All you need to know about the serological survey being conducted in Delhi

New Delhi, June 27: A mammoth campaign begins in Delhi today to determine the spread of the coronavirus disease.

The serological test or the sero surveillance study is part of the COVID-10 response plan which has been prepared by the Centre for Delhi. Delhi has reported 73,780 cases of coronavirus and 2,429 deaths.

So, what is a serological survey: Here is what you should know:

Serological tests are used to identify antibodies, which are created by the immune system when someone is infected with the virus, and antigens in the blood. The test can be conducted to diagnose infections and autoimmune illnesses. It can also be conducted to check if a person has immunity to certain diseases.

The serology of anti-body tests are largely used for surveillance among the communities. It can be used on people who have already tested positive for the virus or even those who are asymptotic.

These surveys are used to determine who has antibodies and find out who has been infected with the virus. It can also be used even if someone never tested positive or experienced symptoms.

The serological survey will be done throughout Delhi between June 27 and July 10. This would enable authorities to undertake a comprehensive analysis of COVID-19 and then prepare a broad strategy to combat the spread of the virus in Delhi.

The survey will be conducted by the National Centre for Disease Control and the Delhi Government. The focus would be on the anti-body based blood tests to find out residents' past exposure to the Sars-Cov-2 virus which caused COVID-19.

The tests will be conducted in all the 11 districts of Delhi focusing on at least 20,000 households on a random basis. It would also be conducted on individuals below the age of 18.

The survey includes IgG Enzyme Linked Immunosorbent Assay (ELISA) test and it estimates the proportion of the population exposed to the Sars-Cov-2 infection. This is however not useful for detecting acute infections. It however indicates episodes of infections that have happened in the past. The test is approved by the ICMR due to the high sensitivity and specificity.

Five millilitres of blood sample is collected from the individuals. It is then put in a machine where the blood and plasma are separated. The plasma is then used to detect antibodies developed against COVID-19 in the body.

It may be recalled that in May the ICMR had conducted a pilot sear survey across 83 districts in 21 states. The result showed that the percentage of general population to have been identified in the past was 0.73 per cent. The urban areas had shown higher prevalence of the virus of around 1.09 per cent.

On Friday, the Spokesperson of the Union Home Ministry had tweeted, "as per the directives of HM @AmitShah, discussion was done on the serological survey in Delhi, which will be carried out jointly by NCDC and Delhi Government. Survey will begin from June 27, training of all the concerned survey teams was completed yesterday."