Covid-19 pandemic: Top cities see surge in cases, drop in testing

It has been more than a month since Omicron was named a variant of concern. Since then, while genomic sequencing is helping identify the severity of its spread, the resurgence in Covid-19 cases across major Indian cities cannot go unnoticed.

Confirmed cases in Mumbai are rising with a speed never seen before. They nearly doubled in a day on December 29, from 1,377 to 2,510, and rose 10x from the normal level of close to 200 in just over a fortnight. Delhi’s number is also doubling per day, raising concerns about a potent third wave. 

Test positivity rate, or the percentage of number of tests turning out to be positive, is rising in cities, including Mumbai, Pune, Delhi, and Bengaluru. Here, weekly averages of confirmed cases and lab tests have been used to arrive at a weekly test positivity rate, which refers to the seven days prior to any particular date.

Mumbai, Delhi, and Pune have shown a dramatic rise in the positivity rate in the most recent weeks. The uptick in Bengaluru seems to be a bit gradual, for now. 

Mumbai's weekly test positivity rate (weekly averaged) has risen from a steady cling to 0.5 per cent in the first two weeks of December, to 2.69 per cent in the seven days ending 29 December. Pune, which showed a high test positivity rate even in the period of low Covid-19 spread, has seen positivity increase from levels of 1.3 per cent in the initial days of December, to 2.2 per cent on 29 December.

The positivity rate in the national capital was below 0.1 per cent until December 1, but has since risen to 0.63 per cent. Positivity rate in Delhi has more than tripled in a week. On the other hand, the rise in positivity rate in Bengaluru has been slower than Delhi. The positivity rate in the tech capital has risen from 0.4 per cent to 0.6 per cent in less than 10 days as of December 28.

This should naturally nudge the civic administrations to ramp up testing, targeted in localities or wards where the positivity rate is rising fast.

In the initial weeks of December 2021, the four cities did ramp up testing to some extent. This could have been in response to the spread of Omicron through international travel, and increased testing and airports coupled with contact tracing. But in the second fortnight of December, testing has dropped.

Except Pune, the three other cities show a clear drop in testing in the days close to Christmas and as 2021 draws to an end.

Delhi has been averaging 56,000 tests daily, at a rate of close to 3,000 tests per million per day. Mumbai, which went from 2,300 tests per million per day to close to 3,000, has fallen back to 2,900 tests per million per day in recent days. Weekly average of tests is used here.

Pune’s testing effort is weaker than the three metros. Though it seems to have ramped it up in recent weeks, the levels are lower than peers. Testing rates in the country as a whole are in the range of 800-850 tests per million per day.