|Ahead of print publication
COVID-19: The curious case of the dog that did not bark
Vadisha Srinivas Bhat
Department of Otorhinolaryngology, KS Hegde Medical Academy, Mangalore, Karnataka, India
|Date of Submission||24-May-2020|
|Date of Decision||19-Jul-2020|
|Date of Acceptance||24-Jul-2020|
Vadisha Srinivas Bhat,
Department of Otorhinolaryngology, KS Hegde Medical Academy, Mangalore, Karnataka
Source of Support: None, Conflict of Interest: None
COVID-19, a pandemic caused by a novel coronavirus, originated in Wuhan, a city of China, has spread across all human boundaries. This disease appears more contagious but fortunately less fatal compared to severe acute respiratory syndrome (SARS) and Middle East respiratory syndrome, the two known coronavirus zoonotic diseases. The genome of the coronavirus causing COVID-19 has 82% resemblance with human SARS-coronavirus-2 (CoV) which caused 2003 SARS pandemic, and hence, it is named SARS-CoV-2.
A single case of SARS would infect about three secondary cases, in a society which has not implemented any preventive control measures. However, COVID-19 is more contagious than its predecessor, with an estimated R0 of 5.7 in China. The higher affinity of the SARS-CoV-2 virus particles to the receptor needed for the cell entry is proved to be the higher infectiousness of SARS-CoV-2 than the 2003 SARS virus.
However, epidemiologists have noticed some significant differences between the human-to-human transmissions of these two zoonotic diseases. Transmission of SARS occurred after a few days of illness, and the viral load was moderate during the early phases, with a peak 10 days after the infection. In contrast to this, in COVID-19, the virus is detected early in the disease, even before the onset of symptoms, or even in people without symptoms. Asymptomatic cases also can transfer the infection and cause disease, which is different from SARS-CoV. The viral shedding pattern of COVID-19 appears to be similar to that of influenza.
The SARS pandemic, which occurred between 2002 and 2003, spread in 26 countries, with 8437 people getting infected and causing 813 deaths. The disease was very well controlled through public health measures, such as contact tracing and isolation. However, in the case of COVID-19, the virus has been detected in some patients, even before the onset of symptoms, and even in asymptomatic carriers. The transmission of infection from person to person can occur early during the disease, and the strategy for screening and isolation needs to be planned accordingly. A combination of control measures such as early and active surveillance, quarantine of contacts, and strict social distancing measures is necessary to slow down or stop the spread of the disease. If these measures are not implemented effectively, the virus can spread rapidly and destabilize the healthcare systems.
Although SARS had a fatality rate of 10%, this was not uniform across the globe. The disease was centered in China, with a maximum number of cases infected. However, the case-fatality rate was maximum in Canada, where there were 38 deaths of the 250 affected people, and in Singapore, where 32 out of the 206 people succumbed to the disease. In India, there were three cases of SARS; all of them had a complete cure.
Similarly, the fatality of COVID-19, too, is not uniform. In contrast to what was anticipated, the disease is still in its milder form in India. As rightly mentioned by the author in the Editorial “COVID-19: The Curious Case of the Dog That Did Not Bark,” cross-immunity among caused by infection by other viruses can be an explanation for lower case fatality in India. “Why didn't the dog bark?” probably because no stranger was there in the scene. In general, estimates suggest that 2% of the population are healthy carriers of a coronavirus and that these viruses are responsible for about 5%–10% of acute respiratory infections.
Mortality due to COVID-19 is high among the people with comorbidities, the elderly being worse affected. Countries with a more upper mean age have been severely affected. In Italy, 23% of the population was aged 65 years or more, in 2019. The fatality due to COVID-19 is worse, nearly 15% in patients aged more than 80 years. India, with a median age of about 27 years, is better placed than many Western countries in this regard. Furthermore, the lesson learned from observing the situation in other countries benefitted India as the authorities had enough time to protect the vulnerable population. Imposing early lockdown was a reasonable effort that helped slow down the spread of the virus.
India is a country with diversity in geographic and sociocultural characteristics. The behavior of COVID-19 is not uniform all over India. There are gross differences among the states, with few states bearing the infection. Contact tracing and testing strategies can also be one of the reasons for the disparity. Even the case fatality is not uniform, the disease being aggressive in some states. India needs to be prepared for an increase in the number of cases, as people stranded in various countries are returning now. Already, a large number of passengers are tested positive and being observed in quarantine centers. The return of migrant workers between states, resulting increase in the number of new infections in the recipient states , is another challenge to the state authorities. However, the mere publication of these data without explanation can spread harmful myths and create misunderstanding among people, and this can be a hindrance in providing equal healthcare. There is a need to understand the reality and accommodate these migrant people appropriately, as, in any pandemic or natural calamities, the most marginalized society suffer to a greater extent than others. Appropriate measures to prevent the disease spread in overcrowded slums are challenging, which otherwise which can give rise to an explosion of the disease.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
| References|| |
Peiris JS, Chu CM, Cheng VC, Chan KS, Hung IF, Poon LL, et al
. Clinical progression and viral load in a community outbreak of coronavirus-associated SARS pneumonia: A prospective study. Lancet 2003;361:1767-72.
Chan JF, Kok KH, Zhu Z, Chu H, To KK, Yuan S, et al
. Genomic characterization of the 2019 novel human-pathogenic coronavirus isolated from a patient with atypical pneumonia after visiting Wuhan. Emerg Microbes Infect 2020;9:221-36.
Lipsitch M, Cohen T, Cooper B, Robins JM, Ma S, James L, et al
. Transmission Dynamics and control of severe acute respiratory syndrome. Science 2003;300:1966-70.
Sanche S, Lin YT, Xu C, Romero-Severson E, Hengartner N, Ke R. High Contagiousness and rapid spread of severe acute respiratory syndrome coronavirus 2. Emerg Infect Dis 2020;26:1470-7.
Wrapp D, Wang N, Corbett KS, Goldsmith JA, Hsieh CL, Abiona O, et al
. Cryo-EM structure of the 2019-nCoV spike in the prefusion conformation. Science 2020;367:1260-3.
Rothe C, Schunk M, Sothmann P, Bretzel G, Froeschl G, Wallrauch C, et al
. Transmission of 2019-nCoV infection from an asymptomatic contact in Germany. N Engl J Med 2020;382:970-1.
Tsang TK, Cowling BJ, Fang VJ, Chan KH, Ip DK, Leung GM, et al
. Influenza a virus shedding and infectivity in households. J Infect Dis 2015;212:1420-8.
Banerjee A. COVID19: The curious case of the dog that did not bark. Med J DY Patil Vidyapeeth 2020;13:189-91. [Full text]
Chen Y, Liu Q, Guo D. Emerging coronaviruses: Genome structure, replication, and pathogenesis. J Med Virol 2020;92:418-23.
Onder G, Rezza G, Brusaferro S. Case-Fatality Rate and Characteristics of Patients Dying in Relation to COVID-19 in Italy. JAMA. 2020;323:1775-6.
Chowkwanyun M. Racial health disparities and COVID19-Caution and context. N Engl J Med 2020; 383:201-203.