Why Kerala is unable to bring its epidemic curve down?

Kerala’s epidemic curve, after scaling the peak in mid-May when the test positivity rate was around 30% and approximately 44,000 cases were being reported daily, has since the past four weeks settled at a level wherein an average of 12,000 new cases are reported daily and the TPR is steady at 10-11%.

Why does Kerala continue to report a huge number of cases daily when the case graph has plunged in other States? Unlike in other States, why is the epidemic curve in the State staying on a long plateau?

It is a combination of factors peculiar to Kerala as well as the consistent manner in which the State has been responding to the pandemic that has the State still riding a long plateau out, public health experts believe

“All nations which successfully managed COVID have a similar epidemic curve as Kerala, wherein the curve rises gradually, spreads out and after the peak, declines gradually. This indicates controlled transmission and sustained containment measures, wherein the virus is never allowed to run riot and overwhelm the health system capacity, “says T. S. Anish, a public health expert and a member of the State’s expert committee on COVID-19.

“Wherever the epidemic curve has risen and fallen sharply, the duration of the epidemic might be less but it would have resulted in significant mortality. Such places are also at risk of a new wave . Kerala’s attempt was to prevent a sharp rise in the epidemic curve so that the impact on the community was reduced. In fact the State’s strategies are an investment to prevent a third wave,” says Dr. Anish

Post first wave

Kerala’s epidemic curve is not behaving any differently now than it did after the first wave peaked in October end. The curve continued to remain on a plateau till February when the large scale gatherings and mixing of people during the general elections and the arrival of Delta variant led to the second wave.

“There are many situations when an epidemic curve does not return to the baseline and the reasons range from the infectiousness of the virus to people’s behaviour during the pandemic. Kerala was already having 2,500 plus cases daily when the second wave began rising,” points out Rakhal Gaitonde, public health expert and Professor, SCTIMST.

“After the first wave, when the curve plateaued, we had reached a certain level of efficiency in controlling transmission, with our compliance to masking and other COVID protocols. But then the arrival of the Delta variant changed the scenario completely. Because this variant is highly transmissible, the same level of efficiency in transmission control will not be enough, which is why the curve has plateaued at a much higher level of cases,” he adds.

Dr. Gaitonde points out that when one compares Kerala with other States and berates the State for its inability to bring down the case graph, one should also consider the level of testing that is done in other States. Testing has plunged in other States while Kerala is doing COVID tests at the same level as it was doing at the height of the second wave, he says.

Public health experts also point out that Kerala is one homogenous population, which is highly mobile and with no urban-rural divide. Large-scale mixing of population is sustaining disease transmission here. It is different in other States, where, cases began to be reported less when the disease moved from the urban to rural areas.

Case reporting fidelity

“The case reporting fidelity is affected as soon as the disease moves from urban to rural areas, where people do not test for COVID and unrecognised deaths may be happening in homes. This gives the impression that in these States, the pandemic has subsided,” Dr. Anish points out.

Also, according to ICMR’s sero surveillance study in January, 89% of the population in the State was still naive. Even after the second wave has peaked, given that Kerala is missing only one in three infections in the community, less than one crore of the State’s population would have been infected so far .

Delta is one of the most evolved virus variants and as long as there is a susceptible population, transmission is likely to be sustained. In a nutshell, Kerala is paying the price for its better containment efforts

It is thus a combination of factors – the urban-rural continuum, social behaviour of the people, the highly transmissible virus variant itself, the efficiency of non-pharmacological interventions in controlling transmission and finally, the pace of vaccination drive which is determining the behaviour of the pandemic curve in the State.

Public health experts also point out that the Centre’s obsession with test positivity rate (TPR or the proportion of people who test positive amongst those who get tested) puts undue pressure on States.

TPR is not as reliable or as robust an indicator of disease transmission as senior administrators would like to believe because its reliability is highly dependent on who is being tested – and this is something easily manipulated at the lower rungs

“If one were to restrict COVID testing to those who are symptomatic or who are primary contacts of a positive case or those at high risk of infection, the TPR would naturally be very high. For a local body administrator, an honest assessment of TPR in his locality would be impossible because a high TPR is equated to inefficient COVID containment,” a senior public health expert points out.

He suggests that the TPR data should be disaggregated – ie, the TPR amongst the symptomatic, primary contacts and the general community should be tabulated separately for the data to be accurate and useful.