HYDERABAD: Around 6.6 lakh people in Hyderabad (around 6.6 percent of the total population) may have been infected with COVID-19 in just the last 35 days and at present, the city might be home to about 2.6 lakh active cases -- and these are just conservative estimates.
This has been revealed in a study by the Hyderabad-based Center for Cellular and Molecular Biology (CCMB) and Indian Institute of Chemical Technology (IICT), which conducted COVID-19 surveillance in the city by testing sewage samples collected from various Sewage Treatment Plants.
This finding highlights that the actual number of people infected by COVID-19 is many times higher than the number of cases being reported after people develop symptoms and get tested.
CCMB Director, Dr Rakesh Mishra, explained, “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 or mortality is way lower than otherwise expected with such large infection rates at a given time. It explains why our healthcare system has been able to handle reasonably well the situation during the pandemic."
He added, "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.”
The CCMB in a media release on Wednesday said that individuals who are infected by COVID-19 shed the virus not only through nasal and oral routes but also through faeces. This provides an opportunity to use sewage samples to estimate the spread of the infection in a given locality or area. Also, the virus samples in sewage are non-infectious, making it easier for conducting the study.
As an infected person can shed viral material in faecal samples for up to 35 days, the study on sewage samples gives an idea of the number of people that might have been infected in a period of little more than a month.
Researchers from the CCMB and IICT covered around 80 percent of the STPs in Greater Hyderabad Municipal Corporation limits and harvested sewage samples to estimate the number of potentially infected individuals in the city.
Sewage samples from the STPs were processed for detecting presence of the viral RNA of novel coronavirus. As the STPs in Hyderabad receive sewage from about 40 percent of the households, the findings were later extrapolated for the entire city.
They also found that while the viral RNA was detectable in the inlet samples of the STPs, the outlet (after treatment) samples were largely clean (free from viral RNA), indicating efficient treatment practices at STP.