There may be at least six lakh people in Hyderabad who have been infected by coronavirus, a large number of them asymptomatic, a study said on Wednesday.
A study by CSIR-Centre for Cellular and Molecular Biology (CCMB) and CSIR-Indian Institute of Chemical Technology has said individuals infected by SARS-CoV-2 shed virus not only through nasal and oral routes but also through faeces.
Scientists of both institutes collected sewage samples from 18 of the 23 sewage treatment plants (STPs) in Hyderabad to estimate the number of people who may have been infected. “Based on our study, we can say that at least 2 lakh people are infected in Hyderabad alone,’’ said CCMB Director Dr Rakesh Mishra.
“The study covers about 80 per cent of the STPs in the city but only about 40 per cent of the Hyderabad sewage reaches STPs, and if this data can be used to extrapolate, the overall number of potentially infected people turned out to be approximately 6 lakh that is around 6 per cent of the the city’s population, which includes symptomatic, asymptomatic, and also recently recovered individuals in a time window of about 35 days,” he said.
The SARS-CoV-2 in sewage samples is non-infectious, thus making them suitable for epidemiological studies.
The findings are posted on preprint server MedRxiv, which is yet to be peer reviewed, said Dr Mishra.
As of August 16, 75,600 cases have been reported in Greater Hyderabad Municipal corporation areas.
Health Minister Etela Rajender said he has asked officials to go through the study. “I have asked senior officials to look into it. I cannot say if so many people are infected in the city as of now. We have increased testing already,’’ he said.
“Our findings clearly indicate that a large proportion of the affected individuals are asymptomatic and did not need hospitalisation,” Dr Mishra said.
“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,” he added.
Of the 1,800 million litres water used daily in Hyderabad, only 40 per cent is processed at STPs. For this study, 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 samples of STP were largely free from viral RNA, indicating efficient treatment, the study stated.