1. With reference to my earlier published research paper (Cited as Reference No. (1) below).In this study, published in the end of June, it was estimated that by around the beginning of August 2020, “flattening of the COVID epidemic curve” may start. It seems to have happened, in the third week of August, though not in the beginning.
2.The above finding does indicate a need to ponder on the relevance of so widely quoted concept of “herd immunity”. Recently, a report (end of July / beginning of August) from AIIMS Delhi indicates that, while establishing the baseline for the vaccine trial, the population which had to be excluded from entry into the forthcoming trial due to existing detectable antibodies was approximately 20%. If we compare it with the general baseline of the ICMR sero-survey of end April, which gave an overall prevalence of approximately 1%, we would realize that in just 3 months, the sero-positivity and, as a surrogate indicator, the proportion of infected population has increased 20 fold in just 3 months.
3. Against the foregoing statement, I have some dissension regarding the often quoted “magic figure” of 60 to 70% “Herd Immunity” required to protect the population. Firstly, to the best of my knowledge, there is NO study which has scientifically proved this figure; it is more of a religious commandment rather than a reality. In fact, for certain diseases, the herd immunity required may be as high as 85% to 90% for being protective. However, the point that I wish to make is different: herd immunity is a “continuously distributed” and NOT a “Categorical” phenomena, so that the moment it reaches 60%, it will start protecting and will just not be protective when it is 59%. Even at herd immunity levels of 20%, some population protection may start, and such protection will gradually increase as the level of herd immunity keeps rising; once it reaches 60 to 70%, considerable protection may be imparted to the population. The apparent initiation of flattening of curve being noticed in Delhi, at the level of 20% sero-prevalence may be an early testimony of what I am expressing here.
4. I submit the viewpoint that, as of date, in the face of a massively mounting epidemic, we need to focus turn our “disadvantage” into “advantage” by focusing on certain very helpful aspects in the epidemiology and transmission dynamics of this disease, which have become quite apparent by now:
(a) That almost 90% of the transmission occurs due to “droplet infection”, through droplets generated by an infected person in the act of sneezing, coughing, singing or talking with force, within a distance of 6 feet of the potential recipient; only 10% of the transmission would occur through surface transmission due to contamination of inanimate articles (as furniture) or through fomites and, that too, in very specific settings of homes, hospitals, public toilets, and dense human congregations as social or religious events. Transmission by “air-borne” route in which the infective particles can be carried over long distances seems to be a rarity.
(b) That 85% of the infected persons would be asymptomatic and, in all probabilities, will NOT transmit the disease or will have a very minor contribution in transmitting this disease at the population level.
(c) That despite the uncertain and very wide incubation period of 1 to 14 days, almost 80% or more of the persons who will develop symptoms (and hopefully, will be the ones who will transmit the disease) will have the onset in 5 to 7 days of acquiring infection and that, with 90% probability, they will transmit the disease in a narrow range of 3 to 5 days, i.e., from a day or two before the onset of symptoms (the “pre-symptomatics”) to 2 or 3 days after the onset of symptoms (the “symptomatics”). So, detecting the “Cases”, isolating them for maximum of 3 to 5 days (or, let us say maximum of 7 days in case we want to over-ensure) at home (if mild) or at hospital (if severe / critical) and effectively treating the severe / critical cases will take care of a big chunk of our problem of transmission as well as the problem of severe morbidity / mortality.
(d) That a large majority of transmission occurs in “closed communities” or “human conglomerations” (notably within the family, where the transmission may be almost 100%). By the time we are able to track and test the close family contacts or contacts of the said “conglomeration”, whatever transmission had to happen would have already occurred within these 2 to 3 days following onset of symptoms.
(e) Rather than adopting the “test-track-test-quarantine” strategy for contacts at this stage, which is going to be an insurmountable task and may strain out the already stretched healthcare resources, the better option would be to identify the “high transmission areas”, undertake a house to house survey in these areas, identify any person with ILI, isolate (at home or hospital) and treat.
(f) That till the time we are able to deliver an efficacious vaccine to the large masses, we need to appreciate the efficacy of masks, which if used by even 70% of the population may have the same population protective effect as the vaccine itself. So let us mount public health actions to enforce the population-wide use of masks. It is easily said than done, though. In my own medical college hospital, there is not a single day when I don’t have to shout at the top of my voice on my own health-care team members, for being complacent in the use of masks.
(f) The “infection to mortality ratio” is very low, less than 2% at present and in the long run may settle down at less than 1%. So, rather than getting into a scare, let us build up a policy as follows for the present:
(i) Universalize the use of face masks by public education and, if required, by coercive methods
(ii) Energetically identify those having symptoms of ILI / SARI, test them and isolate them at home (mild ones) or at healthcare establishment (severe or critical) and treat
(iii) For the present, do away with the strategy of tracking, testing and quarantining the contacts, which seems to be like “chasing the shadows”
(iv) Concentrate more on undertaking “Economic” repair” rather than concentrating on “quarantining the disease”, which is going to be an uphill task at present, in the face of an overwhelming epidemic.
References.
- Bhalwar R. Lockdown for Covid‑19 in India: An alternative viewpoint and revised epidemiological estimates. Pravara Med Rev 2020; 12: 2: 4‑10.
- Banerjee, A. Chasing the Virus: Not Only Difficult but Impossible. Are we going to Hit a Dead End? (Editorial). Medical Journal of Dr. D.Y. PatilVidyapeeth, 2020. Published by Wolters Kluwer – Medknow (Downloaded free from http://www.mjdrdypv.org on Monday, August 10, 2020, IP: 110.227.213.25).
JAI HIND
Air Vice Marshal (Retd) Dr. Rajvir Bhalwar
M.B.B.S (Lko),M.D (Public Hlth / Prev. Med) (Pune), Ph.D (Public Hlth / Prev.Med) (Pune), F.A.M.S., FIPHA
Post-Doctoral Training (Clinical Epidemiology)(INCLEN)
P.G Dip.Hosp.Mgmt(Del), P.G. Dip (Med Laws) (NLSUI B’lore)
Dean,
Medical College,Pravara Institute of Medical Sciences (Deemed University)
Loni – Bk, Near Shirdi, Tal. Rahata, Dist. Ahmednagar, Maharashtra, PIN – 413736
