ICMR sero-survey results on spread of Covid-19 by early next week

Study to guide policymakers as India unlocks

In what can be a crucial aid to strategy making for easing the lockdown curbs across the country, the results of the serological survey conducted by the country's apex health research body is expected early next week. 

Meanwhile, the ICMR has also advised states to conduct periodical serosurveys to assess the spread of infection and also include high-risk individuals like policemen, frontline workers etc in it. 

Sero-survey means test of blood serum from a group of individuals to test sero-prevalence of something (antibodies for the novel coronavirus in this case). 

The household-level cross-sectional survey will cover 69 districts in 21 states. Sero-surveys help to understand the proportion of the population exposed to SARS-CoV-2 infection including asymptomatic individuals and depending on the level of sero-prevalence of infection, appropriate public health interventions can be planned and implemented for prevention and control of the disease. The Indian Council of Medical Research had initiated the survey in May. 

Speaking to Business Standard, Manoj Murhekar, director of the National Institute of Epidemiology (NIE), an ICMR institute that is coordinating the sero-survey said that the results can be expected by early next week. "It will tell us how far the infection has spread. This is a nation-wide survey where over 34,000 samples have been tested," he said. 

He added that data from West Bengal may not be included when the results are published as the state was hit by a severe cyclone which delayed the data collection. "West Bengal has started collecting the data and we will update the survey results once the data comes in,"Murhekar said. 

The survey will involve the collection of blood samples from 400 randomly selected individuals (one per household) from 10 clusters in each district. The blood serum from these individuals will be tested for the presence of the IgG antibodies using the ELISA test developed by the National Institute of Virology, Pune. Zydus Cadila has supplied the kits for the survey. 

IgG antibodies generally start appearing after two weeks of the onset of infection, once the individual has recovered after infection and last for several months. Therefore, the IgG test is not useful for detecting acute infection but indicates an episode of SARS-CoV-2 infection in the past. 

ICMR is conducting the survey in collaboration with the health ministry, National Centre for Disease Control, state health departments and key stakeholders (like the World Health Organisation). The survey is coordinated by NIE and the National Institute of Research in Tuberculosis (NIRT), Chennai. Besides this community-based survey, the Ministry of Health is also initiating hospital-based surveillance to monitor the trend of infection in all districts. 

In end of May ICMR also advised that state governments take up periodical sero surveys to assess the spread of infection in the population that would help to guide policymakers. 

The survey has been recommended for high risk or vulnerable populations (health care workers, frontline workers, immune-compromised individuals, individuals in containment zones, etc) to know who has been infected in the past and has now recovered. In an attempt to decide the future course of action against the pandemic, ICMR has communicated a detailed plan to all the states to measure coronavirus exposure in the general population as well as in high-risk populations.