The third wave of coronavirus disease (Covid-19) infections in Delhi has started showing clear signs of receding with new cases dropping steadily over the past few weeks. The reduction in new infections has come hand-in-hand with a drop in the positivity rate and a significant improvement in testing, suggesting that the outbreak in Delhi may be relatively under control for the third time. Here are four factors that show Delhi is on the right track in its battle against the viral outbreak.
1. A distinct drop in the third wave
Delhi’s Covid-19 case trajectory has shown three distinct surges. The first started in mid-June, and peaked when the seven-day average of daily cases, also known as the case trajectory, touched around 3,400 in the last week of June. This receded by the end of July when the trajectory dropped to around 1,000 daily cases. The second wave started at the end of August, rising until mid-September, when average daily cases touched 4,174 for the week ending September 17. This again dropped to 2,574 in the week ending October 9, before the onset of the third wave.
The third wave raged through most of October and November, leading to the largest surge of cases the capital has seen. The seven-day average of new cases peaked on November 14, when it touched 7,341 – the highest recorded so far. Since then, however, cases have started receding almost steadily (albeit with a slight bump on November 19 and 20).
2. Testing better and testing more
While Delhi has been ramping up Covid-19 tests from as early as September, a key concern was that most were rapid antigen tests, which are cheap, and produce results within 15 minutes, but unreliable. The proportion of reverse transcription-polymerase chain reaction (RT-PCR) tests, considered by experts to be the “gold-standard”, dropped significantly. In the first 15 days of September, while overall testing rose, the share of RT-PCR tests nearly halved – from 32.3% in the week ending September 1 to 17% in the week ending September 16. This may have suppressed the real positivity rate because studies have shown that rapid antigen tests can miss as much as 50% of positive cases.
But in the past few weeks, this has not been the case. In the past week, 47.5% of all tests done in Delhi have been RT-PCR tests – the highest proportion ever recorded since the Delhi government started releasing a breakup of testing numbers in the last week of August. Meanwhile, the rate of testing (both RT-PCR and antigen) is at the highest ever. On average, the Delhi government has conducted 64,148 tests every day in the last week. In fact, 78,949 samples were tested on Tuesday, another single-day testing record.
3. Dropping positivity rate a good sign
The positivity rate for Covid-19, meanwhile, has again started dropping. In the last week, 7.3% samples tested have come back positive (this is the lowest in over a month, since 7.2% for the week ending October 26). The proportion was 11.2% the week before, and 13.3% the week before that. On Wednesday, it was 5% — the lowest single-day positivity rate in nearly two months (it was 5% on October 6).
The positivity rate is a crucial metric as experts say it shows how widespread the virus is in the community, and when coupled with increasing new infections, indicates that the virus is spreading rapidly. A rising positivity rate typically suggests that a region is testing inadequately. The average positivity rate should drop to 5% or below if the testing programme is adequate and is keeping the outbreak in control, according to the World Health Organization (WHO). That is why testing enough, and using the right kind of tests, is the key to Delhi being able to control the outbreak in the next few weeks.
4. Another relief: Covid deaths dip again
As Delhi grappled with the third wave of infections, another alarming trend emerged – daily deaths were rising at an alarming rate again.In the week ending November 24, 116 people died every day on average of Covid-19. This was the highest death rate since mid-June (to be sure, deaths in this latter period were artificially inflated as Delhi retrospectively added fatalities that had been wrongly not attributed to Covid-19, according to the Delhi government).
From the peak in the week to November 24, however, deaths have again started inching down, with 89 people a day on average, dying of Covid-19 in the past week.
Source: Delhi government Covid-19 bulletins, HT’s Covid-19 dashboard