A health worker checks the vaccination certificates of passengers arriving at the Bandra Terminus, Mumbai, January 20, 2022. Photo: PTI
New Delhi: As an infectious disease starts to spread, you can plot the number of cases on every subsequent day on the y-axis and passing time on the x-axis – and you’ll get the outbreak curve.
The curve of any infectious disease outbreak typically has a consistent rising part, a peak and then the declining part. And after a point, the curve starts to become more and more flat.
The number of new COVID-19 cases every 24 hours in Delhi has hovered around 12,000-15,000 for the last week or so. Before that, the city used to report 20,000 new cases every day for about two weeks. So there is reason to believe that Delhi’s COVID-19 outbreak curve is currently on the decline.
Similarly, in Mumbai, the new daily cases have been in the 5,000-6,000 range since January 16 – versus around 20,000 new cases per day in the first 10 days of January.
Kolkata’s curve also looks similar: The daily new cases touched an apparent high of 8,712 on January 9, since January 17 have averaged 1,500-2,500 a day.
So – have the outbreaks of these three metropolitan cities peaked? That is, have they passed the worst of their respective third waves?
The Government of India hasn’t yet said so. Both the government and other experts have said that to qualify for peaking, the curve has to keep declining for 10 consecutive days.
It’s true that the number of cases in Delhi, Mumbai and Kolkata have been on the decline – but it hasn’t been consistent. In all three cities, the number of new cases lies within a fixed range, but within that range, there has been day-to-day fluctuation.
Therefore, we can’t say with certainty if the novel coronavirus outbreaks in these cities have peaked.
Second, understanding the concept of peaking is important to understand why you can’t take off your masks and socialise freely. The peak does not mean the virus has withered away. It simply means that the rate of the outbreak’s expansion will decline from that point. This implies in turn that hospitals and healthcare workers will stop being overwhelmed and restrictions, if any, on public and/or social activities can be eased. This is the policy perspective.
For individuals, the prescription to follow COVID-appropriate behaviour and to get fully vaccinated does not change.
Next, even when the number of new daily cases starts to come down, we will have to read it together with the number of tests being conducted. The more we test, the more cases we detect. But if the number of tests are coming down, then the number of cases coming down may not be an actual decline, but an artificial one.
For example, Delhi’s test numbers briefly declined last week before picking up again.
For another, on January 17, the Centre shot off a letter to all states and Union territories in this regard. The letter said, “It has been seen from the data available on the ICMR portal” that testing has declined and “to ensure the effective track of the pandemic is kept and citizen-centric action is initiated, it is incumbent upon all states/UTs to enhance testing” (sic).
Third – and just as important: The peak for a country as big and as diverse as India almost never translates to simultaneous peaks in the various states. So at the same time Maharashtra is getting over its peak, Bihar or Uttar Pradesh may be getting started on the upward part of their outbreak curves.
Indeed, Karnataka, Tamil Nadu and Uttar Pradesh are currently reporting more and more new cases every day. In the first two states, the test positivity rate (TPR) – the fraction of people testing positive for every 100 people tested – has risen by about 15 percentage points in the last 20 days. Any TPR over 5% is considered bad. The TPRs of Goa and Puducherry are currently 40% and 43%. In Uttar Pradesh, the number of cases has more than doubled in the last week.
So headlines that talk about peaks in certain geographies – especially in metropolitan centres – do not mean that the country as a whole has peaked. Each state, in fact rather each district, needs to keep an eye on its own outbreak curve and draft policy accordingly.
According to health ministry data, the number of districts reporting a TPR higher than 5% was 515 in the week ending January 19 – versus 335 as of January 12. So the country as a whole is nowhere near its peak.
So while the outbreak curves of Delhi, Mumbai and Kolkata appear to be declining, many other parts of the country are just getting started. And until the outbreak curve of the whole country has peaked, we need to ensure the early gains in these cities aren’t squandered. Mask up. Wash your hands. Get vaccinated.