About 6 lakh of Hyderabad’s population could have been infected with the COVID-19 virus including symptomatic, asymptomatic, and also recently recovered individuals in a time window of about 35 days.
This is according to a joint study taken up by CSIR institutions of Centre for Cellular & Molecular Biology (CCMB) and Indian Institute of Chemical Technology (IICT) after harvesting the sewage samples to estimate the number of potentially infected individuals in the city.
Individuals infected by SARS-CoV-2 shed virus not only through nasal and oral routes but also through faeces and hence, provides an opportunity to use sewage/wastewater samples to estimate the spread of the infection in a given locality or area. SARS-CoV-2 in sewage samples is non-infectious, thus making sewage samples suitable for epidemiological studies, said CCMB Director Rakesh Mishra on Wednesday.
Sewage samples from major STPs were processed for detecting the presence of SARS-CoV-2 viral RNA. While viral RNA is detectable in the inlet samples, the outlet (after treatment) samples of STP were largely clean (free from viral RNA) in this regard, indicating efficient treatment practices at STP.
The study covers about 80% of STPs revealed that there are around 2 lakh people shedding viral materials. The findings are posted on preprint server, MedRxiv, which is yet to be peer reviewed.
“Our finding clearly indicates that a large proportion of the affected individuals are asymptomatic and did not need hospitalization. This is also in agreement with the observation that hospitalization rush or mortality is way lower than otherwise expected with such a large infection rates at a given time. It explains why our healthcare system has been able handle reasonably well the situation during the pandemic. Such studies if carried out in coordination with civic bodies to identify the hotspots in the city and monitor the dynamics of the infection rate can assist the system in taking necessary measures”, explained Dr. Mishra.
Estimating the spread is very important in identifying the affected areas, and controlling the pandemic. Since an infected person sheds viral material in faecal samples for up to 35 days, these studies will provide an overall estimate of the situation in a window of one month.
All the experiments were conducted at the CSIR-CCMB COVID-19 testing facility and the teams included Hemalatha Manupati, Kopperi Harishankar and S.Venkata Mohan from CSIR-IICT and Uday Kiran, C.G. Gokulan, Santosh Kumar Kuncha and Rakesh K Mishra from CSIR-CCMB, he added.