Numbers Matter | What early signs of Covid peak in Mumbai, Delhi mean for India

Jan 12, 2022 01:46 PM IST

Milder infections, coupled with fewer hospitalisations also means that a minuscule case of infections will end up being severe

Around the middle of December, a slow but steady increase in cases of Covid-19 was first observed in two cities – Mumbai and Delhi. By the end of the year, as more and more cases of the highly transmissible Omicron variant were being reported (a large proportion of them in these two cities), it became apparent that what these regions were facing was indeed the third wave of infections in India.

But the good news is that for now, the waves in Mumbai and Delhi appear to be following trends seen in Omicron waves the world over(PTI) PREMIUM
But the good news is that for now, the waves in Mumbai and Delhi appear to be following trends seen in Omicron waves the world over(PTI)

By early January, this wave has transcended to nearly all parts of the country, and the national wave started rising at a rate that had never been seen before. On December 28, for instance, there were 9,155 new cases of Covid-19 reported across India, according to HT’s Covid-19 dashboard. Just eight days later, on January 5, there were 89,972 daily infections in the country. To give context to how fast this rise is, the jump from 9,000 cases to around 90,000 cases took 46 days during the country’s brutal second wave (there were 9,150 new cases on February 15, 2020, and 89,030 on April 4).

And Mumbai and Delhi, being the earliest outbreak centres in the country, also saw some of the fastest rise in infections. On December 27 (a Monday), Mumbai and Delhi reported 788 and 331 new infections respectively. Exactly a week later, this number had jumped nearly 10-fold in both cities – there were 7,928 new cases in Mumbai on January 3, and 4,099 daily infections in Delhi.

But these two megacities have also been the first regions in the country to present encouraging signs.

In Mumbai, for the first time since the start of the third wave, the positivity rate has started dropping. Positivity rate (the proportion of daily tests returning positive for Covid-19) is one of the first statistical measures that changes to indicate a reversal in trend. This number has now fallen for five days in a row – the figure was 29.9% last Thursday, 29% on Friday, 28.6% on Saturday, 28.5% on Sunday, 23% on Monday, and touched 18.8% on Tuesday.

This trend positivity rate trend, as expected, was closely followed by a drop in daily infections in the country’s financial capital, which have now fallen for four consecutive days – there were 20,971 cases on Friday, 20,318 on Saturday, 19,474 on Sunday, 13,648 on Monday (numbers on Mondays generally fall due to reduced testing seen on Sundays), and finally 11,647 on Tuesday.

While daily cases in the Capital more than doubled in four days from 10,665 on Wednesday to 22,751 on Sunday, cases have stayed below Sunday’s level over the two following days – there were 19,166 new cases on Monday (when fewer tests were conducted), and 21,259 on Tuesday. The rapid rise in positivity rate in Delhi has also slowed. While the daily positivity rate jumped more than 11 percentage points between Wednesday (11.9%) and Sunday (23.5%), it has only increased two percentage points in the two days since (it was 25.6% on Tuesday).

If this trend continues, Delhi may soon be headed to a peak in a few days, something that Delhi health officials have suspected may happen based on an analysis by a team of medical experts along with an assessment of Sutra – a mathematical model developed by scientists at IIT-Kanpur and IIT-Hyderabad – that says that Delhi could see a peak in Covid-19 infections around January 15.

But there are caveats.

A crucial aspect that experts feel is being overlooked is the role of rapid home-testing kits in hiding the true on-the-ground numbers from these cities. Doctors feel that a lot of people have resorted to using home test kits as they have been reporting mild, or asymptomatic infections (which is far more common in the Omicron variant than it was during Delta), and do not necessarily follow up with an RT-PCR test if they are positive, thereby staying off the radar. There is, however, no way to map these cases since most mild patients are recovering in home isolation.

Infectious disease expert Dr Om Srivastava, who is also a member of Maharashtra’s Covid-19 task force, said that the wide use of self-testing kits is a matter of convenience but when looked at from a public health perspective, it could present a skewed picture of the spread of infection. “The authorities should consider devising a mechanism through which reports of all self-tests are recorded,” he said.

Furthermore, the reversal in trajectory (if it continues, in the first place) in these two cities hardly means that the battle against the country’s Omicron variant is over.

Outbreak numbers are still bad in the other early urban outbreak centres like Chennai and Kolkata. In Chennai, both cases and positivity rates are rising alarmingly fast – in the past week, new cases have gone from under 1000 to more than 6000, and the positivity rate has jumped from the 4-6% range to close to 18%.

The wave is expected to see an even wider and more sustained growth in larger states with large rural populations in the coming weeks, and as per most models, the national wave won’t peak until early February.

So, what’s the course ahead? Simply put, the basics remain the same – social distancing and masking become even more relevant in a far more transmissible variant like Omicron. Secondly, while hospitalisations (in both proportion and absolute numbers) remain far below numbers seen during the Delta waves for now, if daily cases continue a nation-wide rise, then even a minuscule proportion of active landing up in hospitals may raise the danger of stretching a region’s health infrastructure thin.

But the good news is that for now, the waves in Mumbai and Delhi appear to be following trends seen in Omicron waves the world over – a very rapid rise in infections that peaks just as fast (and importantly recedes just as fast as well), coupled with a relatively higher share of mild cases, which causes a far smaller share hospitalisation. Milder infections, coupled with fewer hospitalisations also means that a minuscule case of infections will end up being severe, and an even smaller proportion of them are likely to die.

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    Jamie Mullick works as a chief content producer at Hindustan Times. He uses data and graphics to tell his stories.

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