Why Delhi may be on the right track in the Covid-19 fight
The third wave of coronavirus (Covid-19) infections in Delhi has started to show clear signs of receding with new cases steadily declining over the past few weeks. The reduction in new infections has gone 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 clear fall into the third wave
The trajectory of the Covid-19 case in Delhi has shown three distinct waves. 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 in late July when the trajectory narrowed to around 1,000 cases a day. The second wave began in late August, increasing through mid-September, when the average daily cases reached 4,174 for the week ending September 17. This fell back to 2,574 in the week ending October 9, before the start of the third wave.
The third wave lasted most of October and November, prompting the largest increase in cases the capital has seen. The seven-day average of new cases peaked on Nov. 14, when it hit 7,341, the highest on record so far. Since then, however, cases have started to recede almost steadily (albeit with a slight rebound on Nov. 19-20).
2. Try better and try more
While Delhi has been ramping up testing for Covid-19 since September, a key concern was that most were rapid antigen tests, which are cheap and produce results in 15 minutes, but not reliable. The proportion of reverse transcription polymerase chain reaction (RT-PCR) tests, considered by experts as the “gold standard”, was significantly reduced. In the first 15 days of September, while general testing increased, the proportion of RT-PCR tests nearly halved: from 32.3% in the week ending September 1 to 17% in the week which ended on September 16. This may have suppressed the true positivity rate because studies have shown that rapid antigen tests can miss up to 50% of positive cases.
But in recent weeks, this has not been the case. In the last week, 47.5% of all tests performed in Delhi have been RT-PCR tests, the highest proportion ever recorded since the Delhi government began publishing a breakdown of test numbers in the last week of August. Meanwhile, the testing rate (RT-PCR and antigen) is the highest ever. On average, the Delhi government has conducted 64,148 tests every day for the last week. In fact, 78,949 samples were analyzed Tuesday, another record for tests in a single day.
3. Lowering the positivity rate is a good sign
Meanwhile, the positivity rate for Covid-19 has started to drop again. In the last week, 7.3% of the samples tested tested positive (this is the lowest level in more than a month, from 7.2% in the week ending October 26). The proportion was 11.2% the week before and 13.3% the week before. 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 combined with the rise in new infections, indicates that the virus is spreading rapidly. An increasing positivity rate generally suggests that a region is not testing properly. The average positivity rate should drop to 5% or less if the testing program is adequate and keeps the outbreak under control, according to the World Health Organization (WHO). This is why testing enough and using the right kind of tests is the key for Delhi to be able to control the outbreak in the weeks to come.
4. Another relief: Covid deaths fall again
As Delhi grappled with the third wave of infections, another alarming trend emerged: Daily deaths were increasing at an alarming rate again. In the week ending November 24, 116 people died every day on average from Covid-19. This was the highest death rate since mid-June (undoubtedly, deaths in this latest period were artificially inflated as Delhi retrospectively added deaths that had not been wrongly attributed to Covid-19, according to the Delhi government).
However, from the peak of the week to November 24, deaths have started to slowly decline, with an average of 89 people per day dying from Covid-19 last week.
Source: Delhi Government Covid-19 Bulletins, HT Covid-19 Panel