Covid-19: What you need to know to today

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Tamil Nadu on Thursday crossed the million mark in terms of number of Covid-19 tests. It was the first state to do so. That translates to around 15,000 tests per million of population (or 1.5% of the population), lower than Delhi’s 23,000+ and even Andhra’s 15,000+, but still among the highest in the country. The number is also much lower than that in some of the countries ravaged by the coronavirus disease — the US, UK, Spain, Russia, Italy, that have all tested between 8% and 12% of their population -- but it is still higher than the national average in India of around 5,834 tests per million of population.

The state has rapidly increased testing. On June 11, it carried out only 16,829 tests. By June 25, this number increased to 32,543. And its daily positivity rate hasn’t changed much. This is a measure of the number of positive tests to the total tests, expressed as a percentage, and it has gone from 11.14% on June 11 to 10.78% on June 25. The lowest daily positivity rate for the state in this period was 7.21% on June 20, and the highest was registered on June 11.

There are minor daily variations, but across a fortnight, Tamil Nadu’s daily positivity rate has hovered between 7.2% and 11.14%, with a median (middle) value of around 10%. And this, even as the number of tests have doubled.

Tamil Nadu may well be the first state in India to be testing enough. Its positivity rate is following the trend (described previously in this column) — an increase, then a plateau, and then, finally, as a country, state or city begins testing adequately, a decline. Still better, the positivity range is exactly what the World Health Organization and experts at the Harvard Global Health Institute recognise as adequate.


The chart accompanying this column shows the number of daily tests and cases and the positivity rate for the state for the past fortnight. Tamil Nadu recorded almost 71,000 Covid-19 cases till June 25, around 3,500 on that date alone. Of this number, 911 have died, and almost 40,000 recovered — a case fatality rate of 1.26% and a 2.22% death rate when closed cases (deaths and recoveries) are taken into account.

The trend could change — as this writer has previously said, it makes sense to study one over a sustained period, say, eight weeks — but based on current evidence, Tamil Nadu seems to have got its hands (and more importantly, head) around the large-scale optimisation problem that is the management of Covid-19. The number of tests, cases, hospital beds, ventilators, health care professionals, people under home isolation, and volunteers, are all in the mix, and it is now clear that any district, city, state, or country that manages to crack this optimisation problem can get the better of the coronavirus disease.

But even this level of testing may not ultimately indicate the prevalence of the coronavirus disease in a population. On Thursday, the US CDC said that only a tenth of the cases in the US may have been identified and recorded. That would mean around 10% of the country’s population was infected and mostly recovered without realising it (or died, in a few instances, without their deaths being recorded as Covid-19 deaths). CDC, news reports suggest, may have based its assessment on an ongoing serological survey that tests for antibodies in the population. Smaller tests of this nature have been carried out in various parts of the US (and this column has mentioned them, including the one in NYC), but this is the first large-scale antibody test.

Interestingly, Delhi will become the first Indian state/city to embark on such a test on Monday, with 20,000 randomly chosen individuals from various parts of the Capital being tested for the disease.

It is about time that happened.

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