Arguing that the commonly used method for calculating the death rate of Covid-19 is not truly representative of the actual situation, a group of researchers from Mumbai and Thiruvananthapuram has suggested that the actual mortality could be even two times higher.
The death rate, also referred to as case fatality ratio (CFR), is calculated by dividing the total number of deaths with the total number of infections, and expressed as a percentage. For example, India’s CFR on Monday, with 9,990 deaths and 3.43 lakh cases, can be calculated to be 2.91 per cent.
But the researchers from International Institute of Population Sciences (IIPS), Mumbai, a deemed university and autonomous organisation under the Ministry of Health and Family Welfare, and Thiruvananthapurm-based Centre for Development Studies (CDS), a research centre backed by Kerala government and Indian Council of Social Science Research, argue that this is erroneous.
In a study now available for review, the researchers point out that deaths today are of people who got infected a few days earlier. Also, even if infections suddenly stopped today, deaths would continue for the next few days, the victims being people who are already infected or are in hospitals. Therefore, they argue, the denominator to be used in calculating CFR should not be current caseload, but an earlier caseload.
The researchers say that an internationally accepted time lag to be used for this is 14 days.
According to them, the number of dead today need to be measured against the caseload of 14 days earlier to arrive at a more accurate picture of the mortality. If that yardstick is applied, the current CFR in India jumps to 5.03 per cent.
For the study, data until May 14 had been used, and in that case the CFR rose from 3.23 per cent to 8.01 per cent.
“Case fatality ratio is illusive in that the same with 14 days delay for India is at least two times higher,” Sanjay Mohanty, professor at the Department of Fertility Studies at IIPS Mumbai, said. He also pointed to a study in ‘The Lancet’ journal which had used the same method in March to calculate CFRs of different countries.
Another set of scientists and epidemiologists considers the current CFR to be erroneous for an entirely different reason. These scientists insist that the mortality of a disease must be assessed against the total number of people who have been infected, and not just those who have tested positive. But since a large number of infected people are believed to be asymptomatic, and not everyone is being tested, the total number of infections is not available, certainly not when the epidemic is still unfolding.
At the end of the epidemic, however, a reliable estimate can be arrived at, and this estimate would be much higher that the number of confirmed infections that is currently being used for calculating CFR. In such a scenario, the CFR is expected to be well below 1 per cent, they argue.
The researchers from IIPS and CDS also claim in their study that just a 0.5 per cent of community transmission of the disease could lead to so many deaths in the 47-65 year age group that it would have the effect of reducing India’s life expectancy by one year.