• Rajvir Bhalwar- Public Health, Epidemiology & Research Methodology

## WHAT IS THE “EPIDEMIOLOGICALLY CORRECT” MORTALITY MEASURE : INFECTION FATALITY RATE OR CASE FATALITY RATE

1.      In the current COVID scenario, the fatality rate is being calculated as {(Cumulative Number of Deaths as on that date)÷  (Total number of cases detected as on that date) * 100)}. For example, for and up till 22 / 23 July midnight, it is being calculated as {(29890)÷ 1239864) * 100) = 2.41%.

2.      From the epidemiological point of view, there is an intrinsic flaw in the way the so called “Case Fatality Rate” is being calculated and reported, as described in para 1 above. The reason is that while the numerator (total number of deaths) is OK, but the denominator (Total cumulative total of all those found to be infected) is not correct, because a number of persons in such denominator have a definite probability of moving on into the numerator in the next few days (to simplify, a number of persons out of the “total positive cases” as on today, are likely to die on subsequent days).

3.      The correct method of calculating the Case fatality Rate (CFR) in this scenario should be :              {( Cumulative Number of Deaths as on that date)÷  (Total number of persons who have reached the “end point” as on that date, i.e., have either been discharged as recovered plus those who have died) * 100)} This is the correct method and if we work out the data, the CFR on midnight of 22 / 23 July will be {(29890) ÷(784266 + 29890) * 100} = {(29890) ÷ (814156)} * 100 = 3.67%.

4.      The point that I wish to make is not simply pertaining to mathematical semantics. If we plot the data on CFR (as calculated in para 3 above), for the 2 month period of 23 May to 22 July, we would appreciate that there has been a very significant and consistent decline in the CFR every day from 6.70% on 23 May to 3.67% on 22 July. However, during the past 5 or 6 days, though there is a fall, this decline has become less marked as compared to what it was previously.

5.      We need to study this aspect. Is it that our healthcare efforts have become saturated, so that whatever decline in mortality we could have achieved by quick diagnosis and prompt, complete treatment, has been, by and large, achieved and now to achieve further sustained and significant decline in mortality, we need to re-look at our case management protocols? Or, is it that after the initial 15 to 20 cycles of transmission in the population during which the virus reduced in its virulence, now it is getting stabilized as far as its infectivity, pathogenicity and virulence is concerned.

## Tackling the COVID-19 Epidemic : The “Herd Immunity Factor”

Spread the love1. With reference to my earlier published research paper (Cited as Reference No.…

## WHAT IS THE LIKELY “BASIC REPRODUCTION NUMBER (R0)” OF SARS-COV-2 AT PRESENT?

Spread the lovePrologue: Ever since the present COVID pandemic unleashed its fury on mankind, an…