India’s Covid-19 positivity rate – the proportion of people testing positive to those tested – is increasing. The weekly average is around 11.7% now. The number has steadily increased. It was around 8.1% a month ago. In early May, it was as low as 3%. Contrary to what this trend may immediately suggest, and concerns being expressed by some experts, a rising positivity rate in India, under the current context, is actually good news.
India has thus far carried out around 11,310 tests per million of the population. This number too has been increasing steadily; over the past week for instance, India carried out 333,697 tests a day on average. It should be doing a million a day, but the current number is still higher than the 143,565 tests a day it was conducting in mid-June. This increase is responsible for the country’s rising positivity rate.
As regular readers of this column know, the positivity rate increases with testing till a point, then plateaus, and then eventually starts declining as a country, state, or city starts testing adequately. At the current level of testing, India has tested around 1.1% of its population. That’s way too low. There are countries that have done 10-12%, but given India’s size and population, the country should be aiming for testing at least 5% of the population.
It is important to understand how to read the positivity rate. A low rate is desirable, but only when accompanied by adequate testing. There are states that show a low positivity, but this isn’t because they have few cases, but because they aren’t testing enough. Uttar Pradesh, Odisha and Bihar, for instance, have low positivity rates, but are clearly not testing enough, and so while absolute numbers may suggest that they are better off than other states in managing Covid-19, they actually aren’t. In fact, the reverse is probably true.
Telangana and Gujarat have higher positivity rates, but they too are clearly not testing adequately (which is actually even more worrying).
In contrast, Delhi has a high positivity rate (cumulatively), but the number is way off its peak (when the trend in daily positivity rates is seen; for instance, it was only 5.7% on Thursday), an indication that things have gotten better in the Capital (which is also reflected in the falling number of daily cases). And it is testing a lot (around 4.4% of its population has been tested at last count). Tamil Nadu presents another narrative. It is testing adequately (it has tested 2.8% of its population at last count, a significant number for a state with a population of around 80 million), and is just about maintaining its positivity rate (which means the daily cases are still high) – an indication that the state is on the long plateau that comes before the dip. The state’s positivity rate is way off the peaks it once scaled, perhaps an indication of just how badly inadequate testing can skew this metric in either direction.
It’s easy to understand – given this behaviour – why most experts maintain that a positivity rate between 7% and 12% (some are a lot more specific and put the number at 10%) is a reflection of adequate testing. Given the Tamil Nadu example, this proportion seems to correspond with the ideal positivity rate in the plateau-phase of the curve.
So, how high can India’s positivity rate go? That’s a tough question to answer, but if the country were to sharply increase testing – say, reach the million-test-a-day mark that I’ve been suggesting – it will reach this peak very soon.
Still better, it won’t stay there very long if it keeps up the intensity of testing.