and third wave. SARS-CoV in sewage shows statistically significant association with the number of new cases in the following weeks, thus it can be used as an early warning system.

Results are communicated weekly to the governance board responsible for outbreak management, or more frequently in case of outstanding results or when it is necessary for decision support. Weekly information is also made available to the public. To inform the public, concentration categories (low, medium, elevated and high) were defined, representing orders of magnitude of the viral RNA concentration. Trends (increasing, stagnating or decreasing) are also indicated.

The establishment of a long-term wastewater surveillance system would provide an opportunity for early recognition of future emerging infections, tracking seasonal influenza, drug use or even the detection of certain bioterror attacks. It would be an important addition to maintaining the health and safety of the Hungarian population.

Open access