By Cyril Dela Rosa
Since the beginning of the COVID-19 pandemic, many different metrics and methods have been used as a means to monitor the spread of the virus. While a respiratory virus is found to often be spread by airborne transmission, novel methods have been achieved by the Chicago Department of Public Health (CDPH) to keep track of COVID-19 infection rates by studying its presence in the municipal water treatment system.
This CDPH-sponsored research is conducted through support from research institutions like the University of Illinois and by using the infrastructure of the Metropolitan Water Reclamation District of Greater Chicago (MWRD). The latter is the city’s primary wastewater management system that treats around 1.2 billion gallons of sewage each day at its seven water reclamation plants across Cook County. 24-hour composite samples are retrieved from these plants that can monitor the levels of severe acute respiratory syndrome coronavirus (SARS-CoV, or more specifically SARS-CoV-2 as the second virus strain to be recorded), the virus which causes the COVID-19 disease.
In measuring the levels of virus strain levels found within wastewater originating from catchment areas of Greater Chicago, data has been generated to represent where more SARS-CoV-2 has been found across the MWRD operating plants. As of Dec. 2021, the CDPH had successfully shown strong correlations between wastewater surveillance data and the surge of total COVID-19 cases during the introduction of the Omicron variant. The CDPH also successfully identified the Omicron variant within wastewater samples before this mutation of the virus became the dominant variant causing COVID-19 cases in Chicago.