Delhi Health Minister Satyendar Jain said the national capital's next round of monthly sero-prevalence survey began on Tuesday covering all 272 municipal wards to analyse the Covid-19 situation in Delhi at "micro-level". The sample size this time will be 17,000 and the exercise will be carried out for seven days, he told reporters. The last sero-prevalence survey was held from August 1-7, which showed that 29.1 per cent of the people surveyed had anti-bodies against the coronavirus infection.