Thread by @ccmb_csir

#longthread
With @csiriict we did a study from 10 Sewage Treatment Plants (STP) and a gated community in Hyderabad to look for SARS-CoV-2 RNA. These STPs get 40% of sewage in the city. We estimated viral load in those samples using RT-PCR.
ccmb.res.in/presscovrg/Was…
@CSIR_IND
1/n

Feces are known to contain non-infectious RNA copies of the coronavirus.
pubmed.ncbi.nlm.nih.gov/26246784/
Sewage treatment plants that get samples from a huge part of a city become good candidates for checking for the viral RNA from many people together.
2/n

We estimated viral load in those samples using RT-PCR. We estimated the number of people shedding the virus using calculation methods and data from previously peer-reviewed published work. Some of the key reviews are: sciencedirect.com/science/articl…
sciencedirect.com/science/articl…
3/n

Our calculations rely on 2 methods:
Method 1: (Ahmed et al., 2020)
No of infected individuals=((RNA copies/L water)*(L water/day)) / ((g feces/day)*(RNA copies/g feces) )
Feces excreted/person/day on an avg = 128g
One positive person sheds an avg of 10^7 RNA copies/g of feces
4/n

Method 2: (Hellmér et al., 2014)
No of infected individuals=No of RNA copies per litre of waste water/No of RNA copies per person to total sewage water

Avg RNA copies excreted per person = 1.2×10^9
5/n

With all of these, we find that at least 6 lac people, i.e. 6% of the population of Hyderabad are infected with the SARS-CoV-2. This includes those with symptoms, asymptomatic individuals and those who recovered in the last 35 days.
The study is submitted to @medrxivpreprint
Fin