More tests (9.66 million as of Tuesday night) than any other state except Uttar Pradesh and Bihar. The use of reverse transcription polymerase chain reaction (RT-PCR) tests alone, unlike UP and Bihar, which have largely used rapid antigen tests. Around 127,000 tests per million population. These are some of the Covid-19 metrics from Tamil Nadu, and they are impressive.
The southern state has seen 714,235 Covid-19 infections (as of Tuesday), the fourth highest in the country after Maharashtra, Andhra Pradesh and Karnataka; and recorded 10,983 deaths, the third highest in the country after Maharashtra and Karnataka. Its fatality rate of 1.53% is slightly higher than the country’s 1.5%, and its cumulative positivity rate of 7.4% is about the same as the country’s 7.57%. These are some of the Covid-19 metrics from Tamil Nadu, and they aren’t that impressive.
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However, as the first wave of the coronavirus pandemic ends in India, I would like to believe that Tamil Nadu is the state that has best handled the health crisis. This is why.
The first reason is the test.
For a state with a population of about 76 million, testing 127,000 people per million is an achievement. India’s total number is 79,141 tests per million. And Tamil Nadu continues to aggressively test (see box). Significantly, the status is based exclusively on gold standard molecular RT-PCR tests. I have written extensively about the dangers of indiscriminate use of rapid antigen tests; Their false negative rate is around 50%, which means they miss infections in about half of people who carry the virus. India’s number of 79,141 per million is based on rapid antigen tests. UP and Bihar trust them; even Delhi uses many more of them than it should. Tamil Nadu’s reliance on RT-PCR testing means that its positivity rate data is much more credible.
The second is the trajectory of positivity rates over time in the state.
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The positivity rate is simply the number of people who tested positive expressed as a percentage of the number of tests performed. Tamil Nadu’s positivity rates started out high (when very few tests were being done), decreased as the number of tests increased, then increased again as the infection spiked, then decreased and stabilized with consistently high tests, and it finally began to decline. The seven-day average has been below 5% for two weeks, and the daily number at or below 5% for the past 10 days (see chart). The World Health Organization said in May that a rate below 5% for two weeks meant the pandemic was under control. Certainly, this benchmark must be achieved even if the evidence remains consistently high and the correct type of evidence is used (Tamil Nadu satisfies both conditions).
Both factors are reflected in the state’s current Covid-19 metrics. On October 27, Tamil Nadu saw just 2,522 cases, 5.85% of all cases recorded that day. Even the seven-day average of daily cases has fallen: it was 2,866 on October 27. After a long plateau during August and September (and a peak in July), the trajectory of daily cases has fallen to October.
The same is reflected in the number of deaths. On October 27, Tamil Nadu recorded 27 deaths (seven-day average: 35), well below the peak seen in August. Like the daily case numbers, the death toll leveled off for much of September before starting to fall in October.
Other states would do well to read the charts that accompany this column carefully; this is what a successful Covid-19 management strategy looks like (without using the wrong type of evidence or controlling for case numbers through inadequate testing).
Does this mean that the number of cases will not increase again in Tamil Nadu?
Definitely not. They could. In May, overcrowding at a vegetable market in Chennai triggered a rebound. Earlier this month, terrifying videos of crowds were broadcast at a Chennai sari shop (already sealed by the local administration). Any such silly behavior could result in an increase in cases.
And does this mean that Tamil Nadu will remain isolated from the inevitable second wave?
That is highly unlikely, but state administrators have a proven strategy to follow.
That’s more than can be said for many other states or territories in the Union.
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