Covid-19: What you need to know today
This is the tale of three cities, Delhi, Mumbai, and Chennai, which were the first major hot spots of the coronavirus disease in India, and were responsible for most of the cases in the country in the early days of the pandemic’s run. Even in early July, these three cities were accounting for at least one in every four diagnosed cases of Covid-19, and by then, they were already starting to come off their peaks — as indicated by a declining positivity rate with increased testing. The positivity rate is simply the proportion of tests returning a positive result.
Yet, their trajectories present some interesting insights.
First, Mumbai. Over the past two-and-half months, Mumbai has upped its testing game. From around 3,000-4,000 tests a day in early June, it scaled up numbers to around 10,000 tests in late July, and even now, with the crisis seeming to have passed (the new hot spots in Maharashtra are the larger Mumbai Metropolitan Region, and Pune), is doing around 7,000-8,000 tests a day on average.
The worrying thing for Mumbai is that its positivity rate has fluctuated wildly — from 46% on June 1 when it was doing very few tests (just a bit over 3,000), to 6.8% on July 28 when it conducted around 10,200 tests, to 10% on August 11 when it did around 9,200, to 16.3% on August 12 when it performed around 7,000 tests. This volatility shows that the city’s administrators have been inconsistent when it comes to testing intensity. It also means that the testing in Mumbai is perhaps inadequate. They should be conducting more tests every day, perhaps at least 10,000 — every time they have exceeded this benchmark, the positivity rate has fallen to 10% or even lower.
Second, Chennai. HT’s dashboard has Chennai’s testing data only from July 3. The city has been more consistent when it comes to testing than Mumbai. The number of tests it has conducted in this period has never gone below 8,000, and the modal value is closer to 10,000. Its positivity rate shows an interesting trend. The consistency and adequacy of testing in Chennai meant that the city’s positivity rate touched around 10% in midJuly, and has largely stayed at the same level. For the past week, it has ranged between 7% and 9%. Interestingly, this has happened without any appreciable decline in the number of daily cases (once the positivity rate reached the 10% mark). Clearly, Chennai is going through a long plateau.
Third, Delhi. The Capital’s journey has perhaps been the most interesting. It definitely wasn’t testing adequately in June, and its positivity rate in the second week of June actually hovered around the mid-30s — which meant one in every three people being tested was found to be infected. The city ramped up testing rapidly, though, and by late June, the positivity rate fell to below 20%. By mid-July, with testing numbers continuing to remain high, the positivity rate came down to 6% and it has largely stayed at that level since. Like in Chennai, the number of daily new cases has remained rangebound (with a mode of around 1,000) since the positivity rate reached the 6% level. Delhi, too, it is evident, is seeing a long plateau.
Both Chennai and Delhi have to guard against the plateau becoming an upward slope. And Mumbai has to test adequately and consistently to get to the plateau, although it is almost there. Data on available hospital capacity in all three cities seems to suggest that the worst is behind them (there are beds available, even in critical care units).
All three cities do a mix of molecular (RT-PCR and NAAT) and antigen tests. The mix is skewed in favour of molecular tests in Chennai and Mumbai and antigen tests in Delhi. Given that all three cities are seeing (or beginning to see) a plateauing of cases, they should try and use molecular tests to the extent possible, especially if they have the capacity.