Here is all you need to know about the serological survey:1) Delhi will conduct serological test of 20,000 samples from June 27 till 10 July2) This will help in comprehensive assessment of the spread of infection in Delhi and will help draw up a comprehensive strategy.3) The sero-surveillance study will be conducted in all 11 districts of Delhi on a random basis including individuals below 18 years of age.4) Serology (antibody) tests are largely used for surveillance among the community.5) They can be used on people who have already been tested positive for the virus or even those who are asymptomatic, and can reveal insights on immunity against Covid-19.Meanwhile, India's Covid-19 tally raced past five lakh today with the highest.