Highlights

  • An infected person shed viral material in faeces for up to 47 days since the symptom onset and remains infectious till 14 days since symptom onset.
  • About 6.6% of Hyderabad’s population is infected which clearly indicates the rate of community transmission and asymptomatic carriers is higher than the number of reported cases: CCMB
  • The monitoring of SARS-CoV-2 in wastewater could quantify the scale of infection prevailing among the community with a benefit of detecting virus from symptomatic, asymptomatic, or pre-symptomatic cases which manifest as an early-warning sign: CCMB

 

Hyderabad: Researchers at the Center for Cellular and Molecular Biology, studied the sewerage water samples collected across the twin cities and concluded that 6.6 lakh people are COVID infected. This includes symptomatic, a  majority of asymtomatic and those recovered.

The study  indicates the rate of community transmission and asymptomatic carriers is higher than the number of reported cases. Every 2nd person in 5 are or were infected in Hyderabad.

As part of the study, RT-PCR based detection of SARS-CoV-2 RNA was used for screening the inlet water in the
Sewage Treatment Plants (STPs) that cover about 80% of Hyderabad’s STP capacity. Researchers found that SARS-CoV-2 RNA was detected in the inlets of all the tested STPs  indicating that the infection is widespread.

What method did CCMB use to calculate the number of infected?  

The study that lasted for 35 days beginning 7 of July, took  into account the number of RNA copies present in the
wastewater and the number of RNA copies present in the faecal matter of infected individuals. “Our data indicates that approximately 6.57% of Hyderabad’s population is infected during the window of 35 days.  Existing reports suggest that an infected person shed viral material in faeces for up to 47 days since the symptom onset and remains infectious till 14 days since symptom onset”.

The data indicated that, every  2 in 5 infected people are infectious at any given point of time during the 35 days window. Approximately 2.6% of the total population of Hyderabad are potentially infectious during the study period.

A total of 30 samples were collected from 14 inlets and 14 treated outlets of 10 STPs and 2 samples from a gated community.

Table: Extrapolation of CCMB’s data shows the total number of infected and potentially active people in the city of Hyderabad.

  1. Capacity of STP covered (MLD):  603.5 MLD
  2. Average no. of infected people during the window (07-July  to 08-August- 2020)–220343
  3. Total STP capacity of Hyderabad (MLD)- 772
  4. Number of infected (extrapolating to total STP capacity)- 281864
  5. Total wastewater generated in Hyderabad (MLD)- 1800
  6. Number of infected (extrapolating to entire population)- 657197
  7. Population of Hyderabad- 10004144
  8. % Virus shedding individuals- 6.57%
  9. Fraction of active cases in the population- 0.4 %
  10. Number of individuals in potentially active phase of infection- 262878

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