Bengaluru: Some Luminaris has predicted a third covid wave in India will begin at the end of August and peak in October.
Naturally, everyone is quite worried.
The first wave (March to September 2020) peaked six months after the initial increase.
The second wave (March to 2021) peaked in six weeks – four times faster.
On average seven days run new cases every day at the top of the second wave (across four lakh) four times higher than in the first wave.
In the third wave, it will rise even faster with a higher daily number? Children, who avoid the first wave, pain in the second wave; Will this trend continue in the third wave? Waves are aware of clinical cases.
Draw as a graph, a bell-shaped curve and approximately symmetrical.
Waves arise from interactions between vulnerable population proportions and virus’ transmission efficiency.
The first is determined by ‘flock of immunity’ – proportion to the population immunity due to infection or vaccination.
The efficiency of transmission is a basic viral property, represented by ‘basic reproduction number’ r0.
Cause the plague, R0 must be more than one (R0> 1).
A wave recedes naturally after the level of the flock immune threshold is achieved, which is blown by R0.
Sequential waves are driven by consecutive variants – each with a higher R0 than its predecessor.
Our first wave variant (Wuhan D614G) has R0 = 1.5-2.5; R0 of the second wave (because the Delta variant) is four times higher: = 6-9.
Using the epidemiological formula based on R0 (the threshold of a flock of flock = 1-1 / r0) we calculate how much is infected by two waves; The first wave was infected around 476 million and the second wave of around 767 million.
Daily infections of around 40,000 more than seven weeks after the second wave adds a plateau, add up to two million.
Vaccination with the second dose has reached 10%, or 140 million.
Assuming a 30% previously uninfected person, 42 million more immune.
The remaining non-immune collection is around 113 million (8% of 1,400 million).
The fourth antibody survey (June-July 2021), by the Indian Medical Research Council, told us that the 67% of the people surveyed were positive antibodies without urban-rural differences.
Among children (10-17 years) 50% positive.
Antibody survey below the estimated immunity of true herds.
Two surveys show that only 64% and 80% (average 72%) of them with previous lab infections were positive antibodies.
With this correction, we obtained the immunity of herd at this time as 93%, leaving 7% non-immune – close to 8% originating before.
A small portion of the nonimmune population, plus our daily birth cohort is 60,000, sufficient enough to maintain a virus in a permanent endemic state, but it is not enough to allow waves, except the new variant with R0 is significantly higher than the Delta variant appears.
Virus has taught us not to underestimate its potential to mutate into a more contagious variant.
Screening for these variants among new infections must be a top priority for India.
T Jacob Johnms Seshadrid T Jacob John is a retired Professor of Clinical Virology, Christian Medical College, Vellore & Former President, Indian Pediatric Academy.
Dr.
MS Seshadri is a retired Professor of Medical (Endocrinology), Christian Medical College, and currently the Medical Director, Thirumalai Mission Hospital, Ranipet.