A szennyvíz alapú epidemiológia jelentősége a COVID–19 járványban és azon túl
Authors: Pándics Tamás , Róka Eszter , Khayer Bernadett , Kis Zoltán , Kovács Luca Bella , Magyar Nóra , Málnási Tibor , Oravecz Orsolya , Pályi Bernadett , Schuler Eszter , Vargha Márta 
Published: October 2021

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.