Coronavirus | ICMR completes second sero-survey

The first survey was conducted in May across 400 districts to gauge the spread of infection

Health workers take blood sample for a serological survey. File

The Indian Council of Medical Research has completed its second national sero-survey to gauge the prevalence of COVID-19. The first survey was conducted in May across 400 districts and about 28,000 were sampled — most of them in rural India — to gauge the spread of the infection. After a long delay, the ICMR finally published its results this month that suggested that nearly 6.4 million were likely infected with the virus by May. There were 82-130 infections that went undetected for every confirmed case in May.

However, newspaper reports on Sunday, citing unnamed authors of that study, alleged that a portion of their results were expunged, which showed high prevalence of the infection in hotspots in 10 cities that were originally part of the paper. This suggested that in May the possible prevalence of the infection was 36% in Dharavi, Mumbai; 48% in Ahmedabad and 30% in Calcutta.

 

These findings undermined the effectiveness of the lockdown in containing the spread of the virus and the government’s insistence that abrupt shutdown of the country had restricted the virus transmission to only a few dense urban agglomerations. The government also emphasises that there is, as of today, no evidence of community transmission in India.

“Containment zones, that refer to a specific geographical area where positive cases are found are dynamic in nature. They do not fit into nationally representative sampling,” the ICMR tweeted on Sunday evening but didn’t refer to the newspaper reports. “The second round of countrywide sero-survey led by ICMR has been successfully completed. The final phase analysis of the survey is now under way and will offer a comparison with the results of the first survey.”

The objective

Before it embarked on its national survey, the ICMR had explicitly specified that the survey’s objective was to estimate national prevalence and spread in hotspots. “The study has two parts out of which the primary task of estimating the fraction of population who has been infected with SARS-CoV-2 in general population has been completed. The second objective of estimating fraction of population who has been infected in containment zones of hotspot cities is in the process of completion,” the Health Ministry said in a statement on June 11, available on the website of the Press Information Bureau. On that day, Balram Bhargava, Director-General, ICMR, had said the prevalence of the disease was 0.73% nationally and that compared to rural areas, risk of spread was 1.09 times higher in urban areas and 1.89 times higher in urban slums.