NEW DELHI: A day after announcing a hospital-based survey to test 200 persons every week in all 733 districts to check for exposure to Covid-19 virus, the Centre on Tuesday said another a household survey will be conducted simultaneously in 69 districts across 21 states to assess the spread of the infection in the country.
The latest plan involves covering 24,000 adults distributed equally across four strata of districts categorized on the basis of reported cases of COVID-19 through which venous blood samples from 400 randomly selected individuals (one per household) from 10 clusters in each district will be tested for SARS CoV-2 antibodies.
The highest 9 districts chosen for this survey, meant to assess the extent of community transmission, are in Uttar Pradesh, followed by 6 districts each in Maharashtra, Bihar and West Bengal.
The project will be carried out by the Indian Council of Medical Research, the National Centre for Disease Control and World Health Organisation along with state health departments using the ELISA antibody test recently developed by the National Institute of Virology, Pune.
For this, help is also being taken for tuberculosis staffers--which means that an ongoing national TB survey will be put on hold.
“The results of the survey will provide information about the spread of SARS-CoV-2 infection in different parts of the country,” said an official in the ministry.
Experts pointed out that it looks like a robust design but the key would be in implementation as per the protocol.
“While this study would definitely contribute to understanding the transmission dynamics, existing lab-linked surveillance such as IDSP data can provide a comprehensive national overview,” said Dr Oommen John, public health specialist attached with the George Institute of Global Health in New Delhi.
The government on Monday had said that 200 samples will be collected from 10 health facilities -- 6 government and 4 private -- every week to test for the presence of virus or its antibodies in people who might have recovered.
As per this plan, the samples are to be collected from 100 healthcare workers -- categorized as high-risk population, 50 out-door patients without influenza-like symptoms and 50 pregnant women visiting hospitals -- categorized as low-risk population using both RTPCR and ELISA tests.
Some scientists, meanwhile, have expressed concern that the ELISA test developed by NIV Pune could show way too many false negative and false positives given its 92 per cent sensitivity and 97 per cent specificity.
“This test will be reliable in areas with low infection prevalence but might give a false picture in districts with 10-12 per cent overall infection rate,” said a top government virologist requesting anonymity.