Sero survey Delhi

EDITOR:The survey was conducted between 27 June and 10 July 2020. 21,387 samples were collected from 11 districts. Why? - To test for the presence of antibiotics in the general population.The survey reported that the prevalence of IgG antibodies is 23.48 %.

What is a serological survey?

An exercise to check the prevalence of the disease in a population by detecting the presence of specific antibodies against the virus. Since it is not possible to test everyone in the population, serological studies are used as a tool to assess the extent of disease spread in the community. A serological test is usually performed to diagnose infections and autoimmune illnesses. It can also be 

conducted to check if a person has developed immunity to certain diseases.

Which test was used?

The Delhi survey included the IgG Enzyme-Linked Immunosorbent Assay (ELISA) test

The test has been approved by ICMR.

What is the Importance of Sero surveys?

Because infected people can have mild illness or may not get medical care or testing, sero survey can be used to estimate the number of people who have been previously infected with SARS-CoV-2 and were not included in official case counts. An advantage of this test is that it can capture people who may have been asymptomatic and didn’t know they were sick. 

Implications 

About a quarter of Delhi’s population (48 Lakh) has been exposed to SARS COV 2** 

As IgG antibodies against the virus appear typically three weeks after the infection, sero-survey would have given the disease spread status till Mid June (40-50k cases).

Are the people having antibodies immune to the virus now?

It is not known yet if having antibodies to the virus that causes COVID-19 can protect someone from getting infected again, or, if they do, how long this protection might last.

Other Sero Surveys 

The Indian Council of Medical Research (ICMR) had earlier conducted a pilot sero- survey in April  across83 districts in 21 states. The initial results, which are being peer-reviewed, showed that the percentage of the general population to have been infected in the past was 0.73%, with urban areas having shown higher Covid-19 prevalence of about 1.09%. Even in some of the hardest-hit cities in the world,the studies suggest, the vast majority of people still remain vulnerable to the virus.In New York City, which has had the largest coronavirus outbreak in the United States, around 20 % of the city’s residents have been infected by the virus as of early May 2020.

Is Delhi on the path to achieve Herd 

Immunity?

NO

The herd immunity threshold for this new disease is still uncertain, but many epidemiologists believe it will be reached when between 60 percent and 80 percent of the population has been infected and

develops resistance.

What is the catch?

All estimates of herd immunity assume that a past infection will protect people from becoming sick a second time. There is suggestive evidence that people do achieve immunity to the coronavirus, but it is not yet certain whether that is true in all cases; how robust the immunity may be; or how long it will last.

MoHFW warning 

The Ministry has said that results show that a significant proportion of the population is still vulnerable to contracting the novel coronavirus infection. “Containment measures need to continue with the same rigour. Non pharmacological interventions such as physical distancing, use of face mask/cover, hand hygiene, cough etiquette and avoidance of crowded places etc. must be followed strictly’’