With more than 18 lakh Covid cases reported so far in India, the rate of transmission in major cities, including Delhi, Mumbai and Chennai, has dropped down to below 1, Indian Express reported.

The decrease in the reproduction number or transmission rate indicates the beginning of the end of a pandemic.

According to Sitabhra Sinha, an official at the Institute of Mathematical Sciences in Chennai, a large part of the population seems to have developed immunity against the virus if the R-value goes below 1.

However, in the case of Delhi, Sinha said there was still a large uninfected population and “potential victims of the virus”.

Last week, the R-values in Mumbai and Chennai plummeted below 1.

In Delhi, the R-value had gone below 1 for the first time in the second week of July. Between July 23 and 26, the R-value for Delhi was 0.66.

Meanwhile, Delhi has initiated sero-prevalence survey on Saturday, which will run for a week. The survey will analyse the blood serum levels of individuals to see the presence of antibodies against the virus, as per media reports.

The previous survey had revealed that almost 24 per cent of the sampled Delhites had developed antibodies, which means they have got infected and recovered.