|LETTER TO THE EDITOR
|Year : 2021 | Volume
| Issue : 4 | Page : 473
Commentary on “the curious case of the dog that did not bark”
Institute of Neurological Sciences, Apollo Hospitals, Hyderabad, Telangana, India
|Date of Submission||09-May-2020|
|Date of Decision||20-Jun-2020|
|Date of Acceptance||03-Jul-2020|
|Date of Web Publication||17-Jun-2021|
Apollo Hospitals, Jubilee Hills, Hyderabad - 500 096, Telangana
Source of Support: None, Conflict of Interest: None
|How to cite this article:|
Kumar S. Commentary on “the curious case of the dog that did not bark”. Med J DY Patil Vidyapeeth 2021;14:473
I read with interest the editorial by Amitav Banerjee, where he has very nicely demonstrated the lower death rates in South Asian and African countries as compared to the USA and European countries. This is despite the fact that the developed nations have better health-care facilities-higher doctor: patient ratios, more number of intensive care unit beds and greater number of ventilators, as compared to developing nations of South Asia and Africa. A significant proportion of our population live in slums, where it is not possible to maintain adequate social distancing and practice frequent hand washing, the two key measures recommended to prevent the infection from spreading. Dr. Banerjee has highlighted three main reasons for lower death rates in South Asian and African countries: (i) lower median age of the population, (ii) lesser prevalence of overweight and obesity, and (iii) immunity acquired due to prior corona virus infections. However, a few other factors have also been hypothesized to be responsible for lower infection and death rates among South Asian population.
Higher temperatures and greater humidity: South Asian and African nations have a comparatively higher temperatures and greater humidity as compared to the European countries and the USA. A cross-sectional study looked at the effect of temperature on the cumulative number of Covid-19 cases in 429 cities from 27 countries, mainly China. The study found that for every 1°C rise in temperature, the number of cases reduced by 0.86.
Bacille Calmette–Guerin (BCG) vaccination is universally practiced in many South Asian and African countries, including India. BCG vaccine is known to have immunomodulatory properties. Previous studies have shown that BCG vaccination reduces the incidence of respiratory infections as well as deaths due to pneumonia and sepsis. BCG vaccination has been postulated to reduce viremia after severe acute respiratory syndrome coronavirus 2 (SARS-CoV2) exposure, resulting in less severe Covid-19 disease, lesser deaths, and faster recovery. Clinical trials are underway to test this hypothesis.
SARS CoV2 is an RNA virus and is characterized by high mutation rates. A recent study showed 8 novel recurrent mutations in SARS CoV2. Authors postulated that the virus strains in North America, Europe, and Asia may be different and they all can co-exist. Hence, it is possible that virus strain causing COVID-19 in Asia and Africa are less virulent. Further studies are needed to confirm this hypothesis.
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| References|| |
Banerjee A. COVID-19: The curious case of the dog that did not bark. Med J DY Patil Vidyapeeth 2020;13:189-91. [Full text]
Wang M, Jiang A, Gong L, Luo L, Guo W, Li C, et al
. Temperature significant change COVID-19 transmission in 429 cities. MedRxiv 2020.02.22.20025791.
Curtis N, Sparrow A, Ghebreyesus TA, Netea MG. Considering BCG vaccination to reduce the impact of COVID-19. Lancet 2020;395:1545-6.
Pachetti M, Marini B, Benedetti F, Giudici F, Mauro E, Storici P, et al
. Emerging SARS-CoV-2 mutation hot spots include a novel RNA-dependent-RNA polymerase variant. J Transl Med 2020;18:179.