As Covid-19 cases rise, testing in 4 most affected cities slowing

Better testing is key to identifying new areas of the surge before they turn into hotspots.

Scientists and doctors know more about Omicron a month after it was declared a coronavirus variant of concern and rapidly spreads across the world and Indian cities.

Test positivity rate--the percentage of all coronavirus tests that turn out to be positive --is rising in Mumbai, Pune, Delhi and Bengaluru, four of the most-affected cities. Here, weekly averages of confirmed cases and laboratory 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 (averaged) has risen from a steady cling to 0.5 per cent in the first two weeks of December, to 1.58 per cent in the seven days ending 27 December. (The daily test positivity rate has crossed 2 per cent). 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 to 1.6 per cent.

The positivity rate in Delhi was below 0.1 per cent until December 1, but has since risen to 0.4 per cent. The positivity rate has more than doubled in the last week. The number of infections during this period has nearly doubled. 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.

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

Early December, the four cities did ramp up testing. 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. The testing rate has not increased as such. Mumbai, which went from 2,300 tests per million per day to close to 3,000, has fallen back to 2,800 tests per million per day in recent days. Weekly average of tests is used here.

Pune's testing is weaker than the three metros though the Maharashtra city appears to have scaled up in recent weeks. Testing rates in the country as a whole are in the range of 800-850 tests per million per day.

Better testing holds key to identifying new areas of the surge before they turn into hotspots.