NEW DELHI: The two most populous cities in India, Mumbai and Delhi, followed almost similar Covid-19 trajectories when the devastating second wave caught the country unawares, but the following weeks in these cities have thrown an epidemiological mystery with more questions than answers.
The fall in daily cases in Delhi, which hit a peak on April 24 with 25,555 cases detected in a day, has been far more dramatic and steeper as compared to Mumbai, which saw a peak on April 9 with 9,831 cases.
As on Friday, Mumbai had 10,608 active Covid-19 cases while Delhi had only 573 coronavirus patients under treatment in hospitals or under home isolation, which is 178% less.
On April 10, the worst day for Mumbai when the active cases touched a peak of over 91,000 was only slightly behind the worst for Delhi on April 25 when the active cases reached nearly 95,000.
But in Mumbai, the daily reported cases have stayed in the range of 500-100 since mid-June while Delhi has been registering less than 100 cases since July 4.
The answer for why Delhi is better placed in terms of daily reported cases perhaps lies in the seroprevalence figures of the ICMR, which recently conducted the fourth round of the national serosurvey.
But, it has not published the district wise data, including Delhi and Mumbai, which will give more insights into the pathogen’s penetration in these two cities.
Some experts believe that compared to Mumbai, seroprevalence, due to infection and vaccination, may be higher in Delhi. “I think at least 85% people in Delhi would have antibodies,” said health systems specialist Chandrakant Lahariya.
He feels a far “truthful and honest” detection of cases in Mumbai, its heterogeneity of population, which limits intermingling of people as compared to Delhi, and spread-out infection and slower vaccination could be the factors why the city is still reporting higher cases.
Numbers support what he says. For example, while 69,01,149 Covid-19 vaccine doses have been administered in Mumbai so far, it is 96,03,697 in Delhi. Oommen John, public health researcher associated with the George Institute of Global Health in the capital, too suggests that seroprevalence and extent of vaccination coverage.