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National Capital Delhi To Have Monthly Sero-surveys; Here Are The Findings Of Latest Sero-survey

To assess the prevalence of SARS-CoV-2 in the national capital Delhi, a sero-survey was conducted from June 27 to July 10; 21,387 samples were collected from all 11 districts

National Capital Delhi To Have Monthly Sero-surveys; Here Are The Findings Of Latest Sero-survey
  • 22.86 per cent prevalence of COVID-19 infection found in Delhi
  • Over 77% of the people surveyed remains susceptible to contracting COVID-19
  • Preventive and containment measures need to continue to avoid spike

New Delhi: Around 23 per cent of the 21,387 people surveyed in Delhi have been exposed to the Novel Coronavirus and has developed antibodies against the virus, states the findings of the sero-survey carried out by the National Centre for Disease Control (NCDC) in collaboration with the government of Delhi. According to the survey, a large number of infected people remain asymptomatic. The survey done to assess the prevalence of SARS-CoV-2 in the national capital studied 21,387 samples collected from all 11 districts of Delhi. The study was conducted from June 27 to July 10 which means the findings highlight the status of COVID-19 in Delhi during the third week of June, said Dr. V. K. Paul, Member (Health), NITI Aayog, during a media briefing.

Before we deep dive into the findings of the sero-survey and what it means in continuing the fight against COVID-19, let’s understand what is sero-survey, how and why is it done.

Also Read: As Recovery Rate In Delhi Follows An Upward Graph, A Look At Delhi’s Response To Coronavirus Outbreak

What Is Sero-Survey?

Blood serum of a group of individuals is tested to see if they had COVID-19 in the past. It is done to gauge the prevalence of the virus in that area. For the sero-survey, antibody test, also known as a serology test is done. It determines whether the human body had contracted COVID-19 in the past and now has antibodies to fight against the virus. It examines if an individual’s immune system – body’s defence against illness – has responded to the infection.

Antibody test is not a COVID-19 diagnostic test. It is typically done to see if someone has been exposed to the virus and checks the presence of these antibodies. In the case of COVID-19, over 98 per cent of patients develop antibodies, said Dr Rajesh Parikh, Director, Medical Research at Jaslok Hospital and Research Centre.

Also Read: Coronavirus Outbreak Explained: What Is Antibody Test And What Role Does It Play In The Fight Against COVID-19?

Blood samples are tested for detecting antibodies. There are two kinds of antibodies – IgM (Immunoglobulin M) and IgG (Immunoglobulin G). Explaining the two and how they help in detecting COVID-19, Dr S.K. Singh, Director of NCDC, said,

IgM antibody indicates the presence of active COVID-19 infection and starts getting positive after a week of contracting the virus. But since IgM disappears soon, it does not give a clear picture of total exposure. On the other hand, IgG antibody develops after two weeks of the onset of the infection and remains in the body for a sustained and longer period.

Further explaining the objective of conducting a sero-survey, Dr S.K. Singh said,

It is natural that some people such as asymptomatic people are missed by any surveillance network that is put in place. In this scenario, a sero-survey helps to assess the prevalence of COVID-19 infection in the community.

How Was Sero-Survey Conducted In Delhi?

Earlier, the Indian Council of Medical Research (ICMR) had undertaken sero-survey on the containment zones of Delhi. To assess the prevalence of COVID-19 in Delhi, on a larger scale, the recent survey was done by NCDC.

For antibody testing, indigenous test kit COVID KAVACH ELISA developed by the Indian Council of Medical Research-NIV Pune was used. The IgG ELISA test kit has a sensitivity rate of 92.1 per cent and specificity rate of 97.7 per cent. A high specificity rate means the test kit is less likely to give false positives.

Also Read: Indigenous ELISA Kits 92.37 Per Cent Sensitive, 97.9 Per Cent Specific For COVID-19 Testing: Indian Council of Medical Research

Findings Of Cross Sectional Sero-prevalence Study On SARS-CoV-2 Infection

The study found 22.86 per cent prevalence of COVID-19 infection in Delhi. Explaining the findings, Dr. Singh said,

23.48 per cent prevalence has been found but considering the sensitivity and specificity rate of the IgG ELISA test kit, the results have been adjusted and therefore, 22.86 per cent is the final finding.

Out of the 11 districts, eight districts have shown over 20 per cent prevalence of COVID-19. With 27.86 per cent, central district has topped the charts followed by North East district (27.7 per cent) and Shahdara (27.61 per cent). This specifies that in these areas, the spread of the virus is high.

However, maximum samples (3,548) were tested from North West district that has shown a prevalence of 23.31 per cent.

Sharing his interpretation of the research, Dr. V. K. Paul noted that there are two sides of a coin and said,

Even after six months, in a densely populated city like Delhi, the infection has reached only around 23 per cent. This points out that the measures taken by the government and community have helped contain the infection to this level. This gives us confidence in the effectiveness of the containment strategies taken.

Also Read: Delhi’s COVID-19 Recovery Rate Nearly 88 Per Cent; Delhi Government To Come Out With Economic Revival Plan

While talking to NDTV, Dr Rakesh Varma, Additional Directorate General of Health Services, Government of India shared the same opinion and said,

Delhi has got a dense population and the preventive strategy has worked in the national capital. It reiterates that measures like hand washing, social distancing need to be continued.

Dr Sandeep Budhiraja, Group Medical Director, Max Healthcare shared his opinion about the sero-survey and said there is both a good and bad side to this report. Explaining the two, Dr Budhiraja, said,

All people were asymptomatic this means that the disease in Delhi has been a mild disease. The majority of the people are asymptomatic, they probably have not even realised that they have recovered from COVID. However, the bad part is, an asymptomatic person who himself doesn’t know that he has infection has a higher potential and likelihood of spreading the infection to others. Hence, the need for strict testing at the time when you have an infection and to diagnose the infection, you need to go for RT-PCR or rapid antigen test.

The flip side of the finding reveals that over 77 per cent of the people surveyed are still vulnerable to contracting the disease. In a broader context, a large chunk of the population is susceptible to the disease which means we should not let our guards down anytime soon. This 77 per cent includes senior citizens, people with co-morbidities and other members of the vulnerable group. Hence, precautionary measures like social distancing, wearing a face mask, and hand hygiene need to be practised well.

Also Read: COVID Cases Seem To Have Hit Peak In Delhi, Cases On Decline Now: AIIMS Director Dr Randeep Guleria

According to Dr Budhiraja, the downfall in the fresh COVID-19 infections and the survey doesn’t mean that we can relax. The citizens need to remember that still over 75 per cent of the population remains uninfected or presently infected but not immune because they have not developed the antibody response and we are already 6 months down the pandemic. He said,

Clearly the peak seems to be in the past now but at this stage, 75 per cent of the population is still vulnerable so we must not let our guards down. If we do that, this vulnerable population can again fall prey and we may not have one or two spikes but multiple spikes.


The national capital Delhi is among the worst-hit states in terms of COVID-19 infections but has an exemplary recovery rate of over 84 per cent. Delhi has recorded over 1.25 lakh COVID-19 cases of which over 1.06 lakh patients have recovered from the contagious disease. The daily growth in COVID-19 infections has gone down. On July 21, for the first time in seven weeks, Delhi recorded less than 1,000 fresh cases.

Keeping up with its fight against COVID-19, the state government has decided to conduct sero-surveillance every month. Speaking at a press conference, Delhi Health Minister Satyendar Jain informed,

It will be done from the 1st till 5th of every month so that we can know how many people have been infected.

Also Read: Health Minister Satyendar Jain Explains Delhi’s Model Against Coronavirus, Shares His Experience Of Battling The Disease

NDTV – Dettol Banega Swasth India campaign is an extension of the five-year-old Banega Swachh India initiative helmed by Campaign Ambassador Amitabh Bachchan. It aims to spread awareness about critical health issues facing the country. In wake of the current COVID-19 pandemic, the need for WASH (WaterSanitation and Hygiene) is reaffirmed as handwashing is one of the ways to prevent Coronavirus infection and other diseases. The campaign highlights the importance of nutrition and healthcare for women and children to prevent maternal and child mortality, fight malnutrition, stunting, wasting, anaemia and disease prevention through vaccines. Importance of programmes like Public Distribution System (PDS), Mid-day Meal Scheme, POSHAN Abhiyan and the role of Aganwadis and ASHA workers are also covered. Only a Swachh or clean India where toilets are used and open defecation free (ODF) status achieved as part of the Swachh Bharat Abhiyan launched by Prime Minister Narendra Modi in 2014, can eradicate diseases like diahorrea and become a Swasth or healthy India. The campaign will continue to cover issues like air pollutionwaste managementplastic banmanual scavenging and sanitation workers and menstrual hygiene

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