Just when it looked like Delhi would slip into complacency in its fight against the coronavirus disease, the state government has stepped up its game — or at the least, announced its intent to (see page 1). For at least a week now, HT has been pointing to the number of daily cases and the positivity rate inching up — not alarmingly, but definitely worryingly.

According to the HT database, the seven-day average of daily cases in the Capital peaked at 3,446 on June 26, before falling to below 1,000 in late July, and then again in early August (although this can, in part, be attributed to the weekend and public-holiday factor, where testing, and consequently the number of cases recorded, drop off). It has since climbed, and was at 1,333 on August 25.

It isn’t just cases, the positivity rate has also increased. The seven-day average positivity rate, which saw its peak of 31.4% on June 14 and 15 fell to 5.7% in late July, stayed at that level for some time, but has since climbed back. It was at 7.5% on August 25. In isolation, that is an impressive number for a state that is testing adequately, but relatively, it still marks an increase.

Also read: India’s Covid-19 tally over 3.2 million, recovery rate rises to 76.29%

Delhi is also definitely doing fewer tests than it used to: the seven-day average of tests peaked at 21,660 on July 9 but has since fallen. It was 17,924 on August 25. The Capital is not utilising the entire capacity of RT-PCR tests available, relying instead on antigen tests. Sure, the latter helped it scale up testing in late June when cases were peaking, some containment zones were rife with cases, and hospitals were running short of beds. But even after that crisis passed, Delhi continued to depend overwhelmingly on antigen tests. In the week ended August 25, for instance, only 31% of the tests conducted were RT-PCR ones.

The Reverse Transcription Polymerase Chain Reaction (RT-PCR) test is a molecular test that is globally recognised as the best diagnostic for Covid-19. The only problem with it is the time involved — which, including logistical delays and those caused by backlogs, is around three to four days (although is possible to provide results in 24 hours). Antigen tests, in contrast, provide results within the hour — this means a person can walk into a testing centre, be tested, and wait for the result — but are not very reliable. They throw up a high proportion of false negatives, identifying infected people as uninfected. As this column has explained ad nauseam, it makes sense to use them when time is a constraint. And by mid-July, that certainly wasn’t the case in Delhi.

Delhi’s chief minister Arvind Kejriwal has now promised to double testing — which is good — although it isn’t immediately clear whether the government will at least use up the entire capacity of RT-PCR tests available to it. The government has also said it will strictly enforce rules on the wearing of masks in public places — adherence is lax in markets and parks — and social distancing.

Also read | Covid-19: Tracing India’s journey to two million cases

The trajectory of coronavirus disease in cities, provinces, and countries around the world suggests that most regions see a long plateau once cases have fallen to a retain level. The trajectory of the disease in Delhi shows a narrow peak (itself a rarity), and it is evident that the Capital is now seeing the plateau. The challenge before the administration is to keep the plateau at a manageable level in terms of number of cases — there is no shortage of hospital beds (in fact, there is a surplus capacity), and the government must ensure it stays that way.